Syntaxonomic Diversity of Rocky Dry Grasslands of the Chrysopogono grylli-Koelerion splendentis Along the East Adriatic

Abstract

This paper presents a comprehensive revision of the dry grasslands, specifically the alliance Chrysopogono grylli-Koelerion splendentis within the order Scorzoneretalia villosae along the eastern Adriatic, aimed at developing a formalized classification of this vegetation type. The revision is based on 490 relevés, including 44 newly sampled from the loci classici of previously identified associations, alongside additional relevés from the phytosociological literature. Both hierarchical and non-hierarchical cluster analysis, as well as NMS ordination, were employed to delineate the main vegetation types. Although numerous associations have been described to date, several were found to be floristically similar and were subsequently merged. Ultimately, 15 associations and one plant community were identified, including the description of a new association, Sideritido purpureae-Asphodeletum ramosi, from Montenegro, along with four new subassociations. The associations of the Chrysopogono grylli-Koelerion splendentis predominantly occur in the sub-Mediterranean variant of the temperate bioclimate. While this study provides a comprehensive framework for the syntaxonomic diversity of this alliance, it also underscores the need for additional phytosociological data from poorly known areas within its distribution range, particularly in the southernmost regions and inland areas (e.g., Albania, Bosnia and Herzegovina).

1. Introduction

The publication of the EuroVegChecklist (EVC) [1] and its subsequent recognition as the standard phytosociological classification of European vegetation by the International Association for Vegetation Science [2] are pivotal achievements in European syntaxonomy. The EVC establishes a comprehensive framework for classifying European vegetation up to the alliance level. Furthermore, any proposed updates can be officially reviewed by international expert groups through collaborative efforts, thus reducing the interpretative fragmentation that has historically occurred across different parts of Europe [2,3,4]. The EVC identifies over eleven hundred vascular plant-dominated alliances, with the highest concentration in the southern regions of Europe, particularly along the Mediterranean fringe. Recent reviews have examined the distribution of these alliances [5] as well as their structural, ecological, and biogeographical attributes [6]. While these alliances offer a valuable overview of syntaxonomic diversity across Europe, finer syntaxonomic resolution is essential for practical applications such as nature conservation and biodiversity management. Thus, the next logical step for European Phytosociology is to refine the EVC’s syntaxonomic resolution to the association rank.

In Europe, the Balkan Peninsula hosts an exceptional level of biodiversity [7,8]. The Balkan grasslands, for instance, support a substantial share of the Mediterranean region’s overall biodiversity, making the conservation of these ecosystems a priority [9]. However, for certain alliances, comprehensive knowledge of their associations is still clouded by contrasting interpretations in the scientific literature and other inconsistencies, such as nomenclature issues. One such case is the alliance Chrysopogono grylli-Koelerion splendentis Horvatić 1973, coded as “FES-09A” in the EVC, representing the “Illyrian sub-Mediterranean rocky grasslands on shallow calcareous soils” [1,4]. This alliance spans a wide area of the western Balkans, including Italy, Slovenia, Croatia, Bosnia and Herzegovina, Montenegro, the Republic of North Macedonia, and Albania, while its occurrence in other Balkan countries is doubtful [5,10]. Originally described by Horvatić [11], the alliance Chrysopogono grylli-Koelerion splendentis conceptually stems from the division of another alliance described (invalidly) ninety years ago, Chrysopogono grylli-Saturejion subspicatae Horvat et Horvatić 1934 [12,13]. Despite numerous studies on the associations ascribed to the Chrysopogono grylli-Koelerion splendentis over this extensive time span (e.g., [14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47]), significant gaps remain in the literature, with uncertainties warranting further exploration to enhance our understanding of its syntaxonomic diversity. Assigning new phytosociological relevés to existing or new associations often relied on author expertise rather than comprehensive numerical comparisons of phytosociological tables. Furthermore, most synopses of the alliance address associations only in parts of the alliance’s range (e.g., [19,34,48,49,50]), leaving unresolved relationships among associations described in different areas. The inconsistent application of phytosociological nomenclature rules [13] further complicates the ecological and floristic boundaries among the associations.

This paper aims to provide an in-depth and updated analysis of the associations of the Chrysopogono grylli-Koelerion splendentis through a critical review of the existing literature, integration of recent and new data, and numerical comparisons of phytosociological tables across the entire alliance range. This revision has important implications for both the understanding of the syntaxonomic and ecological patterns of the alliance and practical applications. An assessment of the syntaxonomic diversity of this alliance, indeed, may provide valuable insights for biodiversity management and the conservation of its habitats.

2. Materials and Methods

The dataset consists of 490 phytosociological relevés (Figure 1). Among these relevés, 446 have been previously documented in the scientific literature (Supplementary S1) while 44 are newly collected and are referred to here as ‘new relevés’ (Supplementary S2 and S3). These new relevés were sampled in the loci classici of the associations classified in the alliance “Chrysopogono grylli-Saturejion subspicatae Horvat et Horvatić ex Černjavski, Grebenščikov et Pavlović 1949” by Terzi [10], which corresponds to the Chrysopogono grylli-Koelerion splendentis [4]. Forty-four new relevés were sampled, four for each association, between May and June 2022, following the Braun-Blanquet approach [51]. Plot size was set at 25 m² (5 m × 5 m), and a complete inventory of vascular plants was recorded, along with key ecological and physiographic variables, including total vegetation cover, exposure, slope, percentage of rock outcrops, and stoniness (percentage of stone cover). The cover-abundance values of vascular plants were visually estimated using the 1–9 point numerical scale proposed by van der Maarel [52].

The term locus classicus refers to the area where the type-relevé of each association was originally sampled (Supplementary S2). For associations lacking a nomenclatural type, new relevés were sampled in the area of the original diagnosis. Unfortunately, certain associations, such as Narcisso-Asphodeletum microcarpi [23,24] and Salvio officinalis-Euphorbietum fragiferae [17], could not be sampled because they no longer exist in their loci classici due to construction or vegetation succession. Nonetheless, relevés from these associations are available in the literature (Supplementary S1). The association Festuco-Linetum flavi [53] is instead entirely absent from the dataset, as new relevés for this association could not be sampled due to the potential presence of landmines in its locus classicus from the Bosnian War (1992–1995), as advised by local authorities. No new relevés were collected for the Brachypodio retusi-Salvietum officinalis and Helichrysetum italici, as recent papers already include relevés sampled with the same methodology [46,47].

Although it cannot be stated with absolute certainty that the environmental conditions of the loci classici have remained unchanged over time, the structure and specific composition of the current vegetation, as recorded in the new relevés, suggest that they belong to the same associations as the nomenclatural types sampled in the past. This assumption was confirmed by the results of cluster analysis (Supplementary S6). Therefore, the new relevés ensure that each association is represented by at least four relevés, sampled using a consistent methodology (e.g., identical plot size), which are valuable for both this syntaxonomic revision and future applications, such as biodiversity monitoring plans.

The entire dataset, comprising new and previously documented relevés, contains 713 taxa. Plot sizes were available for 93% of the relevés, with a median size of 50 m², and most ranging from 25 m² (5th percentile) to 200 m² (95th percentile). All relevés were retained to avoid losing nearly the entire original diagnosis of the Bromo-Chrysopogonetum grylli, which included larger plot sizes. Taxa recorded only at the genus level were excluded as well as bryophytes and lichens, which were inconsistently recorded (see also [54]). Taxonomic nomenclature follows Euro + Med [55] with a few exceptions. Koeleria splendens was treated according to its traditional concept due to the lack of a comprehensive taxonomic revision across southern Europe and contrasting taxonomic treatments (cf. [55,56]). Bromopsis erecta was used to refer to a group of related species (e.g., Bromopsis condensata, Bromopsis erecta) that are not consistently distinguished in phytosociological literature. Festuca illyrica and Festuca stricta subsp. sulcata were treated under the same tag (i.e., Festuca stricta subsp. sulcata) due to their biometric similarity [57]. Syntaxonomic nomenclature follows FloraVeg.EU [4] and Terzi [10,13], except where indicated. Although several different syntaxonomic frameworks have been proposed for the Chrysopogono grylli-Koelerion splendentis (e.g., [11,46,58])—one of which includes two authors of this paper—this revision refrains from addressing this question, focusing instead on the lower syntaxonomic ranks and referring to the syntaxonomic scheme of the standard European vegetation classification [4].

Geographical coordinates (WGS84) were assigned to each relevé in the dataset, either sourced from the original publication or approximated based on location descriptions. These coordinates enabled the extraction of climatological data, including average monthly precipitation and temperatures for the period 1994–2023, derived from the TerraClimate dataset [59] and retrieved using Google Earth Engine [60]. Climatic data were employed to compute bioclimatic indices following the bioclimatic classification proposed by Rivas-Martinez et al. [61]. Specifically, the following bioclimatic indices were calculated for each relevé locality: yearly average temperature (Tmean), yearly positive precipitation (Pp), yearly positive temperature (Tp), continentality index (Ic), compensated thermicity index (Itc), ombrothermic index (Io), ombrothermic index of the warmest bimonth (Ios2), and summer compensated ombrothermic indexes (Ios3, Ios4).

The frequency and severity of disturbance in the sampled plant communities were estimated for all relevés in the dataset using the disturbance indicator values proposed by Midolo et al. [62]. Although these values were not available for all species, the species lacking these indicators had low frequency, so the available disturbance indicator values were used with the understanding that minor inaccuracies might be present. Additionally, life-form spectra weighted by taxon scores were calculated for all relevés based on data from Flora d’Italia [63,64,65] and the Flora Croatica Database [56].

To minimize redundancy among variables (bioclimatic variables, disturbance values, and life-forms), a correlation chart was generated (Supplementary S4). Only one variable from those exhibiting high correlation (r > 0.75) was retained. The retained variables include: phanerophytes, hemicryptophytes, geophytes, chamaephytes, therophytes, disturbance severity, disturbance frequency, continentality index, and ombrothermic index (positively correlated with Pp, Ios3, Ios4, and negatively correlated with Tmean, Tp and Itc), ombrothermic index of the hottest two months of the summer quarter (positively correlated with Ios3 and Ios4).

Data Analysis

Taxon scores originally recorded using the Braun-Blanquet scale (r, +, 1, 2, 3, 4, 5) or its extended form with the subdivision of “2” into three categories (2m, 2a, and 2b) [52] were converted to the percentage midpoints of the estimated cover classes. Specifically, cover percentages such as 1%, 2%, 3%, 13%, 38%, 63%, and 88% were used for the Braun-Blanquet scale, while scores 2m, 2a, and 2b were replaced with 4%, 8%, and 18%, respectively [66].

The relevés were subjected to agglomerative cluster analysis using Ward’s and the Flexible Beta methods, setting β = −0.25, on a Chord distance matrix. Prior to clustering, taxon scores underwent power (i.e., y′ = y^w) and logarithmic [y′ = log (y + 1)] transformations to reduce the influence of total coverage alone on clustering. Without any transformation, the resulting classification would be predominantly influenced by dominant species. Conversely, a drastic transformation (i.e., presence/absence) would result in a loss of information regarding taxon covers. Tichý et al. [66] found that the optimal power transformation for treating phytosociological data had exponents from 0.3 to 0.6. Accordingly, the dataset underwent seven power transformations with the following exponent values: 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, and 0.60.

Sixteen clustering solutions were derived from eight transformations and two clustering methods. For each dendrogram, the number of indicator species (IndSp) was calculated for taxa occurring in at least three relevés across the first 50 partitioning levels. These levels, ranging from two to fifty clusters, were examined as further partitions typically represent minor variations. Indicator species analysis (ISA) [67,68] was used to identify the indicator species (IndSp) associated to the clusters at each partitioning level. ISA is based on the Indicator Value index (IndVal), which measures the association between a taxon and a group of relevés (i.e., a dendrogram cluster). Each taxon was assigned to the cluster for which it yielded the highest IndVal. The IndVal was tested using a Monte Carlo permutation test with 1000 permutations (p < 0.05) to identify the IndSp. The partitioning level yielding the highest number of IndSp was used to select the optimal clustering solution and to prune the corresponding dendrogram [10,69,70]. After selecting the optimal dendrogram, the IndSp associated with the clusters at each partitioning level, up to the point where the dendrogram was pruned, was considered. However, to enhance the clarity of the results, each IndSp was associated with only one cluster—specifically, the cluster where it first reached its maximum value along the descending typology (Supplementary S6).

A challenge of agglomerative algorithms is that they may prevent a relevé already included in a group from being moved to another group appearing later in the agglomerative process, even if it would be more appropriate [71]. To optimize the classification obtained by agglomerative clustering, K-means partitioning was performed using taxa means for each of the main clusters as starting points [71].

Non-Metric Multidimensional Scaling (NMS) ordination was used to visualize the relationships among the major clusters of relevés. The bioclimatic, life-form, and disturbance-related variables were passively projected into the ordination space to highlight the most important environmental gradients, with a cut-off level at r² = 0.2 [69]. Box plots were used to display statistical summaries of some variables among the main groups.

Ideally, it would be possible to identify 15 main clusters corresponding to the 13 associations outlined by Terzi [8] for the Chrysopogono grylli-Koelerion splendentis (excluding the Festuco-Linetum flavi, which is not represented in the dataset), plus the additional two associations described later (Brachypodio retusi-Salvietum officinalis and Helichrysetum italici), with each cluster grouping all relevés previously assigned to the corresponding association. Although this ideal scenario was not fully realized, a cluster composed predominantly of relevés already assigned to a single association suggests that the cluster is consistent with previous interpretations (Supplementary S6). If it includes the nomenclatural type of that association, it is assigned accordingly, otherwise it represents a new syntaxonomic unit.

Based on the results of cluster analysis, ordination, and indicator species analysis (ISA), and considering both previous assignments of relevés and the presence of nomenclatural types in each cluster, the clusters were interpreted from a syntaxonomic perspective to identify the associations of the Chrysopogono grylli-Koelerion splendentis represented in our dataset (Supplementary S6). Once the associations were identified, each was characterized by: (i) diagnostic taxa (obtained via ISA, and represented by indicator species with IndVal > 20); (ii) dominant taxa (i.e., taxa with an average cover > 5%; the absence of a taxon was considered as having a value of zero in the calculation of averages); (iii) constant taxa (i.e., taxa with frequency > 60%); (iv) additional information concerning distribution range, environmental conditions, and nomenclature. All the nomenclatural decisions were taken based on the 4th edition of the International Code of Phytosociological Nomenclature (ICPN) [72]. In the synoptic table, characteristic and differential taxa of each association were selected by considering a broader context, beyond the results of the ISA, which is limited to the specific dataset (Supplementary S6 and S8).

All analyses, except for ordination, were conducted using the software R version 4.4.0 [73] with the packages vegan [74], cluster [75], indicspecies [68], tidyverse [76], labdsv [77], and PerformanceAnalytics [78]. Ordination was performed using PC-ORD, version 6.22, employing the “slow and thorough” option of the autopilot mode [79].

3. Results

The optimal clustering solution was achieved using Ward’s method on a Chord distance matrix, following a power transformation with an exponent of 0.3 (Figure 2).

The dendrogram was pruned at the 26th partitioning level, resulting In 26 main clusters of relevés. Additionally, a 27th cluster was considered, consisting of the four relevés of the Helichryso italici-Armerietum dalmaticae, which were grouped into a distinct subcluster (HA in Figure 2). The majority of these 27 main clusters were composed of relevés already classified within a single association (Supplementary S6). On average, nearly 90% of the relevés in each of these clusters belong to a single association based on their original assignment (Supplementary S1).

Based on the results of the indicator species analysis, the 27 main clusters (delineated on the left side of the dendrogram in Figure 2 by their contours) were grouped into 15 vegetation units, indicated in Figure 2 by two or three-letter codes, e.g., BS, SO, KFb (see Supplementary S6). The units BS and SO correspond to the chamaephytic associations Brachypodio retusi-Salvietum officinalis (BS) and Stipo-Salvietum officinalis (SO) and are separated in the upper part of the dendrogram. The other side predominantly comprises hemicryptophytic-chamaephytic associations. Those from the north Adriatic, NE Italy, Istria, and Kvarner (Figure 2, cluster II), with an oceanic temperate climate, are separated from those primarily thriving southwards, from Kvarner to Albania. In this latter group, associations from Mediterranean mountainous areas (clusters IIIa) are distinguished from those at lower altitudes (IIIb and IIIc). Two plant communities, floristically well differentiated and characterized by the presence and abundance of Asphodelus ramosus (i.e., Narcisso-Asphodeletum microcarpi, NA, and Bromo-Chrysopogonetum grylli sensu Stanišić-Vujačić et al., 2022, BCs), are isolated in cluster IIIc.

The k-means clustering produced approximately the same clusters as Ward’s method with the exception of 27 relevés, which were reassigned to different main clusters, thereby improving the overall interpretation of the results. For instance, the nomenclatural type relevé of the Salvio officinalis-Seslerietum juncifoliae, initially classified with the relevés of the Koelerio macranthae-Brachypodietum retusi in the Ward clustering, was moved to the cluster containing the other relevés of its association.

The NMS ordination (Figure 3) yielded a three-dimensional solution with a final stress of 18.8, accounting for 66.7% of the variance (axis 1: 29.5%, axis 2: 20.6%, and axis 3: 16.6%). The relevés do not show clear-cut discontinuities in the ordination space, although the main groups of relevés resulting from the cluster analysis (i.e., clusters Ia, Ib, II, IIIa, IIIb, and IIIc) are concentrated in different parts of the ordination space. For example, relevés of clusters Ia (empty circles in Figure 3a) and Ib (filled circles) are concentrated on the left side of the ordination diagram and are characterized by a predominance of chamaephytes, with Salvia officinalis being the main indicator species (IndSp) of these associations.

On the right side of the ordination diagram, relevés from the North Adriatic (cluster II, filled triangles in Figure 3a), those from the South (IIIa + IIIb, empty triangles in Figure 3a), and the two associations with Asphodelus ramosus (IIIc, empty squares in Figure 3a) are distinguished along axis 2. The main gradients along axis 1 (Figure 3b) involve the percentages of hemicryptophytes (Hw) and disturbance frequency (DF). Chamaephytes (Cw) are negatively correlated with axis 1 and are more represented in associations with Salvia officinalis. Axis 2, on the other hand, shows a positive correlation with therophytes (Tw) and disturbance severity (DS).

A more detailed analysis of the variations in biological forms (Supplementary S5), climatic variables, and disturbance indicators for the 15 identified vegetation units shows that the highest percentages of chamaephytes occur not only in the associations Brachypodio retusi-Salvietum officinalis (“BS” in Figure 2) and Stipo-Salvietum officinalis (SO) but also in two other vegetation types dominated by Helichrysum italicum, found on two islands (Plavnik and Pag Islands, respectively): Helichrysetum italici (HE) and Helichryso italici-Armerietum dalmaticae (HA). These same associations, along with Bromo erecti-Chrysopogonetum grylli sensu Stanišić-Vujačić et al., 2022 (BCs) and Narcisso tazettae-Asphodeletum microcarpi (NA), also exhibit the lowest percentages of hemicryptophytes. The highest percentages of therophytes are recorded in associations characterized by very severe disturbances, such as the Helichrysetum italici, Bromo erecti-Chrysopogonetum grylli sensu Stanišić-Vujačić et al., 2022, and Koelerio splendentis-Festucetum illyricae brachypodietosum retusi sensu Kamenjarin and Pavletić 2003 (KFb). The communities with the least frequent disturbances (presumably grazing, due to the presence of Salvia officinalis) are Brachypodio retusi-Salvietum officinalis, Salvio officinalis-Euphorbietum fragiferae, and Salvio officinalis-Seslerietum juncifoliae (SS).

From a bioclimatic perspective, the associations in the northern part of the distribution area of the alliance (Centaureo cristatae-Chrysopogonetum grylli, CC, Salvio officinalis-Euphorbietum fragiferae, SE, and Lactuco vimineae-Ischaemetum, LB) are characterized by lower summer aridity (and are thus not within the Mediterranean bioclimatic zone nor the sub-Mediterranean variant of the temperate bioclimate), along with the Festucetum illyrico-valesiacae (FI), which, being inland, show the lowest values of annual positive temperatures and of the compensated thermicity index. The lowest values of the ombrothermic index are recorded for the more Mediterranean associations, such as the Brachypodio retusi-Salvietum officinalis and Koelerio splendentis-Festucetum illyricae brachypodietosum retusi sensu Kamenjarin and Pavletić 2003, followed by the Salvio officinalis-Seslerietum juncifoliae. The highest value of the continentality index is recorded for the association Bromo erecti-Chrysopogonetum grylli sensu Stanišić-Vujačić et al., 2022 sampled near Podgorica, Montenegro. Photos of typical stands of associations are provided in Supplementary S7.

4. Discussion

Based on the results, the following associations and plant community have been recognized (see Supplementary S8):

• Brachypodio retusi-Salvietum officinalis (“BS” in Figure 2).

Dominant taxa (average cover, %): Salvia officinalis (19.5), Brachypodium retusum (11).

Diagnostic taxa: Brachypodium retusum.

Constant taxa (frequency, %): Brachypodium retusum (100), Salvia officinalis (100).

Description: This recently described association [44] corresponds to the Stipo-Salvietum officinalis var. Brachypodium retusum as defined by Horvatić [16]. It consists of a limited number of taxa and is characterized by the dominance of Brachypodium retusum and Salvia officinalis. Among the associations within the alliance Chrysopogono grylli-Koelerion splendentis, this chamaephyte-dominated community is found in the hottest and driest rocky habitats of the eastern Adriatic islands, specifically within the Kornati Archipelago and the nearby islands of the Middle Adriatic. This association thrives in a Mediterranean pluvio-seasonal oceanic bioclimate, with a mesomediterranean thermotype and a (upper) dry to (lower) subhumid ombrotype. The Brachypodio retusi-Salvietum officinalis is, therefore, the most xerothermic association of this alliance. It is also confined to the lowest altitudes, occurring exclusively in undisturbed sites, primarily in contact with coastal communities of the class Crithmo-Staticetea. Due to the successional pathway, several species of the class Quercetea ilicis are found in the relevés of this association.

• Stipo-Salvietum officinalis (“SO” in Figure 2).

Dominant taxa: Salvia officinalis (35.7), Bromopsis erecta (9.2), Stipa eriocaulis (6.6), Festuca stricta subsp. sulcata (5.1).

Diagnostic taxa: Salvia officinalis, Micromeria juliana, Campanula lingulata (Stipo-Salvietum officinalis campanuletosum lingulatae), Asperula scutellaris (Stipo-Salvietum officinalis campanuletosum lingulatae), Clinopodium suaveolens (Stipo-Salvietum officinalis campanuletosum lingulatae).

Constant taxa: Salvia officinalis (98.1), Bromopsis erecta (82.4), Teucrium capitatum subsp. capitatum (71.3), Koeleria splendens (63).

Description: Stands of this chamaephytic community cover extensive areas from the Kvarner region (Croatia) to Montenegro and Northern Albania, under sub-Mediterranean conditions where Salvia officinalis is the primary dominant taxon, followed by Bromopsis erecta. The Stipo-Salvietum officinalis occupies unfavorable habitats of bare karst on very shallow soils throughout its distribution range. Although this community experiences relatively low disturbance frequency and intensity compared to other associations of the alliance, it can nonetheless lead to scrub and forest stages along the successional pathway [80]. Indeed, the relevés of this association often include several species of the classes Ononido-Rosmarinetea and Quercetea pubescentis. The Stipo-Salvietum officinalis occurs within the sub-Mediterranean variant of the temperate macrobioclimate. Relevés from Montenegro have previously been classified under the subassociation campanuletosum lingulatae due to the presence of Campanula lingulata, Asperula scutellaris, and Clinopodium suaveolens [46]. This subassociation is characterized by an oceanic-continental temperate bioclimate and a (lower and upper) humid ombrotype. The typical subassociation, found in the northern part of the association’s range, is characterized by an oceanic-temperate bioclimate, with a mesotemperate-supratemperate thermotype and a (upper) subhumid to (lower) humid ombrotype. The typical subassociation is also represented in our dataset by some relevés that were previously included in the Helichrysetum italici salvietosum officinalis, Festuco-Koelerietum splendentis, and “Brometo-Chrysopogonetum grylli asphodeletosum microcarpi” (see Supplementary S6), with which it shares similar floristic and ecological characteristics.

• Koelerio splendentis-Festucetum illyricae brachypodietousm retusi sensu Kamenjarin and Pavletić 2003 (“KFb” in Figure 2).

Dominant taxa: Brachypodium retusum (22.1).

Diagnostic taxa: Festuca dalmatica.

Constant taxa: Brachypodium retusum (100), Bupleurum veronense (100), Carthamus lanatus (90.9), Festuca dalmatica (90.9), Koeleria splendens (81.8), Avena fatua (72.7), Carduus nutans subsp. micropterus (72.7), Dactylis glomerata subsp. hispanica (72.7), Dorycnium hirsutum (72.7), Hypericum perforatum (72.7), Koeleria macrantha (72.7), Salvia officinalis (72.7), Asparagus acutifolius (63.6), Briza maxima (63.6), Teucrium capitatum subsp. capitatum (63.6).

Description: The Koelerio splendentis-Festucetum illyricae brachypodietosum retusi was first described in the Šibenik area (Croatia) as a subassociation of the Koelerio splendentis-Festucetum illyricae with Brachypodium retusum, found on gently sloping, west-facing slopes with red-brown soils [35]. Later, Kamenjarin and Pavletić [38] also assigned some dry grasslands from the Island of Čiovo to this subassociation, with their relevés included in dendrogram cluster KFb (Figure 2). However, these grasslands are quite distinct from those in the Šibenik area due to the absence of typical grassland hemicryptophytes such as Chrysopogon gryllus, Festuca valesiaca, and Bromopsis erecta, and the presence of Festuca dalmatica, Koeleria macrantha, Salvia officinalis, and Gelasia villosa subsp. villosa. Therefore, they cannot be classified within the Koelerio splendentis-Festucetum illyricae (i.e., Bromo-Chrysopogonetum grylli; see below). In addition to these floristic distinctions, the stands from the island of Čiovo were recorded in an area characterized by a typical Mediterranean pluvio-seasonal bioclimate, mesomediterranean thermotype, and lower subhumid ombrotype. In contrast, the Koelerio splendentis-Festucetum illyricae is primarily associated with the sub-Mediterranean variant of the temperate-oceanic bioclimate, with a subhumid to humid ombrotype. The stands on the island of Čiovo occur at low altitudes in a transitional zone, possibly between the Stipo-Salvietum officinalis, Koelerio macranthae-Brachypodietum retusi, and other grasslands of the class Lygeo-Stipetea. Festuca dalmatica is the only diagnostic species of this vegetation type, which is either dominated or co-dominated by Brachypodium retusum. Due to its heterogeneity and intermediate position between other associations, we have refrained from assigning it a formal syntaxon name, instead referring to it as the Festuca dalmatica-Brachypodium retusum plant community. Further data from additional localities are needed to determine its syntaxonomic status.

• Centaureo cristatae-Chrysopogonetum grylli (“CC” in Figure 2).

Dominant taxa: Bromopsis erecta (17.8), Chrysopogon gryllus (11.2), Carex humilis (8.7), Satureja montana (7.6).

Diagnostic taxa: Carex humilis, Dorycnium pentaphyllum subsp. germanicum, Centaurea cristata, Asperula purpurea, Globularia bisnagarica, Leontodon saxatilis, Veronica barrelieri, Allium carinatum subsp. pulchellum, Jacobaea vulgaris.

Constant taxa: Bromopsis erecta (98.3), Eryngium amethystinum (91.4), Satureja montana (91.4), Teucrium montanum (91.4), Carex humilis (89.7), Dorycnium pentaphyllum subsp. germanicum (89.7), Chrysopogon gryllus (87.9), Thymus longicaulis subsp. longicaulis (86.2), Bothriochloa ischaemum (70.7), Convolvulus cantabrica (70.7), Salvia pratensis (69), Thesium divaricatum (67.2), Asperula cynanchica (65.5), Centaurea cristata (65.5), Euphorbia cyparissias (62.1), Genista sylvestris (60.3).

Description: The Centaureo cristatae-Chrysopogonetum grylli was originally described for the dry grasslands of the Isontine Karst, near Gorizia and Monfalcone (Italy) [16]. Its distribution range was later expanded to include the Triestine Karst in Italy, as well as some localities in Slovenia and Croatia extending toward Istria [34]. Poldini [34] combined two other associations he had described earlier—Seseli gouanii-Artemisietum albae [30] and Lactuco vimineae-Ischaemetum [28]—under the Centaureo cristatae-Chrysopogonetum grylli, reducing them to the rank of subassociations (i.e., genistetosum sericeae Poldini 1989 and sedetosum sexangulari Poldini 1989, respectively). Our results support maintaining the Lactuco vimineae-Ischaemetum and the Centaureo cristatae-Chrysopogonetum grylli as separate associations. The latter consists of three subassociations. The typical subassociation corresponds to the concept originally proposed by Ferlan and Giacomini [16]. The subassociation Centaureo cristatae-Chrysopogonetum grylli genistetosum sericeae, with Genista sericea as its main differential species, includes several relevés and, among them, the nomenclatural type of the association Seseli gouanii-Artemisietum albae. Consequently, this latter association was united with the Centaureo cristatae-Chrysopogonetum grylli and lowered to the rank of subassociation (i.e., C.c.-C.g. genistetosum sericeae), retaining its nomenclatural type (i.e., rel. 2, Table 14, page 105, in [30]), and original diagnosis (i.e., Table 14, page 105, in [30]), according to Art. 27c ICPN. The cluster of this association (labeled “CC” in Figure 2) also includes a subcluster representing the Saturejo montanae-Ischaemetum Horvat in Horvat, Glavač et Ellenberg 1974 [48], with only the four relevés we sampled in Kukuljanovo, near Rijeka in Croatia. These relevés are floristically poorly differentiated from others in the cluster, but they are characterized by the absence of some diagnostic species of the association (e.g., Centaurea cristata, Asperula purpurea, Leontodon saxatilis, Jacobaea vulgaris, Veronica barrelieri, Allium carinatum subsp. pulchellum) and by the presence or higher frequency of others (e.g., Festuca stricta subsp. sulcata, Centaurea rupestris, Rhamnus intermedia). Consequently, the Saturejo montanae-Ischaemetum is here considered a subassociation of the Centraureo cristatae-Chrysopogonetum grylli (i.e., rhamnetosum intermediae subass. nov.). However, additional relevés are required to more accurately assess its syntaxonomic position. The association name Saturejo montanae-Ischaemetum is formed from the specific epithet “ischaemum” without the generic name “Bothriochloa”. Since the association name was published before 1979 [13], it is valid under Art. 14b ICPN. However, since Ischaemum is also a generic name validly published (“Ischaemum L., Sp. Pl. [Linnaeus] 2: 1049 (1753)”) [81], the association name must be retained in its original form (Art. 14b). Since this association is here lowered to the rank of subassociation (i.e., Centraureo cristatae-Chrysopogonetum grylli rhamnetosum intermediae subass. nov.), its original diagnosis, i.e., column n. 26, Table 42, p. 208, in [48], remains unaltered (Art.27c). Here, we designate rel. n. 34 in Supplementary S3 (reported in the Appendix A) as the neotypus of the Saturejo montanae-Ischaemetum and consequently of the Centraureo cristatae-Chrysopogonetum grylli rhamnetosum intermediae. The Centaureo cristatae-Chrysopogonetum grylli thrives in the supratemperate belt of the temperate oceanic bioclimate, with a (lower) humid ombrotype for the typical subassociation and a humid-hyperhumid ombrotype for the other two subassociations. Although this association is not subjected to climatic aridity, it does experience edaphic aridity. As noted by Poldini [34], it is one of the most xerothermic associations of the Scorzoneretalia villosae in the Isontine and Triestine Karst.

• Salvio officinalis-Euphorbietum fragiferae (“SE” in Figure 2).

Dominant taxa: Teucrium flavum (5.3), Salvia officinalis (5.2).

Diagnostic taxa: Teucrium flavum, Euphorbia fragifera, Alyssum austrodalmaticum (incl. A. montanum auct.), Campanula sibirica, Seseli kochii.

Constant taxa: Satureja montana (100), Euphorbia fragifera (93.3), Teucrium flavum (93.3), Salvia officinalis (86.7), Dactylis glomerata subsp. glomerata (80), Alyssum austrodalmaticum (66.7), Silene vulgaris (66.7), Stachys recta s.l. (66.7).

Description: This association was originally described for plant communities with Salvia officinalis and Euphorbia fragifera occurring on eroded soil covered with stones (locally called “grize”), from the Trieste Karst, Italy [17]. Poldini [34] considered this association a synonym of the Stipo-Salvietum officinalis. Although there are some similarities between these two syntaxa, in this study, the Salvio officinalis-Euphorbietum fragiferae is treated as an autonomous association, as comprehensively elaborated by Terzi [10] and Terzi et al. [46]. During our survey in the area where the association was originally described [17], we were unable to locate substantial stands of this association, finding only very small patches within forested areas (Supplementary S7). Like the previous association, the Salvio officinalis-Euphorbietum fragiferae thrives in a temperate oceanic bioclimate, with a supratemperate thermotype and a (lower) humid ombrotype.

• Lactuco vimineae-Ischaemetum (“LB” in Figure 2).

Dominant taxa: Bothriochloa ischaemum (35), Satureja montana (7.8), Cleistogenes serotina (6.4).

Diagnostic taxa: Cleistogenes serotina, Asperula aristata (diff. Lactuco vimineae-Bothriochloetum ischaemum helichrysetosum italici), Odontites luteus (diff. Lactuco vimineae-Bothriochloetum ischaemum helichrysetosum italici), Helichrysum italicum (diff. Lactuco vimineae-Bothriochloetum ischaemum helichrysetosum italici).

Constant taxa: Bothriochloa ischaemum (93.2), Satureja montana (93.2), Eryngium amethystinum (77.3), Sanguisorba minor (77.3), Cleistogenes serotina (70.5), Koeleria splendens (61.4).

Description: The association Lactuco vimineae-Ischaemetum was described for a specific type of grassland dominated by Bothriochloa ischaemum and Cleistogenes serotina, thriving on sloped surfaces subject to summer edaphic aridity along the Triestine Karst in Italy [28]. In this area, the Lactuco vimineae-Ischaemetum occurs within the temperate oceanic bioclimate, characterized by a supratemperate thermotype and mostly humid ombrotype. Poldini [34] later lowered this association to the rank of subassociation under the Centaureo cristatae-Chrysopogonetum grylli. However, our results indicate that it can be considered an autonomous association, as previously proposed by Zanatta [82]. Additionally, our findings support the merging of the Lactuco vimineae-Ischaemetum with the Dichanthio ischaemum-Cleistogenetum serotinae from the islands of Krk and Lošinj in Croatia [21,22]. These two associations share several species (see Supplementary S6) and their clusters in the dendrogram converge to form a single unit (“LB” in Figure 2). Consequently, the Dichanthio ischaemum-Cleistogenetum serotinae is reduced to the rank of subassociation, Lactuco vimineae-Ischaemetum helichrysetosum italici, distinguished by the absence of certain species (e.g., Asperula purpurea, A. cynanchica, Lactuca viminea, Fumana procumbens) and a higher frequency of others such as Asperula aristata, Odontites luteus, and Helichrysum italicum. This subassociation occurs to the south of the typical one, under a sub-Mediterranean variant of the temperate oceanic bioclimate, characterized by a mesotemperate-supratemperate thermotype and a (upper) subhumid to (lower) humid ombrotype. The floristic relationships between these two associations had already been noted by Poldini [28], albeit with different interpretations of the syntaxonomic framework.

The association name Lactuco vimineae-Ischaemetum is formed from the specific epithet “ischaemum” without the generic name “Bothriochloa”. Since the association name was validly published before 1 Jan 1979 [13], it is valid under Art. 14b ICPN. Being Ischaemum also a valid generic name, as written above, the association name must be retained in its original form (Art. 14b). The association name Dichanthio ischaemum-Cleistogenetum serotinae was validly published by Poldini [28] with an original diagnosis consisting of a synoptic table, i.e., col. 2, Table III, page 95, in [28], derived from relevés originally sampled on the island of Krk, Croatia, by Trinajstić [21]. Here we designate the rel. n. 13 in Supplementary S3 (also reported in the Appendix A), from the island of Krk, as the neotypus of the Dichanthio ischaemum-Cleistogenetum serotinae. This association is lowered to the rank of subassociation under the Lactuco vimineae-Ischaemetum and therefore it retains its nomenclatural (neo) type and original diagnosis.

• Helichryso italici-Armerietum dalmaticae (“HA” in Figure 2).

Dominant taxa: Artemisia alba (30.5), Helichrysum italicum (28), Bromopsis erecta (11), Stipa eriocaulis (9).

Diagnostic taxa: Dianthus ciliatus subsp. ciliatus, Peucedanum cervaria, Armeria canescens subsp. Dalmatica.

Constant taxa: Armeria canescens subsp. dalmatica (100), Artemisia alba (100), Bupleurum veronense (100), Eryngium amethystinum (100), Helichrysum italicum (100), Silene vulgaris (100), Stipa eriocaulis (100), Bromopsis erecta (75), Dianthus ciliatus subsp. ciliatus (75), Dorycnium hirsutum (75), Echinops ritro (75), Leontodon crispus (75), Orobanche gracilis (75), Peucedanum cervaria (75), Sanguisorba minor (75).

Description: The Helichryso italici-Armerietum dalmaticae was originally described from the island of Pag [14,19]. The stands of this chamaephyte-dominated vegetation develop on relatively deep and dry gravelly-loamy limestone soils. Currently, this association is known only from the island of Pag, where it primarily covers surfaces of abandoned vineyards near the seacoast. It occurs under a highly strong sub-Mediterranean variant of the temperate oceanic bioclimate, with a mesotemperate thermotype and a (upper) subhumid ombrotype. Although diagnostic taxa exhibit lower IndVal scores, this vegetation is characterized by a well-defined floristic composition and structure, dominated by Artemisia alba and Helichrysum italicum (see Supplementary S7), as already observed on page 358 by Horvatić [14]. Therefore, the Helichryso italici-Armerietum dalmaticae is here considered an autonomous association. The original diagnosis of the Helichryso italici-Armerietum dalmaticae consists of a synoptic table [19] (page 79); therefore, we designate rel. 23 in Supplementary S3 and Appendix A as the neotypus of the Helichryso italici-Armerietum dalmaticae. In addition, since Helichrysum italicum is more abundant than Armeria canescens subsp. dalmatica in the neotype, the association name has been reversed to Armerio dalmaticae-Helichrysetum italici.

• Salvio officinalis-Seslerietum juncifoliae (“SS” in Figure 2).

Dominant taxa: Sesleria juncifolia (30.1), Bromopsis erecta (14.5), Brachypodium retusum (13), Salvia officinalis (11.5), Genista sylvestris (5.6), Tanacetum cinerariifolium (5.4).

Diagnostic taxa: Sesleria juncifolia, Muscari botryoides, Tulipa sylvestris, Bunium alpinum subsp. montanum, Crepis dioscoridis.

Constant taxa: Brachypodium retusum (100), Bromopsis erecta (100), Salvia officinalis (100), Sesleria juncifolia (100), Muscari botryoides (90), Tanacetum cinerariifolium (80), Tulipa sylvestris (80), Bunium alpinum subsp. montanum (70), Genista sylvestris (70), Silene vulgaris (70).

Description: This Mediterranean-mountainous association was described for St. Nicholas Mountain on the island of Hvar and the central Pelješac Peninsula (Croatia), at an altitude of 550–630 m above sea level, on north-exposed slopes with humus-rich black skeletal soil [29]. The association thrives under a Mediterranean pluvio-seasonal oceanic bioclimate, with a mesomediterranean thermotype and a (lower) subhumid ombrotype. According to Trinajstić [50], this vegetation is more widely distributed in the Mediterranean-mountainous belt along the eastern Adriatic. The association shares some species with the Koelerio macranthae-Brachypodietum retusi, due to their proximity in altitudinal distribution and similar climatic conditions.

• Bromo erecti-Festucetum lapidosae (“BF” in Figure 2).

Dominant taxa: Festuca lapidosa (14.6), Festuca valesiaca (14.3), Bromopsis erecta (13.3), Thymus longicaulis subsp. longicaulis (9.3), Koeleria splendens (7.2).

Diagnostic taxa: Festuca lapidosa, Centaurea rupestris, Helianthemum italicum, Bunium ferulaceum.

Constant taxa: Bromopsis erecta (100), Eryngium amethystinum (100), Festuca lapidosa (100), Festuca valesiaca (100), Galium corrudifolium (91.7), Plantago holosteum (91.7), Teucrium capitatum subsp. capitatum (91.7), Genista sylvestris (83.3), Sanguisorba minor (83.3), Bunium ferulaceum (75), Centaurea rupestris (75), Koeleria splendens (75), Polygala nicaeensis (75), Trachynia distachya (75), Helianthemum italicum (66.7), Marrubium incanum (66.7).

Description: This Mediterranean-mountainous association was described for Vidova Gora Mountain on the island of Brač (Croatia), at an altitude of 400–700 m above sea level, on shallow, skeleton-rich soils [35]. The bioclimate is oceanic temperate in its sub-Mediterranean variant, with a meso-supratemperate thermotype and a subhumid ombrotype. The association is characterized by Festuca lapidosa, a relatively rare plant species in Croatia, primarily distributed on the islands of the mid-Adriatic and in Istria [56], and Centaurea rupestris. Other species, such as Edraianthus tenuifolius and Teucrium montanum, are diagnostic of the alliance Saturejion subspicatae. Additionally, the diagnostic taxa Helianthemum italicum and Bunium ferulaceum are also shared with the Koelerio macranthae-Brachypodietum retusi. Since Bromus erectus Huds. is replaced in several floras in current use (e.g., [54,62]) by Bromopsis erecta (Huds.) Fourr., the name Bromo erecti-Festucetum lapidosae is here mutated (Art. 45) with the alternative form Bromopsido erectae-Festucetum lapidosae.

• Koelerio macranthae-Brachypodietum retusi (“KB” in Figure 2).

Dominant taxa: Koeleria macrantha (16.9), Brachypodium retusum (12.9), Bromopsis erecta (8.7), Hyacinthella dalmatica (7.7).

Diagnostic taxa: Hyacinthella dalmatica, Koeleria macrantha, Iberis umbellata, Helianthemum italicum, Bunium ferulaceum.

Constant taxa: Anthyllis vulneraria (100), Brachypodium retusum (100), Bromopsis erecta (100), Euphorbia spinosa (100), Koeleria macrantha (100), Genista sylvestris (88.9), Helianthemum italicum (88.9), Teucrium capitatum subsp. capitatum (88.9), Eryngium amethystinum (77.8), Hyacinthella dalmatica (77.8), Tanacetum cinerariifolium (77.8), Cerastium ligusticum (66.7).

Description: This vegetation type occurs in southern Croatia at an altitude of 300–600 m above sea level, on shallow and slightly skeleton-rich soils [39]. This chamaephyte-hemicryptophyte association is characterized by the endemic western Balkan species Hyacinthella dalmatica and the circumboreal Koeleria macrantha, which is commonly found in a variety of mountain grassland associations across continental Europe. Among the diagnostic taxa, Helianthemum italicum and Bunium ferulaceum are shared with the Bromo erecti-Festucetum lapidosae. Additionally, due to the presence and (co)dominance of Bromopsis erecta and Brachypodium retusum, this association shows similarities with the Salvio officinalis-Seslerietum juncifoliae [46]. Terzi [13] considered the name Koelerio macranthae-Brachypodietum retusi Trinajstić 2005 to be invalid because, in its type relevé, i.e., rel. 1, Table 1, p. 351, in [39], Koeleria macrantha is dominant. According to the 3rd edition of the ICPN [83], a name published on or after 1 January 2002 that is formed from the names of two taxa is invalid if the dominant species appears first. However, according to the subsequent 4th edition of the ICPN [72], Art. 10b, such names are valid and legitimate and must be inverted according to Art. 42. Therefore, in this specific case, the association name is Brachypodio retusi-Koelerietum macranthae Trinajstić 2005 nom. invers.

• Helichrysetum italici (“HE” in Figure 2).

Dominant taxa: Helichrysum italicum (32.3), Salvia officinalis (7.6).

Diagnostic taxa: Sideritis romana subsp. romana (differential), Helichrysum italicum (differential), Sonchus bulbosus subsp. bulbosus (differential), Orobanche minor.

Constant taxa: Bromopsis erecta (100), Catapodium rigidum (100), Helichrysum italicum (100), Trifolium campestre (100), Linum trigynum (92.9), Trachynia distachya (92.9), Anagallis arvensis (85.7), Dactylis glomerata subsp. hispanica (85.7), Euphorbia exigua (85.7), Gastridium ventricosum (85.7), Koeleria splendens (85.7), Sideritis romana subsp. romana (85.7), Medicago minima (78.6), Valantia muralis (78.6), Trifolium scabrum (71.4), Carlina corymbosa (64.3), Euphorbia cyparissias (64.3), Linum tenuifolium (64.3), Reichardia picroides (64.3).

Description: This association was originally described from the island of Plavnik in the Kvarner region (Croatia) and is the earliest formally validly described association of the alliance Chrysopogono grylli-Koelerion splendentis [47,84]. In his subsequent works, Horvatić [14,15,19] did not mention Helichrysetum italici, which may have been considered included within the Bromo erecti-Chrysopogonetum grylli. However, our results demonstrate that the floristic composition of the Helichrysetum italici distinguishes this association from others in the alliance Chrysopogono grylli-Koelerion splendentis, despite the presence of only a few diagnostic species. The stands of this association occur on incoherent substrates in disturbed sites with high and peculiar grazing pressure, which aligns with the high proportion of annual species characteristic of the class Stipo-Trachynetea. Helichrysum italicum is the dominant species. Terzi and Jasprica [47] studied the ecology and syntaxonomy of the association and differentiated two subassociations: typicum and salvietosum officinalis. The latter is characterized by the presence and dominance of Salvia officinalis. The bioclimate of the island of Plavnik falls within the sub-Mediterranean variant of the oceanic temperate bioclimate, with a mesotemperate thermotype and a (upper) subhumid to (lower) humid ombrotype.

• Festucetum illyrico-valesiacae (“FI” in Figure 2).

Dominant taxa: Festuca stricta subsp. sulcata (31.2), Bromopsis erecta (8.4), Eryngium amethystinum (8), Salvia officinalis (7.4), Thymus longicaulis subsp. longicaulis (6.4), Potentilla tommasiniana (5.2).

Diagnostic taxa: Achillea nobilis, Potentilla tommasiniana, Trifolium repens, Centaurea jacea subsp. weldeniana, Filipendula vulgaris (diff.).

Constant taxa: Bromopsis erecta (100), Festuca stricta subsp. sulcata (100), Eryngium amethystinum (92.9), Festuca valesiaca (85.7), Sanguisorba minor (85.7), Thymus longicaulis subsp. longicaulis (85.7), Achillea nobilis (78.6), Asperula cynanchica (78.6), Sedum sexangulare (78.6), Lotus corniculatus (71.4), Plantago holosteum (64.3).

Description: This association was at first described by Horvat [80] as Festucetum pseudovinae-valesiacae and subsequently validated by Horvat [48]. The association name has been corrected by Trinajstić [36] due to the presence of Festuca illyrica instead of Festuca pseudovina (i.e., Festuca valesiaca subsp. parviflora). Among all the associations of the alliance studied here, Festucetum illyrico-valesiacae occurs within the temperate macrobioclimate or, at least, on the border between the Mediterranean mountainous belt and the inner slopes of the Dinarides in Croatia and Bosnia and Herzegovina [36]. The bioclimate is classified as oceanic temperate, characterized by a supratemperate thermotype and a (upper) humid to (lower) hyperhumid ombrotype. This association is distinguished by having the lowest values of thermicity and yearly positive temperature indexes, a lack of summer aridity, and a high frequency of disturbances compared to other associations in the alliance. It also exhibits a high proportion of hemicryptophytes. Consequently, the Festucetum illyrico-valesiacae has been regarded as a transitional community toward the more continental vegetation of the Festucetalia valesiacae [78]. Indicator species (IndSp) include Achillea nobilis and Potentilla tommasiniana, which are characteristic of this association. We were unable to find stands of this association in its locus classicus, but we did find small remnant patches along the road from Um (Podum) to Drenov Klanac, Lika, Croatia, on rocky substrates with thin soils. The syntaxonomic position of this association has been widely interpreted. Horvat [80] invalidly described a new suballiance, “Podsveza Festucion pseuovinae”, within the “Chrysopogoni-Satureion Horv. et H-ić 1934” to accommodate this association. This suballiance was later invalidly elevated to the rank of alliance by Ritter-Studnička [53], who also included the Festuco-Linetum flavi. The alliance was subsequently validated by Trinajstić [13,36]. More recently, Terzi [10] placed the Festucetum illyrico-valesiacae within the Chrysopogono grylli-Koelerion splendentis, and this framework is followed in this paper. Since in the association type relevé, Festuca illyrica is dominant, the association name is here inverted according Art. 42 ICPN.

• Bromo erecti-Chrysopogonetum grylli (“BC” in Figure 2).

Dominant taxa: Chrysopogon gryllus (16.9), Festuca valesiaca (12.2), Bromopsis erecta (12.1), Koeleria splendens (10.2), Helichrysum italicum (6.9).

Diagnostic taxa: Allium tenuiflorum (diff. subass.), Cytisus spinescens (diff. subass.), Fumana procumbens (diff subass.).

Constant taxa: Bromopsis erecta (90.4), Koeleria splendens (86.3), Chrysopogon gryllus (74), Festuca valesiaca (74), Eryngium amethystinum (72.6), Teucrium capitatum subsp. capitatum (67.1), Helichrysum italicum (63).

Description: The Bromo erecti-Chrysopogonetum grylli was originally described with two subassociations: dorycnietosum [14] (rels. 1–10, Table XXVIII) and asphodeletosum microcarpi [14] (rels. 11–25, Table XXVIII), both of which include several facies. The former subassociation was later elevated to the rank of association, named Ononido antiquorum-Brometum condensati, and reassigned to the alliance Scorzonerion villosae [19]. Most relevés (12 out of 15) from the asphodeletosum microcarpi were included in the original diagnosis of a new association, Asphodelo-Chrysopogonetum grylli Horvatić 1963, which is dominated by Chrysopogon gryllus and Bromopsis erecta and characterized by the presence of Asphodelus ramosus and Cytisus spinescens [19,85]. Of the remaining three relevés from the original diagnosis of the Bromo erecti-Chrysopogonetum grylli, two clearly belong to the Stipo-Salvietum officinalis, while the last one, i.e., rel. 17, Table XXVIII, in [14], was selected as the lectotype of the Bromo erecti-Chrysopogonetum grylli [13]. Since this relevé is similar to those of the Asphodelo-Chrysopogonetum grylli, Terzi [10] united the two associations, Asphodelo-Chrysopogonetum grylli and Bromo erecti-Chrysopogonetum grylli, under the earlier name (Bromo erecti-Chrysopogonetum grylli). Horvatić [19] restricted the distribution of the Asphodelo-Chrysopogonetum grylli to a few more degraded rocky areas in the northeastern Adriatic and described another association, Festuco-Koelerietum splendentis, an open hemicryptophytic community dominated by Koeleria splendens, Chrysopogon gryllus, and Festuca valesiaca, occurring in moderately disturbed sites [19]. This latter association is widespread across the Mediterranean and sub-Mediterranean belts of the east Adriatic. In our analysis, relevés originally ascribed to the Bromo erecti-Chrysopogonetum grylli, those later reclassified under Asphodelo-Chrysopogonetum grylli, and those assigned to Festuco-Koelerietum splendentis are grouped into three nearby clusters in the dendrogram. The floristic differences among these clusters are insufficient to distinguish three separate associations, leading us to consolidate them into a single association (Bromo-Chrysopogonetum grylli), which is now widespread along the east Adriatic and represents the principal association of the alliance. Since Bromus erectus Huds. is replaced in several floras in current use (e.g., [55,63]) by Bromopsis erecta (Huds.) Fourr., the name Bromo-Chrysopogonetum grylli [14] (p. 329) is here mutated (Art. 45) with the alternative form Bromopsido erectae-Chrysopogonetum grylli. This association encompasses most dry grasslands dominated by typical grasses such as Chrysopogon gryllus, Festuca valesiaca, and Bromopsis erecta, although local facies can be dominated also by other species [19]. The three main clusters within this association are distinguished at the subassociation level. The typical subassociation, including relevés mostly assigned to the Asphodelo-Chrysopogonetum grylli by Horvatić [19], is characterized by Cytisus spinescens and Asphodelus ramosus and is restricted to Pag Island in the Kvarner area, Croatia. The bioclimate here is temperate oceanic, with a (strongly to highly strongly) sub-Mediterranean variant, a mesotemperate thermotype, and a (upper) subhumid to (lower) humid ombrotype. The other two clusters are united under the subassociation Bromopsido erectae-Chrysopogonetum grylli piloselletosum officinarum subass. nov., which includes relevés predominantly previously classified under the Festuco-Koelerietum splendentis. Since the new subassociation includes the nomenclatural type of the Festuco-Koelerietum splendentis, this association is de facto lowered to the rank of subassociation, thereby retaining its type relevé and original diagnosis (synoptic table on page 74 in [19]). The Bromopsido erectae-Chrysopogonetum grylli piloselletosum officinarum occurs under varying bioclimatic conditions, primarily within the sub-Mediterranean oceanic temperate bioclimate, with only a few relevés falling within the pluvio-seasonal Mediterranean bioclimate. It is characterized by species such as Sedum sexangulare, Pilosella officinarum, Linum tenuifolium, Festuca stricta subsp. sulcata (i.e., Festuca illyrica), Fumana procumbens, Euphorbia spinosa, Lotus corniculatus, Euphorbia cyparissias, and Centaurea tommasinii. Trinajstić [21,35] described several subassociations of the Festuco-Koelerietum splendentis, but our results do not support such a formalized variability. Further data and analyses are likely needed to investigate the diversity of this association across its broad distribution range, possibly extending to Albania, where it has been recorded along the Buna River [42]. In this area, however, the floristic composition is slightly different from that recorded to the north (see Supplement S6).

• Bromo erecti-Chrysopogonetum grylli sensu Stanišić-Vujačić et al., 2022 (“BCs”) [=Sideritido purpureae-Asphodeletum ramosi ass. nov.].

Dominant taxa: Asphodelus ramosus (46.8), Chrysopogon gryllus (12.1), Sanguisorba minor (11.7), Anemone hortensis (6.2), Centaurea deusta (6.1), Poa bulbosa (5.8), Teucrium capitatum subsp. capitatum (5.1).

Diagnostic taxa: Sideritis romana subsp. purpurea, Centaurea deusta, Daucus guttatus, Allium guttatum subsp. sardoum.

Constant taxa: Asphodelus ramosus (100), Poa bulbosa (100), Sanguisorba minor (100), Sideritis romana subsp. purpurea (100), Teucrium capitatum subsp. capitatum (100), Anacamptis papilionacea (94.1), Chrysopogon gryllus (88.2), Cynodon dactylon (88.2), Eryngium amethystinum (88.2), Helianthemum salicifolium (88.2), Hypericum perforatum (88.2), Crepis sancta subsp. sancta (82.4), Geranium columbinum (82.4), Centaurea deusta (76.5), Euphorbia exigua (76.5), Hippocrepis ciliata (76.5), Anemone hortensis (70.6), Anthoxanthum odoratum (70.6), Crupina vulgaris (70.6), Daucus guttatus (70.6), Koeleria splendens (70.6), Allium guttatum subsp. sardoum (64.7), Asterolinon linum-stellatum (64.7), Avena barbata (64.7), Cerastium pumilum subsp. glutinosum (64.7), Leontodon crispus (64.7), Scolymus hispanicus (64.7).

Description: Although the relevés of this association collected in Ćemovsko polje, Montenegro, were originally classified as Bromo erecti-Chrysopogonetum grylli [44], they exhibit significant differences than those found in Croatia, and Bosnia and Herzegovina. Among all the associations within the Chrysopogono grylli-Koelerion splendentis, these therophytic stands demonstrate the highest level of disturbance and continentality, despite their exposure to Mediterranean influences. Specifically, this plant community thrives in the sub-Mediterranean variant of the continental temperate bioclimate, characterized by a mesotemperate thermotype and a (lower) humid ombrotype. In contrast to the Bromo erecti-Chrysopogonetum grylli, which typically occurs on outcropping limestones with thin soils, the plant community in Ćemovsko polje is found on deeper alluvial soils [44]. The latter is floristically distinct from other associations due to a significant number of annual species belonging to the classes Stipo-Trachynetea and Tuberarietea guttatae. Indeed, indicator species associated with this cluster (Supplementary S6) include many annuals. This plant community is dominated by Asphodelus ramosus and Chrysopogon gryllus, yet it lacks species typically found in dry grasslands of the alliance Chrysopogono grylli-Koelerion splendentis, such as Salvia officinalis and Bromopsis erecta. Given its unique environmental conditions and floristic composition, this community is recognized as an autonomous association: Sideritido purpureae-Asphodeletum ramosi ass. nov.

Biondi et al. ([86,87], see also [44,47,88]) proposed the classification of the associations dominated by Asphodelus ramosus (such as the Sideritido purpureae-Asphodeletum ramosi and the Narcisso tazettae-Asphodeletum microcarpi), within a newly established alliance and class. However, the proposal to amend the EVC by incorporating this new class (Charybdido pancratii-Asphodeletea ramosi) was rejected, as the floristic boundaries between the proposed class and neighboring classes had not been sufficiently delineated [89]. Consequently, in this study, we adhere to the syntaxonomic framework currently recognized in the EVC.

• Narcisso tazettae-Asphodeletum microcarpi (“NA” in Figure 2).

Dominant taxa: Narcissus tazetta (29.4), Asphodelus ramosus (24.5), Helichrysum italicum (8.9), Brachypodium retusum (8.7), Bromopsis erecta (5).

Diagnostic taxa: Narcissus tazetta.

Constant taxa: Asphodelus ramosus (100), Narcissus tazetta (100), Helichrysum italicum (82.6), Reichardia picroides (78.3), Catapodium rigidum (73.9), Dactylis glomerata subsp. hispanica (73.9), Plantago lanceolata (73.9), Bothriochloa ischaemum (65.2), Bellis sylvestris (60.9), Brachypodium retusum (60.9), Bromopsis erecta (60.9), Cynosurus echinatus (60.9).

Description: This well-defined association was first described for Istria (Croatia) [22,23] and has since been reported from several Croatian islands [32,43,45] (Supplementary S1). In its locus classicus in Istria, this association no longer exists, having been replaced by buildings or degraded due to anthropogenic disturbances. The Narcisso tazettae-Asphodeletum microcarpi primarily occurs on deeper skeletoid soils under the influence of salt spray [23]. Hećimović [32] invalidly (Art. 5a) described the subassociation Narcisso tazettae-Asphodeletum microcarpi sisymbrietosum officinalis on the islands of Bobara and Mrkan in southern Croatia. This subassociation is distinguished by a significant proportion of nitrophilous species from the classes Sisymbrietea and Chenopodietea, possibly due to the influence of bird activity. Since Asphodelus microcarpus Viv. is replaced in several floras in current use (e.g., [55,63]) by Asphodelus ramosus L., the name Narcisso tazettae-Asphodeletum microcarpi Šegulja 1969 [23] (p. 368) is here mutated (Art. 45) with the alternative form Narcisso tazettae-Asphodeletum ramosi. The Narcisso tazettae-Asphodeletum ramosi sisymbrietosum officinalis is here validated by selecting rel. 4, Table 5 in Hećimović [32] as the holotype. The sole character species of this association is Narcissus tazetta, which, along with Asphodelus ramosus, serves as the main dominant species.

Herein is presented the syntaxonomic scheme with names corrected according to the ICPN (Supplementary S8). After the syntaxon names, the nomenclatural type relevé and the location where it was sampled are reported. In parentheses are the corresponding names.

Class: Festuco-Brometea Br.-Bl. et Tx. ex Soó 1947.

Order: Scorzoneretalia villosae Kovačević 1959.

Alliance:Chrysopogono grylli-Koelerion splendentis Horvatić 1973.

Brachypodio retusi-Salvietum officinalis Terzi, Jasprica, Pandža, Milović et Caković 2023. Holotypus: rel. in Appendix A, in [46], i.e., rel. 81 of the Supplementary Table 2, in [46], recorded in the Kornat Island, Kornati Archipelago, Croatia.

Stipo-Salvietum officinalis Horvatić 1963. Neotypus [13]: rel. 1, Table 2, in [33], Unije Island, Croatia.

• • typicum.
  • campanuletosum lingulatae Terzi, Jasprica, Pandža, Milović et Caković 2023. Holotypus rel. in Appendix A in [46], Virpazar, Montenegro.

Festuca dalmatica-Brachypodium retusum plant community (= Koelerio splendentis-Festucetum illyricae brachypodietousm retusi sensu Kamenjarin and Pavletić 2003).

Centaureo cristatae-Chrysopogonetum grylli Ferlan et Giacomini 1957 nom. invers. Lectotypus [13]: rel. 70, Table 1 in [16], Doberdò del Lago, Gorizia, Italy.

• • typicum.
  • genistetosum sericeae Poldini (1980) 1989. Holotypus: rel. 2, Table 14, page 105, in [30], Aurisina, Trieste, Italy (Corresponding name: Seseli gouanii-Artemisietum albae Poldini 1980).
  • rhamnetosum intermediae (Horvat in Horvat, Glavač et Ellenberg 1974) Terzi, Jasprica et Pesaresi subass. nov. (Corresponding name: Saturejo montanae-Ischaemetum Horvat in Horvat, Glavač et Ellenberg 1974; Neotypus rel. 34 in Supplementary S3 and Appendix A, Kukuljanovo, near Rijeka, Croatia).

Salvio officinalis-Euphorbietum fragiferae Lausi et Poldini 1962 Lectotypus [13]: rel. 17, Table 3, in [17], Trieste (along the road from Venice to Trieste), Italy.

Lactuco vimineae-Ischaemetum Poldini 1975. Lectotypus [13]: rel. 11, tab. I in [28].

• • typicum.
  • helichrysetosum italici (Trinajstić ex Poldini 1975) Terzi, Jasprica et Pesaresi subass. nov. (Corresponding name: Dichanthio ischaemum-Cleistogenetum serotinae Trinajstić ex Poldini 1975; Neotypus hoc loco: rel. n. 13 in Supplementary S3 and Appendix A).

Armerio dalmaticae-Helichrysetum italici Horvatić 1963 nom. invers. Neotypus hoc loco: rel. 23 in Supplementary S3 and Appendix A, Pag Island, Croatia.

Salvio officinalis-Seslerietum juncifoliae Trinajstić 1977 Lectotypus [13]: rel. 5, Table V, in [29], Hvar Island, Croatia.

Bromopsido erectae-Festucetum lapidosae Trinajstić 1992 mut. Terzi, Jasprica et Pesaresi nom. mut. nov. Holotypus: rel. 4, Table 2 in [35], Brač Island, Croatia.

Brachypodio retusi-Koelerietum macranthae Trinajstić 2005 nom. invers. Holotypus: rel. 1, Table 1, page 351, in [39]; Dubrovnik, Croatia.

Helichrysetum italici Horvatić 1927. Neotypus [47]: rel. 3, Table 2, page 125 in [47], Plavnik Island, Croatia.

• • typicum.
  • salvietosum officinalis Terzi and Jasprica 2024 Holoypus: rel. 13, Table 2, page 125 in [47]; Plavnik Island, Croatia.

Festucetum valesiaco-illyricae Horvat in Horvat, Glavač et Ellenberg 1974 corr. Trinajstić 2000 nom. invers. Neotypus [36]: rel. 5, Table 1, page 252, in [36]; Um hill in Gacko polje, Lika, Croatia.

Bromopsido erectae-Chrysopogonetum grylli Horvatić 1934 mut. Terzi, Jasprica et Pesaresi nom. mut. nov. Lectotypus [13]: rel. 17, Table XXVIII, in [14]; Pag Island, Croatia

• • typicum.
  • piloselletosum officinarum (Horvatić 1963) Terzi, Jasprica et Pesaresi subass. nov. (Corresponding name: Festuco-Koelerietum splendentis Horvatić 1963; Neotypus [35]: rel. 7, Table 1, in [35]; Područje Pođi, Vrpolje, Šibenik, Croatia).

Sideritido purpureae-Asphodeletum ramosi ass. nov. Holotypus: rel. 14, Table 1, p. 15 in [44], Ćemovsko polje, Montenegro.

Narcisso tazettae-Asphodeletum ramosi Šegulja 1969 mut. Terzi, Jasprica et Pesaresi nom. mut. nov. Neotypus [13]: rel. 1, Table 2, in [24], Sveta Marina, Istria, Croatia.

• • typicum.
  • sisymbrietosum officinalis Hećimović ex Terzi, Jasprica et Pesaresi subass. nov. Holotypus: rel. 4, Table 5 in [32], Bobara Island, Croatia.

Festuco-Linetum flavi Ritter-Studnička 1972. Only a synoptic table is currently available, from Glamočko polje and Livanjsko polje, Bosnia and Herzegovina.

5. Conclusions

The Chrysopogono grylli-Koelerion splendentis represents a significant component of the landscape in western Balkans, both in terms of spatial extent and functional importance. Despite the presence of numerous facies, characterized by the dominance of different species, the coenological diversity can be summarized into 15 associations, some of which are restricted to specific islands or archipelagos. The findings of this study also highlight the need for new phytosociological data from the southernmost distribution areas of the alliance (Albania, Montenegro), as well as from inland regions (Bosnia and Herzegovina, North Macedonia), where differentiated vegetation assemblages are likely present but remain poorly documented. Indeed, understanding coenological variability is crucial not only for enhancing our knowledge of syntaxonomic diversity but also for the effective monitoring and management of the biodiversity contained within these ecosystems.