Evolutionary networks from RADseq loci point to hybrid origins of Medicago carstiensis and Medicago cretacea

• Premise Although hybridization has played an important role in the evolution of many plant species, phylogenetic reconstructions that include hybridizing lineages have been historically constrained by the available models and data. Restriction-site-associated DNA sequencing (RADseq) has been a popular sequencing technique for the reconstruction of hybridization in the next-generation sequencing era. However, the utility of RADseq for the reconstruction of complex evolutionary networks has not been thoroughly investigated. Conflicting phylogenetic relationships in the genus Medicago have been mainly attributed to hybridization, but the specific hybrid origins of taxa have not been yet clarified. Methods We obtained new molecular data from diploid species of Medicago section Medicago using single-digest RADseq to reconstruct evolutionary networks from gene trees, an approach that is computationally tractable with data sets that include several species and complex hybridization patterns. Results Our analyses revealed that assembly filters to exclusively select a small set of loci with high phylogenetic information led to the most-divergent network topologies. Conversely, alternative clustering thresholds or filters on the number of samples per locus had a lower impact on networks. A strong hybridization signal was detected for M. carstiensis and M. cretacea, while signals were less clear for M. rugosa, M. rhodopea, M. suffruticosa, M. marina, M. scutellata, and M. sativa. Conclusions Complex network reconstructions from RADseq gene trees were not robust under variations of the assembly parameters and filters. But when the most-divergent networks were discarded, all remaining analyses consistently supported a hybrid origin for M. carstiensis and M. cretacea.

Subject headings

NATURVETENSKAP  -- Biologi -- Botanik (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Botany (hsv//eng)

Keyword

alfalfa

assembly

Fabaceae

GBS

gene trees

hybridization

Medicago

multidimensional scaling

bayesian-inference

sequence capture

hybridization

introgression

phylogeny

model

demography

thousands

history

taxa

Plant Sciences

Publication and Content Type

ref (subject category)

art (subject category)