Plant evolution in alkaline magnesium-rich soils: A phylogenetic study of the Mediterranean genus Hormathophylla (Cruciferae: Alysseae) based on nuclear and plastid sequences

Abstract

Habitats with alkaline edaphic substrates are often associated with plant speciation and diversification. The tribe Alysseae, in the family Brassicaceae, epitomizes this evolutionary trend. In this lineage, some genera, like Hormathophylla, can serve as a good case for testing the evolutionary framework. This genus is centered in the western Mediterranean. It grows on different substrates, but mostly on alkaline soils. It has been suggested that diversification in many lineages of the tribe Alysseae and in the genus Hormathophylla is linked to a tolerance for high levels of Mg+2 in xeric environments. In this study, we investigated the controversial phylogenetic placement of Hormathophylla in the tribe, the generic limits and the evolutionary relationships between the species using ribosomal and plastid DNA sequences. We also examined the putative association between the evolution of different ploidy levels, trichome morphology and the type of substrates. Our analyses demonstrated the monophyly of the genus Hormathophylla including all previously described species. Nuclear sequences revealed two lineages that differ in basic chromosome numbers (x = 7 and x = 8 or derived 11, 15) and in their trichome morphology. Contrasting results with plastid genes indicates more complex relationships between these two lineages involving recent hybridization processes. We also found an association between chloroplast haplotypes and substrate, especially in populations growing on dolomites. Finally, our dated phylogeny demonstrates that the origin of the genus took place in the mid-Miocene, during the establishment of temporal land bridges between the Tethys and Paratethys seas, with a later diversification during the upper Pliocene.

Multiple Drivers of High Species Diversity and Endemism Among Alyssum Annuals in the Mediterranean: The Evolutionary Significance of the Aegean Hotspot

“…Hook.f. Recent phylogenetic analyses, however, have revealed two major clades in Alyssum s.str., which do not agree with the traditional sectional classification ( Rešetnik et al, 2013 ; Li et al, 2015 ; Salmerón-Sánchez et al, 2018 ). One clade includes annual species of A. sect.…”

“…To estimate the divergence times of the studied species, we assembled an additional ITS alignment with a broader, tribe-wide taxonomic coverage. This alignment followed the dataset compiled by Salmerón-Sánchez et al (2018) , which comprised representatives of almost all genera of the tribe Alysseae ( Rešetnik et al, 2013 ; Španiel et al, 2015 ), complemented by the ITS sequences of annual Alyssum species generated in the present study and the ITS dataset of the perennial A. montanum–A. repens species complex (generated in Melichárková et al, 2019 ).…”

Odontarrhena stridii (Brassicaceae), a new Nickel-hyperaccumulating species from mainland Greece

“…This marker has been widely used in previous analyses of Alysseae and Alyssum s.l. for its useful phylogenetic signal (Warwick et al 2008;Cecchi et al 2010Cecchi et al , 2013Rešetnik et al 2013;Li et al 2015;Salmerón-Sánchez et al 2018;Melichárková et al 2019), while cpDNA sequences have usually only limited value for species delimitation and phylogenetic inference, as in the case of the related genus Alyssum (Zozomová-Lihová et al 2014;Španiel et al 2017). All sequences were retrieved from GenBank except for typical O. baldaccii from Crete, not previously investigated.…”

Data_Sheet_1.pdf

“…Hook.f. Recent phylogenetic analyses, however, have revealed two major clades in Alyssum s.str., which do not agree with the traditional sectional classification (Rešetnik et al, 2013;Li et al, 2015;Salmerón-Sánchez et al, 2018). One clade includes annual species of A. sect.…”