The Quaternary evolutionary history of Bristol rock cress (Arabis scabra, Brassicaceae), a Mediterranean element with an outpost in the north-western Atlantic region

Kinetochore and ionomic adaptation to whole-genome duplication in Cochlearia shows evolutionary convergence in three autopolyploids

Whole-genome duplication (WGD) occurs in all kingdoms and impacts speciation, domestication, and cancer outcome. However, doubled DNA management can be challenging for nascent polyploids. The study of within-species polyploidy (autopolyploidy) permits focus on this DNA management aspect, decoupling it from the confounding effects of hybridization (in allopolyploid hybrids). How is autopolyploidy tolerated, and how do young polyploids stabilize? Here, we introduce a powerful model to address this: the genus Cochlearia, which has experienced many polyploidization events. We assess meiosis and other polyploid-relevant phenotypes, generate a chromosome-scale genome, and sequence 113 individuals from 33 ploidy-contrasting populations. We detect an obvious autopolyploidy-associated selection signal at kinetochore components and ion transporters. Modeling the selected alleles, we detail evidence of the kinetochore complex mediating adaptation to polyploidy. We compare candidates in independent autopolyploids across three genera separated by 40 million years, highlighting a common function at the process and gene levels, indicating evolutionary flexibility in response to polyploidy.

From Western Asia to the Mediterranean Basin: Diversification of the Widespread Euphorbia nicaeensis Alliance (Euphorbiaceae)

The Mediterranean Basin is an important biodiversity hotspot and one of the richest areas in the world in terms of plant diversity. Its flora parallels in several aspects that of the Eurasian steppes and the adjacent Irano-Turanian floristic region. The Euphorbia nicaeensis alliance spans this immense area from the western Mediterranean to Central Asia. Using an array of complementary methods, ranging from phylogenomic and phylogenetic data through relative genome size (RGS) estimation to morphometry, we explored relationships and biogeographic connections among taxa of this group. We identified the main evolutionary lineages, which mostly correspond to described taxa. However, despite the use of highly resolving Restriction Site Associated DNA (RAD) sequencing data, relationships among the main lineages remain ambiguous. This is likely due to hybridisation, lineage sorting triggered by rapid range expansion, and polyploidisation. The phylogenomic data identified cryptic diversity in the Mediterranean, which is also correlated with RGS and, partly, also, morphological divergence, rendering the description of a new species necessary. Biogeographic analyses suggest that Western Asia is the source area for the colonisation of the Mediterranean by this plant group and highlight the important contribution of the Irano-Turanian region to the high diversity in the Mediterranean Basin. The diversification of the E. nicaeensis alliance in the Mediterranean was triggered by vicariance in isolated Pleistocene refugia, morphological adaptation to divergent ecological conditions, and, to a lesser extent, by polyploidisation.