Evolution of Cardamine (Brassicaceae) perennials in Southwestern Asia and their phylogenetic relationships to related European polyploid species complexes.

Abstract

The area of Southwestern (SW) Asia, including the Caucasus and the Near East, comprises significant biodiversity hotspots and represents a cradle of lineage diversification for numerous plant groups. Yet, this region has been largely understudied from the biogeographic and phylogenetic perspectives.

In SW Asia, the genus Cardamine (Brassicaceae) is represented by several perennial endemics inhabiting wet habitats from lowlands up to the alpine belt, which are closely related to taxonomically complicated polyploid species complexes recognized in Europe, namely the C. amara group (represented here by C. lazica and C. wiedemanniana), C. pratensis and C. raphanifolia groups (in SW Asia represented by C. seidlitziana, C. tenera, and C. uliginosa). In contrast to numerous polyploids occurring in Europe, only the diploid level has been so far reported for these SW Asian representatives.

The SW Asian species have been considered to be distinguishable based on their distinct morphology and ecology. Previous molecular studies, however, did not allow to delimit them genetically, suggesting that either their evolution has been significantly and recurrently affected by interspecific gene flow, or that extensive ancestral polymorphisms are maintained.

In this study, we apply the combination of next-generation sequencing method involving target enrichment capturing >1000 nuclear genes with genome skimming (Hyb-Seq), and multivariate morphometrics, to 1) resolve whether the SW Asian taxa represent well-delimited biological entities as traditionally recognized; 2) address their evolutionary history and explain processes that have led to previously reported morphological and genetic discrepancies; 3) ascertain whether the Asian taxa represent a distinct evolutionary lineage that evolved independently from their European relatives, or whether their evolutionary histories have been largely shared and SW Asia served as an initial diversification center and a source of colonization of Europe. Acknowledgement: This study is supported by the Slovak Research and Development Agency APVV-17-0616 and Grant Agency of Czech republic GAČR 19-06632S.