Heterogeneous Signals of Selection in Antirrhinum

Identification of selection acting on individual genes can give important information about the selective pressures acting on the species. Selection is also a process of key importance in phylogenetics as it may obscure the inference of true species relationships. In the last decades several approaches have been developed to identify genes under selection, but until recently the analysis of multiple genes and the identification of multiple selection signals in the same group of species have not been possible with classic sequencing methods. Next-generation sequencing technology has increased the capacity to generate molecular data for phylogenetics, and has the potential to uncover multiple incongruent phylogenetic signals. Here we used hybrid-enrichment for capturing transcriptome (ESTs) genes in all Antirrhinum species, a model plant group for developmental and evolutionary research. We used tools from population genetics and phylogenetics to (i) identify regions of the ESTs that are more divergent than expected under a purely neutral model and (ii) identify alternative models of selection for each locus. The observed heterogenetity in the selection signal highlights the existence of complex multidirectional selection pressures acting on plant species.