Data_Sheet_2_Convergent Morphological Evolution in Silene Sect. Italicae (Caryophyllaceae) in the Mediterranean Basin.csv

Recent divergence can obscure species boundaries among closely related taxa. Silene section Italicae (Caryophyllaceae) has been taxonomically controversial, with about 30 species described. We investigate species delimitation within this section using 500 specimens sequenced for one nuclear and two plastid markers. Despite the use of a small number of genes, the large number of sequenced samples allowed confident delimitation of 50% of the species. The delimitation of other species (e.g., Silene nemoralis, S. nodulosa and S. andryalifolia) was more challenging. We confirmed that seven of the ten chasmophyte species in the section are not related to each other but are, instead, genetically closer to geographically nearby species belonging to Italicae yet growing in open habitats. Adaptation to chasmophytic habitats therefore appears to have occurred independently, as a result of convergent evolution within the group. Species from the Western Mediterranean Basin showed more conflicting species boundaries than species from the Eastern Mediterranean Basin, where there are fewer but better-delimited species. Significant positive correlations were found between an estimation of the effective population size of the taxa and their extent of occurrence (EOO) or area of occupancy (AOO), and negative but non-significant correlations between the former and the posterior probability (PP) of the corresponding clades. These correlations might suggest a lower impact of incomplete lineage sorting in species with low effective population sizes and small distributional ranges compared with that in species inhabiting large areas. Finally, we confirmed that S. italica and S. nemoralis are distinct species, that S. nemoralis might furthermore include two different species and that S. velutina from Corsica and S. hicesiae from the Lipari Islands are sister species.

物种的近期分化常会模糊近缘类群间的物种界限。隶属于石竹科（Caryophyllaceae）的蝇子草属（Silene）意大利组（section Italicae）分类学争议较大，目前已描述的物种约有30个。本研究依托500份测序标本，针对1个核基因位点与2个质体基因位点，对该组开展物种界定研究。尽管仅使用了少量基因标记，但庞大的测序样本量使得我们能够可靠界定其中50%的物种。其余物种（如林地蝇子草Silene nemoralis、结节蝇子草S. nodulosa以及安德里亚蝇子草S. andryalifolia）的界定则更具挑战性。本研究证实，该组内10种岩隙植物（chasmophyte）中有7种之间并无近缘关系，反而与意大利组内地理分布邻近、生长于开阔生境的物种亲缘关系更近。由此可见，对岩隙生境的适应在该类群中独立起源，属于趋同演化的结果。西地中海盆地的类群相较于东地中海盆地的类群，其物种界限冲突更为显著；东地中海盆地的物种数量更少，但界定更为清晰。研究还发现，类群的有效种群大小（effective population size）估计值与其分布区范围（EOO，extent of occurrence）或占用面积（AOO，area of occupancy）呈显著正相关；而有效种群大小与对应分支的后验概率（PP，posterior probability）则呈负相关，但未达显著水平。这类相关性或表明，相较于分布区广阔的类群，有效种群规模较小、分布范围狭窄的类群受不完全谱系分选（incomplete lineage sorting）的影响程度更低。最后，本研究证实意大利蝇子草（S. italica）与林地蝇子草（S. nemoralis）为两个独立物种，林地蝇子草或可进一步划分为两个不同物种；同时来自科西嘉岛的绒叶蝇子草（S. velutina）与利帕里群岛的希塞蝇子草（S. hicesiae）为姊妹群。