Species delimitation within Silene aegyptiaca populations from Southeastern Anatolia

In systematic studies, species are regarded as the fundamental units of biological classification, and accurate species delimitation is essential for the proper assessment of biodiversity. Silene aegyptiaca is an annual plant widely distributed throughout the eastern Mediterranean region. Recent molecular studies have revealed that S. aegyptiaca represents a species complex exhibiting considerable genetic diversity. However, these studies included only a limited number of samples from Turkey's Southeastern Anatolia Region and therefore did not fully capture the extent of genetic variation present in this area. The present study aims to identify the potentially divergent lineages of S. aegyptiaca occurring In Southeastern Anatolia within a multispecies coalescent (MSC) framework. To this end, DNA sequences were obtained from six unlinked loci commonly employed in previous phylogenetic analyses of the genus Silene, and the resulting dataset was analyzed using the STACEY method. The results are consistent with previous studies, indicating the presence of two to four distinct genetic lineages within the Southeastern Anatolian populations of S. aegyptiaca. The observed genetic diversity appears to be incongruent with the species' currently accepted taxonomic boundaries. STACEY analyses revealed that the examined populations represent discrete and independent evolutionary lineages, with these divergences being strongly supported by high posterior probability (PP) values. The inferred species tree showed that populations are clustered into five major groups, largely independent of their geographic distribution. Furthermore, species delimitation analyses identified at least four genetically differentiated lineages. In conclusion, although S. aegyptiaca appears morphologically homogeneous, it possesses a complex genetic structure comprising multiple evolutionary lineages. These findings underscore the importance of elucidating the underlying causes of the observed genetic diversity and suggest that the current taxonomic status of the species should be re-evaluated in light of these results.