Diversification of Cerastium sylvaticum and C. subtriflorum on the margin of the south-eastern Alps

Abstract

The south-eastern Alps and the southerly adjacent areas are considered an important refugium for plant species during the Pleistocene glaciations; consequently, they harbour many endemic taxa. One of them is Cerastium subtriflorum, which in this area occurs sympatrically with morphologically similar, but more widespread C. sylvaticum. Here, we used amplified fragment length polymorphisms as well as ITS and plastid DNA sequences to explore phylogenetic relationships between the two species as well as their relationships to other Cerastium taxa previously deemed closely related. Our data show that both species are genetically well-differentiated sister taxa, but their relationship to other taxa remains unclear; both species rather form an independent evolutionary lineage within European Cerastium. Cerastium sylvaticum exhibits low genetic differentiation among populations in the investigated area, suggesting a single Pleistocene refugium in that part of Europe. The much more pronounced genetic differentiation within C. subtriflorum is likely a result of multiple Pleistocene refugia or more recent vicariance among the three disjunct partial distribution areas. Phylogenetic sequence data suggest hybridisation between the two taxa, resulting in a discordant phylogenetic position between ITS and plastid trees of one population of C. subtriflorum. Flow cytometric and multivariate morphometric analyses show that C. subtriflorum and C. sylvaticum differ in their genome size as well as in multiple morphological traits. We provide a taxonomic treatment for both species including an identification key and species descriptions.

Impact of Quaternary climatic oscillations on phylogeographic patterns of three habitat‐segregated Cerastium taxa endemic to the Dinaric Alps

“…sylvaticum and C . subtriflorum (Skubic et al, 2018) and is in line with observations that hybridisation within Cerastium is relatively common (Khalaf & Stace, 2000).…”

“…For instance, the haplotype in population 44 of C. grandiflorum was 17 mutational steps away from the haplotype found in the geographically closest studied population 42 (Figure 2g) but was close to the haplotypes of syntopic C. decalvans. A similar scenario was suggested in the case of co-occurring C. sylvaticum and C. subtriflorum (Skubic et al, 2018) and is in line with observations that hybridisation within Cerastium is relatively common (Khalaf & Stace, 2000).…”

Plant material selection, collection, preservation, and storage for nuclear DNA content estimation

“…These observations are not compatible with the high standards required for some applications, including the determination of absolute genome size [1, 15, 43]. Consequently, the majority of published studies have used preserved material solely to determine DNA ploidy levels, which can tolerate some relaxation of the quality criteria (e.g., [35,44–50]). In case a minor variation in DNA content is expected, it is advisable to calibrate the dried samples by a subset of samples analyzed from fresh tissues (e.g., [31]) to account for potential drop in the quality of analysis.…”

Phylogeny of Saxifraga section Saxifraga subsection Arachnoideae (Saxifragaceae) and the origin of low elevation shade‐dwelling species

“…They differ strongly in ecology. Whereas the calcifuge S. muscoides, not resolved as monophyletic in our phylogenetic tree, is a distinctly alpine species by occurring at elevations between 2250 and 4200 m (Kaplan, 1995;Webb & Gornall, 1989), S. tenella grows at between 700 and 2000 m on shady limestone rocks and screes, and S. presolanensis grows on north-facing and shady vertical or even overhanging limestone cliffs (Kaplan, 1995;Merxmüller & Wiedmann, 1957;Webb & Gornall, 1989) between 1800 and 2100 m. The range of S. tenella lies, as that of S. hohenwartii, in the 'southeasternmost calcareous Alps' refugium for calcicole taxa (Skubic et al, 2018;Tribsch & Schönswetter, 2003), and that of S. presolanensis, located on the very edge of the main range of S. muscoides, in the 'Alpi Bergamasche' refugium for calcicole taxa (Tribsch & Schönswetter, 2003). Although the range of S. tenella is elevations between 1730 and 3200 m (Kaplan, 1995) but mostly between 2100 and 2800 m (Webb & Gornall, 1989), S. arachnoidea grows between 600 and 1850 m in limestone dust under overhanging rocks (Pitschmann & Reisigl, 1959) sheltered from rain and sun (Webb & Gornall, 1989).…”