Taxonomy and Distribution of Spiraea hypericifolia in Italy and Typification of the Name S. flabellata (Rosaceae)

Spiraea hypericifolia is a Eurasiatic species, distributed from SW Europe to C and SW Asia. In Italy, only the alien S. hypericifolia subsp. obovata was recorded, as naturalized in the Central Apennines. Spiraea flabellata was described from Abruzzo (Central Apennines, Italy) by Gussone in 1826 and is currently regarded as a synonym of S. hypericifolia subsp. obovata. Based on the study of living plants from locus classicus and the analysis of the original material traced in BOLO and NAP, S. flabellata should be referred instead to S. hypericifolia subsp. hypericifolia, a taxon reported here for the first time in Italy. The name S. flabellata is lectotypified with a specimen kept in NAP. Based on our study, S. hypericifolia subsp. obovata should be excluded from Italian flora. Spiraea hypericifolia subsp. hypericifolia should be considered native to Italy and added to the contingent of steppe plants of phytogeographic and conservation interest recorded in the Central Apennines. Finally, the conservation status assessment of S. hypericifolia subsp. hypericifolia according to IUCN categories and criteria, is proposed and discussed.


Introduction
As part of the research on the flora of the Abruzzo, Lazio, and Molise National Park [1-3], we have studied some critical species groups from a systematic and taxonomic point of view [4][5][6][7]. One of these is Spiraea hypericifolia L., a Eurasiatic species with a native range from SW Europe to C and SW Asia. Within S. hypericifolia two subspecies are currently recognized in Europe [8]: subsp. hypericifolia occurring from SE Europe, Turkey to Siberia, West and Central Himalaya, introduced to Belarus, and subsp. obovata (Waldst. & Kit. ex Willd.) H.Huber native in France and Spain, introduced to Belgium and doubtful in Italy and Morocco [9].
The aim of the present work is to clarify the taxonomic identity of S. flabellata and to review the taxonomy and distribution of S. hypericifolia in Italy.

Materials and Methods
This study is based mainly on field surveys, on an extensive analysis of the relevant literature, and on careful examination of herbarium specimens (including the original Plants 2023, 12, 536 2 of 9 material), kept in APP, AUR, BM, BOLO, H, LINN, LY, NAP, NIM, and TALL (codes follow Thiers [20]).
In order to investigate the morphological variability of Spiraea hypericifolia, 87 dried individuals belonging to S. hypericifolia subsp. hypericifolia (59) and subsp. obovata (24) were studied. According to Dostál [8], the diagnostic characters to identify the two taxa are the shape of leaves, the shape and length of petals in relation to the stamens, and the ratio between the length of sepals and the hypanthium. We measured the characters proposed by Dostál (Table 1) except for the shape and length of petals in relation to stamens. Based on our preliminary observations, these characters are difficult to observe on the herbarium specimens and do not seem to discriminate the infraspecific taxa. The variability of the analyzed morphological characters was described by standard statistical parameters (minimum, maximum, 10 th, and 90 th percentiles). All morphological characters of herbarium specimens were observed and measured under a Leica MZ16 stereoscopic microscope, using a digital caliper with 0.1 mm precision. The digital images of herbarium specimens were measured with IC Measure version 2.0.0.245.
The lectotype designation herein follows the Shenzhen Code ( [21], hereafter ICN).  Figure 1). Spiraea flabellata was first described by Gussone [10] from Abruzzo (Central Italy), who provided a detailed description, quoting a precise collection locality and citing an illustration "Ic. nostra t. 40". We were able to trace some herbarium specimens housed in BOLO and NAP, which can be considered original material (Art. 9.4 of the ICN), as well as the illustration "t. 40" cited in the protologue ( Figure 2). In BOLO, we traced one specimen collected by Gussone "Colline presso Aquila a S. Demetrio, misit Gussone 1826". In the Gussone Herbarium in NAP, we traced four specimens, collected by Gussone: "S. Demetrio presso Aquila, Agosto 1823" (barcode NAP0000370), "S. Demetrio pr. Aquila (barcodes NAP0000371, NAP0000372), "nella Marsica presso il Lago di Fucino a Trasacco, Agosto 1823" (barcode NAP0000373). The herbarium specimen barcoded NAP0000370 is complete, well conserved, agrees with the protologue, and is selected here as lectotype for the name S. flabellata.   Distribution: in Italy, it is currently present only in Abruzzo in the Fucino plain and in the L'Aquila basin (Figure 3). Its presence in Umbria was based on old bibliographic references [15,[17][18][19] from hills near Spoleto, and not recently confirmed. We were able to trace an old herbarium specimen housed in BOLO collected from Spoleto (see Specimens examined).
Plants 2022, 11, x FOR PEER REVIEW 5 of 9 Distribution: in Italy, it is currently present only in Abruzzo in the Fucino plain and in the L'Aquila basin (Figure 3). Its presence in Umbria was based on old bibliographic references [15,[17][18][19] from hills near Spoleto, and not recently confirmed. We were able to trace an old herbarium specimen housed in BOLO collected from Spoleto (see Specimens examined). Phenology: flowering from late April to May; fruiting in June and July. Habitat and ecology: bushes, hedges in arid hemicryptophytic grasslands at an elevation of 670-900 m a.s.l. We have studied some populations of S. hypericifolia in the field of Abruzzo "continental valleys" (including the locus classicus of S. flabellata), specifically, in the Fucino plain, near Trasacco and Collelongo, and in the L'Aquila basin between Barisciano and San Demetrio ne' Vestini ( Figure 4). In the latter locality, we were able to confirm the presence of S. hypericifolia, where the species was known on the basis of an old report by Gussone [10] and never confirmed again. In the investigated populations, S. hypericifolia often forms bushes that are monophytic or accompanied by Prunus spinosa L. subsp. spinosa, Crataegus monogyna Jacq., Rosa subcollina (Christ) Vuk., and, more rarely, by Prunus dulcis (Mill.) D.A.Webb, surrounded by steppe grasslands. In the Fucino plain, S. hypericifolia grows in the fluvio-glacial valley of the Rosa torrent between Trasacco and Villavallelonga, on the edge of arid hemicryptophytic grasslands, rich in steppe relict elements, locally dominated by Stipa capillata L. and Festuca valesiaca Schleich. ex Gaudin subsp. valesiaca, and near Trasacco and Ortucchio. These steppe grasslands have recently been attributed to the priority habitat of EU Habitats Directive "6240 Sub-pannonic steppic grasslands" [22]. The population between Barisciano and S. Demetrio ne' Vestini, grows in the L'Aquila basin with a marked continental character similar to the Fucino basin, where dominate dry grasslands with Stipa capillata and S. dasyvaginata Martinovský subsp. apenninicola Martinovský & Moraldo. Phenology: flowering from late April to May; fruiting in June and July. Habitat and ecology: bushes, hedges in arid hemicryptophytic grasslands at an elevation of 670-900 m a.s.l. We have studied some populations of S. hypericifolia in the field of Abruzzo "continental valleys" (including the locus classicus of S. flabellata), specifically, in the Fucino plain, near Trasacco and Collelongo, and in the L'Aquila basin between Barisciano and San Demetrio ne' Vestini ( Figure 4). In the latter locality, we were able to confirm the presence of S. hypericifolia, where the species was known on the basis of an old report by Gussone [10] and never confirmed again. In the investigated populations, S. hypericifolia often forms bushes that are monophytic or accompanied by Prunus spinosa L. subsp. spinosa, Crataegus monogyna Jacq., Rosa subcollina (Christ) Vuk., and, more rarely, by Prunus dulcis (Mill.) D.A.Webb, surrounded by steppe grasslands. In the Fucino plain, S. hypericifolia grows in the fluvio-glacial valley of the Rosa torrent between Trasacco and Villavallelonga, on the edge of arid hemicryptophytic grasslands, rich in steppe relict elements, locally dominated by Stipa capillata L. and Festuca valesiaca Schleich. ex Gaudin subsp. valesiaca, and near Trasacco and Ortucchio. These steppe grasslands have recently been attributed to the priority habitat of EU Habitats Directive "6240 Sub-pannonic steppic grasslands" [22]. The population between Barisciano and S. Demetrio ne' Vestini, grows in the L'Aquila basin with a marked continental character similar to the Fucino basin, where dominate dry grasslands with Stipa capillata and S. dasyvaginata Martinovský subsp. apenninicola Martinovský & Moraldo.  Conservation status: Spiraea hypericifolia currently occurs in Central Apennines in Abruzzo, in the L'Aquila basin, and in the Fucino plain. In the latter locality, the population is partly inside the NATURA 2000 network within the SAC IT7110205 "Parco Nazionale d'Abruzzo". The population in Umbria (Central Italy), confirmed by one old herbarium specimen, has not been observed for over 180 years. The Extent of Occurrence (EOO) is 231.104 km 2 , and the area of occupancy (AOO) is 24 km 2 (cell 2×2 km) calculated with GeoCAT (Geospatial Conservation Assessment Tool) software [23]. The species is present in two locations (six subpopulations), and a decline in the EOO and AOO was inferred, considering the possible extinction of the population in Umbria. A decline of the quality of habitat, due to the presence of the invasive alien Ailanthus altissima (Mill.) Swingle, was observed. According to IUCN [24] criterion B2ab(i,ii,iii,iv), the species is assessed as Endangered (EN) at the regional level (Italy).
Taxonomic notes: based on studied and measured herbarium material, S. hypericifolia subsp. hypericifolia (including S. flabellata) showed narrower leaves than in subsp. obovata and hypanthium clearly longer than sepals (see Table 1).  Conservation status: Spiraea hypericifolia currently occurs in Central Apennines in Abruzzo, in the L'Aquila basin, and in the Fucino plain. In the latter locality, the population is partly inside the NATURA 2000 network within the SAC IT7110205 "Parco Nazionale d'Abruzzo". The population in Umbria (Central Italy), confirmed by one old herbarium specimen, has not been observed for over 180 years. The Extent of Occurrence (EOO) is 231.104 km 2 , and the area of occupancy (AOO) is 24 km 2 (cell 2 × 2 km) calculated with GeoCAT (Geospatial Conservation Assessment Tool) software [23]. The species is present in two locations (six subpopulations), and a decline in the EOO and AOO was inferred, considering the possible extinction of the population in Umbria. A decline of the quality of habitat, due to the presence of the invasive alien Ailanthus altissima (Mill.) Swingle, was observed. According to IUCN [24] criterion B2ab(i,ii,iii,iv), the species is assessed as Endangered (EN) at the regional level (Italy).
Taxonomic notes: based on studied and measured herbarium material, S. hypericifolia subsp. hypericifolia (including S. flabellata) showed narrower leaves than in subsp. obovata and hypanthium clearly longer than sepals (see Table 1