The Genus Sagina (Caryophyllaceae) in Italy: Nomenclatural Remarks

A contribution to the nomenclature of the genus Sagina is presented. The following 10 taxa are recognized as being part of the Italian flora: S. alexandrae, S. apetala, S. glabra, S. maritima, S. micropetala, S. nodosa, S. pilifera, S. procumbens, S. revelierei, and S. saginoides subsp. saginoides. The names S. apetala var. decumbens (=S. apetala subsp. apetala), S. bryoides (=S. procumbens), S. patula (=S. apetala subsp. apetala), S. revelierei, Spergula glabra (=S. glabra), Spergula pilifera (=S. pilifera), and Spergella subulata var. macrocarpa (=S. saginoides subsp. saginoides) are here typified. Specimens deposited at B-W, C, E, and LY, and illustrations by Reichenbach were considered for the typifications. Specifically, two Reichenbach’s illustrations are chosen for S. bryoides and S. saginoides var. macrocarpa. A specimen at B-W is designated as the lectotype of S. glabra. Two specimens at C and G are designated as the lectotypes of S. apetala var. decumbens and S. revelierei, respectively. A specimen at LY is designated for S. patula. As we did not find original material, a neotype at G is designated for S. pilifera.


Introduction
Sagina L. (Sagineae J.Presl, Caryophyllaceae Juss.) is a genus of about 30 species mostly occurring in the North-temperate and arctic regions (center of diversity in Europe), while a few taxa can be found in tropical mountains [1].Species of Sagina are small, erect, or procumbent (sometimes caespitose or cushion forming), as well as annual or perennial herbs; most species have white petals.A detailed comprehensive monography of the whole genus is still lacking, but molecular data demonstrated that Sagina is monophyletic [2,3].
As part of ongoing studies of Italian Caryophyllaceae [5][6][7][8][9][10][11][12][13][14][15], in this study, we present a contribution to the knowledge of Sagina in Italy by answering open nomenclatural questions and being preliminary to the taxonomic revision of the genus at the national level.

Results and Discussion
2.1.Publication and Typification of Names 2.1.1.Sagina apetala var.decumbens Hornemann [16] (p. 3) proposed two varieties of Sagina apetala, i.e., S. apetala var.erecta and S. apetala var.decumbens, and associated them with an illustration ("Table MMCII", available at http://bibdigital.rjb.csic.es/ing/Libro.php?Libro=4640&Pagina=160, accessed on 24 August 2023 This illustration represents two complete plants (one placed on the top of the plate and the other placed at the center of the plate), as well as a series of eight detailed drawings (lower part of the plate), showing the particulars of leaves, gynoecium and androecium, a first fruit with adpressed sepals, a second fruit with patent sepals, and a seed.According to the protologue by Hornemann (1834: 3), the upper plant drawing illustrates S. apetala var.erecta ("Fig.
[=Figura] superior var.erecta"), whereas the complete figure corresponds to S. apetala var.decumbens ("Fig. [=Figura] infer.var.decumbens").Although no diagnosis was provided for the two varieties, the names can be considered as validly published based onto Art.38.9 of the ICN.
Dillenberger and Kadereit [17] (p.20) lectotypified the name Sagina apetala var.erecta using a specimen deposited at C (C10024083), whereas no definitive conclusion was given for S. apetala var.decumbens.These authors [17] stated that the "protologue [of S. apetala varieties by Hornemann] does not provide separate information for S. apetala var.erecta and var.decumbens.Specimen No. 3 on the sheet consists of three large plants all belonging to S. micropetala and has the correct location, collector and date.Specimen No. 1 seems to include S. apetala var.decumbens, No. 2 lacks a date, and label information of No. 4 does not fit the protologue".Furthermore, in the text, Dillenberger and Kadereit [17] (p.15) reported in the text that: "The growth form of var.decumbens clearly excludes it from S. apetala and S. micropetala so that var.decumbens most likely represents S. procumbens".Therefore, as a whole, the authors [17] had doubts about the identification of Hornemann's S. apetala var.decumbens.We carefully checked both C10024083 [17] (p.19, Figure 2) and the treatment of Sagina by Hornemann [p. 3 and Tables MMCII (Sagina apetala), MMCIII (Sagina procumbens L.), and MMCIV (Sagina maritima)] [18].Specimen No. 1 in C10024083 consists of three complete plants (with roots, leaves, sepals, and fruits) and it is associated with the following label (bottom-right corner of the sheet): "1|Sagina apetala L. var.depressa Schultz|... bei Ratzeburg | leg.Nolte".Two of these three plants (the first plants on the left) of specimen No. 1 in C10024083 are clearly prostrate and, therefore, match Hormenan's concept of S. apetala var.decumbens [16] (Table MMCII-central illustration).Although the year of collection is not specified on this label, the collector and the locality are compatible with the protologue, as Ratzeburg is the capital of the district Herzogtum Lauenburg (Lower Saxony, Germany).Therefore, it is very likely that the Danish botanist used these plants to describe S. apetala var.decumbens, as well as using the plants of specimen No. 3 to describe S. apetala var.erecta [17].Thus, we designate this latter as the lectotype of Sagina apetala var.decumbens.
Concerning the identity of Sagina apetala var.decumbens, we firstly noted that most of the authors cited by [17] (p. 3) in synonymy [18][19][20][21][22] referred to the taxon currently known as S. apetala subsp.apetala (excluding Nolte and Weber [23] (p.119), who treated Sagina maritima Don).On the other hand, as mentioned above, Dillenberger and Kadereit [17] (p.15) supposed that Hornemann's S. apetala var.decumbens could be S. procumbens.This latter species is the only perennial Sagina member among those species with tetramerous flowers (see, e.g., [17,24]).Both the lectotype chosen and the illustrations by Hornemann [16] (Table XXCII) clearly show annual plants.The detailed drawing at the bottom of the plate (the second one from the right) that shows fruits with patent and obtuse sepals is referred to as S. apetala var.erecta (=S.micropetala, according to [17]).The other fruit drawn, which is subtended by adpressed and acute sepals (the third drawing from the right on the bottom of Table MMCII), clearly is S. apetala var.decumbens (=var.apetala).

Sagina bryoides
Reichenbach [25] (p.793) published the name Sagina bryoides, providing a diagnosis and provenance ("Tyrol, im Bassin Lyn bei Steeg"), gathering details ("Frölich [Froelich]", "31 Aug. 1811"), and citing an illustration of his own [25]: "Rchb.pl.crit.XI. ic. . ..". Evidently, this illustration, as well as that of the subsequent Sagina ciliata Fr. [25], was planned to be published within the 19th centuria in Iconographia botanica seu plantae criticae.However, as clarified by Stafleu and Cowan [26], the series stopped after the 10th volume in either 1832 or 1834, and the remaining centuries of plates were incorporated into the first volumes of Icones florae germanicae et helveticae.In particular, the first volume would count as being published in the century of Iconographia botanica, but it is entirely devoted to monocots and, therefore, titled "Agrostographia germanica" [26].The illustration of interest was only published in 1841 or 1842 within the fifth volume of Icones florae germanicae et helveticae, namely as the No. 4955 of the plate CC [27].We do not know if the plate had previously been realized when Reichenbach published the protologue [25]; therefore, even if this is possible, to the best of our knowledge, it cannot be considered as original material.Nevertheless, the syntype cited by Reichenbach [25], i.e., a specimen collected by Froelich on 31 August 1811 in Tyrol, as well as any further specimen linked to Reichenbach, was not traced.According to Stafleu and Cowan [28] (p.893), the hosting place of Froelich's Herbarium is unknown.Therefore, the illustration cited by Reichenbach [25], albeit published only nine years later, remains the only known material definitively linked to him, and future studies might consider it to be original material.Therefore, we prefer to designate it as the neotype of the name Sagina bryoides.On the basis of the current concept in Sagina (see e.g., [24]), S. bryoides, and the chosen neotype, it can be referred to S. procumbens.

Sagina revelierei
Jordan and Fourreau [29] (p.11) published the name Sagina revelierei (as "revelieri") to honor the first collector Eugène Revelière; this name does not have a well-established Latin form and, therefore, must corrected according to Arts.60.1 and 60.8 (a) of the ICN.Jordan and Fourreau [29] provided a detailed diagnosis and the provenance ("Hab. in montibus Corsicae: Quenza, ex dom.E. Revelière"); they also provided a morphological comparison between S. linnaei C.Presl and S. subulata, taking the work of Presl into account [30] (p.14), which listed the valid Spergula saginoides L. as a synonym of S. linnaei.As a consequence, S. linnaei is a superfluous and illegitimate name under the Arts.52.1 and 52.2 of the ICN.
Following Stafleu and Cowan [26] (p.746), we searched Revelière's specimens and traced two sheets at LY [LY0826457 and LY0826458 (at https://explore.recolnat.org/occurrence/989AB9E6EAB340EFA3629CD7DB0C398C, accessed 19 July 2023)].These specimens were collected by Reveliére in 1863 at Quenza, and Jordan in 1865 at the Garden of Villeurbanne (plants grown from seedling cultivated in 1864 and coming from Quenza), respectively.Both specimens, which can be considered to be part of the original material for the name Sagina revelierei, morphologically match the protologue and the current concept of the species [24].We designate the specimen LY0826457, which was directly collected by Reveliére, as the lectotype of Sagina revelierei.
Between the two elements suitable for the typification of the name Spergula glabra, we decide to designate the specimen at B as the lectotype, since it is a better choice regarding the illustrations [32] (pp.21−22).

Spergula pilifera
Lamarck and Candolle [33] (p.774) provided a detailed diagnosis of the name Spergula pilifera, using data about its provenance and collectors ("Elle croît sur les hautes montagnes de l'isle de Corse, d'où M. Robert en a envoyé des échantillons que je décris dans l'herbier de M. Clarion" = it grows on the high mountains of the island of Corsica, where Mr. Robert sent samples of it, which are described in Mr. Clarion's herbarium); this latter citation is a sintype according to Art. 9.6 of the ICN.
According to Stafleu and Cowan [28] (p.506), Clarion's collection is preserved at P-JU (Jussieu Herbarium).Unfortunately, among the 17 specimens preserved at P (see https://science.mnhn.fr/institution/mnhn/collection/p/item/list?scientificName= Spergula+pilifera, accessed on 10 August 2023), none are part of the original material (it was either not collected by Clarion or not noted before 1805).Also, C. Aupic (pers.comm.)confirmed that no Clarion's specimen of Sagina pilifera is deposited at P. As a consequence, a neotypification is required by the Art.9.8 of the ICN.We traced a specimen at G (G00212132), which is represented by one plant collected by Robert in 1808 in Corsica.This exsiccatum is, therefore, a good candidate to be a neotype for the name Spergula pilifera, as it morphologically corresponds both to the protologue and to the current concept of Sagina pilifera [26].

Conspectus of the Genus Sagina in Italy
We here present a nomenclatural conspectus of the following 10 Sagina taxa occurring in Italy: Note: POWO [36] reported that Sagina alexandrae is a synonym of S. hawaiesis Pax.However, the question arising from the synonymization of these two names is quite complicated, and Iamonico and Dillenberger (in prep.) are studying it from both nomenclatural and molecular points of view.Note: Crow [35] (p.34) and Tropicos [42] report that Beck's combination is illegitimate.However, the name was correctly proposed by Beck (Art.55.2 of the ICN).

Material and Methods
The present study was carried out through an extensive literature analysis and the examination of specimens kept at B, BM, C, E, G, K, L, LE, LY, MPU, NAP, P, PH, RO, TO, and UPS (herbarium codes were determined according to the Index Herbariorum [43]).The articles cited through the text follow the Shenzhen Code (hereafter "ICN") [42].Besides the accepted names and their basionyms, all of the homotypic synonyms were examined, and the most frequent heterotypic names.

Conclusions
On the basis of a detailed study of both the protologues and the original material regarding several names of Sagina and Spergula, we are able to clarify their identities via the designation of neo-or lectotypes.Most of these names are confirmed to be heterotypic synonyms.Concerning the homotypic synonyms, we noted that many genera were considered to identify the various taxa, e.g., Alsine L. (currently Stellaria L.), Moehringia L. (currently accepted), Phaloe Dumort.(currently Sagina), Spergella Rchb.(currently Sagina), Spergula L. (currently accepted), etc.Also, the various taxa were originally described or recombined during the time at all ranks, ranging from species to subcategories (subspecies, variety, and form).This proliferation of names and taxa reveals the high phenotypic variability in the genus Sagina, on one hand, as well as the confusion in their attribution to both the genus and the correct rank, on the other hand.The nomenclatural study here presented thus shows the importance of nomenclature in Systematic Botany, as it provides a base for future taxonomic investigations.