A conspectus of the genus Cherleria (Minuartia s.l., Caryophyllaceae)

Abstract: 
 Minuartia s.l. (Caryophyllaceae) is polyphyletic, with its species belonging to eleven major clades, all of which have been recognized at the generic rank. Cherleria is one of these segregate genera, based on the Linnaean species Cherleria sedoides. Its centre of diversity is on the Balkan Peninsula, but species also occur in the European and North American high mountains and in the Arctic. The species of Cherleria show ecological, especially substrate, differentiation and multiple colonisations of alpine habitats. We make new combinations for the 17 (of 20) taxa in Cherleria that do not yet have Cherleria names and provide a key to all species of the genus. Citation: Moore A. J. & Dillenberger M. S. 2017: A conspectus of the genus Cherleria (Minuartia s.l., Caryophyllaceae). — Willdenowia 47: 5–14. doi: https://doi.org/10.3372/wi.47.47101 Version of record first published online on 09 February 2017 ahead of inclusion in April 2017 issue.


Introduction
The genus Minuartia L. (Caryophyllaceae) had been defined by having three styles and three capsule teeth (Mattfeld 1922;McNeill 1962). Molecular studies have shown this circumscription of Minuartia to be highly polyphyletic (Fior & al. 2006;Harbaugh & al. 2010;Greenberg & Donoghue 2011;Dillenberger & Kadereit 2014). For this reason, Dillenberger & Kadereit (2014) broke Minuartia up into 11 different genera, based on their analyses of cpDNA and nrDNA sequence data and on having clades that were morphologically distinctive. Although they made new combinations for most species of Minuartia, no combinations were made for one of the segregate genera, Cherleria L., their Clade 6, because of ongoing work on the circumscription of its species. We present the results of that study here.
Cherleria is clearly supported with 100 percent bootstrap in the combined cpDNA and nrDNA tree and is the sister to the genus Scleranthus L. (Dillenberger & Kadereit 2014). It is one of two groups of Minuartia s.l. whose sepals have obtuse, rounded tips, instead of acute tips, a characteristic shared with its sister group Scleranthus. The other group of Minuartia s.l. with rounded sepal tips is Dillenberger & Kadereit's (2014) Clade 3, which they named Pseudocherleria Dillenb. & Kadereit. The two groups are separated by the presence of glandular or single-celled non-glandular hairs in Cherleria (versus multicellular, non-glandular hairs in Pseudocherleria) and by the leaves generally being linear-setaceous to subulate in Cherleria (versus lanceolate in Pseudocherleria; Dillenberger & Kadereit 2014). In the most recent monograph of Minuartia as a whole, Mattfeld (1922)  The only member of Cherleria as here circumscribed that Mattfeld (1922) did not include in Minuartia sect. Spectabiles is C. sedoides L. itself, which he placed in the unispecific M. sect. Cherleria (L.) Mattf. Although Mattfeld (1922) considered M. sect. Cherleria to be only distantly related to other sections of Minuartia, he hypothesized that its closest relatives were in M. sect. Spectabiles, likely in M. subsect. Biflorae. McNeill (1962) (Löve & Löve 1976), with L. biflora (L.) Á. Löve & D. Löve (≡ S. biflora) as type. Of these three names, Lidia is a nomenclatural synonym of Wierz bickia, as the two names have the same type. Cherleria has priority over Wierzbickia, although it has largely been overlooked because of the apparent dissimilarity of C. sedoides to the remaining members of Minuartia sect. Spectabiles. One member of Cherleria has recently received a new combination in the genus: C. laricifolia (L.) Iamonico.
For most of its history, when Cherleria was accepted, it was treated as a monotypic genus with only C. sedoides. However, various other species, now classified in several different genera, were also briefly considered to belong to Cherleria (Dillenberger & Kadereit 2014 and references therein).
Cherleria itself is divided into three major clades using molecular data (Table 1; Moore & Kadereit 2013), with one species, C. rupestris (Minuartia labillardierei Briq.; see Systematic treatment below) from Lebanon, having an uncertain position. Cherleria biflora and C. circassica are sister to the rest of the genus (Clade A). Although both are found in the Caucasus, C. biflora is also circumboreal, extending south into the Alps of Europe and the Sierra Nevada and Rocky Mountains of North America. Another clade (Clade B) contains three Arctic species (C. arctica, C. obtusiloba and C. yukonensis) that extend south into North America along the Rocky Mountains. These species form a polyploid complex (Löve & Löve 1976;Murray & Kelso 1997) and many questions remain in this clade, including how many times these plants colonized the C and S Rocky Mountains from the Arctic and N Rocky Mountains. This Arctic and North American clade is sister to a clade composed of European plants (Clade C) containing most of the species of Cherleria. Clade C is most diverse on the Balkan Peninsula (eight species) and in the Alps (four species).
Although these clades are generally geographically coherent, all three are quite morphologically heterogeneous. Therefore, we do not think they warrant taxonomic recognition at this time.

Material and methods
Species delimitations were guided in large part by our molecular work , where most species of Cherleria were clearly resolved as monophyletic. In particular, the molecular work guided us in the separation of C. biflora from C. obtusiloba in the United States and the S part of Canada, contrary to most current treatments (e.g. Rabeler & al. 2005;Hartman & Rabeler 2012). The morphology of the specimens we had sequenced, clear differences between the species in the few sets of specimens when both species were collected together, and Fernald's (1919) treatment allowed us to find morphological characters to separate them.
Neither molecular nor morphological data allowed us to draw strong boundaries between the species in Clade B (containing Cherleria arctica, C. obtusiloba and C. yukonensis), likely due in part to polyploidy. The relationships of the species in this clade are still in flux and merit further research.
Field work was performed in Europe (focusing on the Alps and Carpathians as well as Greece and Albania). The remaining species were examined from herbarium specimens, through herbarium visits and loans, with some additional types examined online. Herbarium abbreviations follow Index Herbariorum (Thiers 2016+) Mattfeld (1922) and McNeill (1962) and their placement in our phylogenetic trees based on DNA sequence data. All subsections and series are part of M. sect. Spectabiles unless noted otherwise.

Species
Mattfeld (  Cherleria arctica is present in the Asian and American Arctic. It has large white or pink petals and glandular, green or purple sepals with flattened (as opposed to hooded) tips. Its leaves have truncate (as opposed to pointed) tips, which are often purple. The leaves are generally glabrous, although a few individuals have glandular leaves, likely due to hybridization with C. obtusiloba or C. yukonensis. Cherleria baldaccii is a serpentine endemic restricted to Greece and Albania. It is distinctive in having larger flowers than the other Balkan species and short, creeping vegetative branches, instead of erect to ascending vegetative branches. Cherleria biflora occurs throughout the Eurasian and American Arctic, with additional populations in highalpine areas of the European Alps, the Asian Altai Mountains, the Caucasus, rarely in the mountains of E Canada, and the high mountains of W North America (being the only species of Cherleria in the Sierra Nevada of California and co-occurring with C. obtusiloba in the Cascades and Rocky Mountains). Throughout its range, C. biflora prefers mesic habitats, such as snowbanks and other areas where the soil remains moist throughout the short summer. Although it has been confused with C. obtusiloba in non-Arctic North America (e.g. Welsh 2003;Rabeler & al. 2005;Hartman & Rabeler 2012;Holmgren & Holmgren 2012), the two species are genetically distinct and unlikely to be able to interbreed (appearing in different major clades within Cherleria, Moore & Kadereit 2013) and often occur in different habitats (with C. obtusiloba generally occupying drier areas, where they co-occur). In addition, they can be distinguished morphologically as follows: sepals glabrescent at least at the tips and often recurved in fruit (C. biflora) versus glandular throughout and generally not recurved in fruit (C. obtusiloba); petals < 1.5 × sepals (C. biflora) versus > 2 × sepals (C. obtusiloba); leaves generally ± flat in cross-section and straight (C. biflora) versus clearly triangular in cross-section and generally at least somewhat curved (C. obtusiloba); old branches loosely covered with leaves from the previous year (C. biflora) versus densely covered with leaves (or their midribs) from previous years (C. obtusiloba); plants growing in small tufts or weak patches with small root systems (C. biflora) versus plants growing in dense patches with lower stems and roots clearly woody (C. obtusiloba). Cherleria capillacea (Fig. 1A) is widespread throughout the S Alps, Balkan Peninsula, SE France and Italy, always exclusively on calcareous substrates, generally on exposed limestone bedrock or scree. In addition to its habitat, C. capillacea can be distinguished by having leaves that are generally straight or slightly recurved (as opposed to twisted in various directions in C. garckeana, C. langii and C. laricifolia), always having glandular sepals (only glandular in C. garckeana and C. laricifolia subsp. diomedis), and with the lateral veins of the sepals ending c. ½ of the way to the tips (instead of c. ⅔ of the way to the tips in C. laricifolia and all the way to the tips in C. garckeana and C. langii). The plants on the Balkan Peninsula may be genetically distinct and merit recognition as a separate species, but more extensive study is needed. (10 -40 mm), triangular leaves that are evenly tapered from base to tip. The leaves are borne in rosettes, in which they are bent at the base so that they form an angle of 60° or more to the rosette axis (instead of borne in tufts, in which the leaves form angles of 30° or less to the rosette axis, which is the usual case in Cherleria, especially among species with leaves over 10 mm long). Cherleria dirphya is endemic to one small serpentine outcrop on the island of Evvia in Greece. It is endangered by goat grazing. It has straight, glaucous green leaves and petals that are narrower than the sepals, with flowers opening flat. (Hayek) A. J. Moore & Dillenb., comb. nov. ≡ Minuartia doerfleri Hayek in Oesterr. Bot. Z. 70: 12. 1921 ≡ Minuartia baldaccii subsp. doerfleri (Hayek) Hayek in Repert. Spec. Nov. Regni Veg. Beih. 1: 193. 1924 (Fig. 1F) is endemic to the Balkan Peninsula and adjacent Turkey and appears (according to herbarium records) to be a substrate generalist, growing on calcareous, siliceous and serpentine substrates, although most occurrences seem to be on serpentine-influenced substrates. It is morphologically quite similar to its relative C. laricifolia, but is always glandular pubescent in the inflorescence and has a nonoverlapping distribution.
Cherleria handelii is restricted to calcareous substrates on Cvrsnica Planina in Bosnia and Herzegovina. It is distinctive in being prostrate with the flowers borne on short stems < 1 cm long. Cherleria laricifolia is restricted to siliceous and occasionally serpentine substrates in the Alps (subsp. laricifolia), Apennines (subsp. ophiolitica), Pyrenees (subsp. diomedis) and SE France (subsp. diomedis and subsp. lari cifolia). Although it is not restricted to scree or bedrock as are C. capillacea and C. langii, it appears to be entirely absent from soils with influence of calcareous rocks.
Subsp. ophiolitica is restricted to serpentine soils of the N Apennines in Italy. It differs from the typical subspecies in having smaller flowers and more glaucous leaves, but is not completely distinct genetically and likely experienced significant gene flow during its divergence from subsp. laricifolia . ( Cherleria marcescens is endemic to serpentine substrates in Newfoundland, Labrador, Quebec, Canada, and one location in Vermont, U.S.A. Its leaves generally have the truncate tips typical of its relative C. arctica, but its flowers are much smaller and the plants are sprawling. The only species with which it slightly overlaps in distribution is C. biflora.  (Holmgren & Holmgren 2012); however, it does not correspond to Torrey's description, so the type material is either elsewhere or (more likely) has been lost, in which case a neotype must be designated.

Cherleria marcescens
Cherleria obtusiloba (Fig. 1D) is restricted to North America, ranging from the Arctic south along the Cas-cades and Rocky Mountains to New Mexico. Outside of the Arctic, it grows in alpine and subalpine habitats, often occupying rockier and drier sites than C. biflora. It appears to be entirely absent from California and the western two-thirds of Utah, but overlaps with C. biflora in the Cascades, Rocky Mountains and eastern mountain ranges of Utah. See the discussion of the differences between the two species under C. biflora.