Phylogeny of the Pilosocereus genus (Cactaceae) and coalescent-based species delimitation in the Pilosocereus aurisetus group using multilocus data

Abstract

The recent development of new probabilistic methods based on the multispecies coalescent model has enabled the hypothesis testing of species delimitation even in groups that originated recently, with tiny morphological distinction among lineages and complex geographic variation among populations. Among the most diverse genera of Cactaceae in Brazil, Pilosocereus comprises 41 recognized species and is subdivided into five informal taxonomic groups based on morphological and geographical groupings. Among these groups, P. aurisetus comprises eight species restricted to enclaves of rocky savannas in the center and eastern Brazil. These species show an intricate phylogeographical history with recent diversification, presence of cryptic lineages and a taxonomy of difficult formal treatment. From a database obtained by a massive sequencing of fragments associated to restriction sites (Rad-Seq) in an inter and intraspecific sample of P. aurisetus group, we developed and validated in silico and in vitro a suite of anonymous nuclear loci and microsatellites useful for phylogenetic and phylogeographic studies in the Pilosocereus genus. Here, we will use these markers to 1) investigate the phylogenetic relationships and the species composition in the informal taxonomic groups of the Pilosocereus genus; 2) use a coalescent approach of species delimitation to investigate the taxonomic diversity into the phylogenetic lineage related to the P. aurisetus group. The results of this study will be used to make explicit recommendations on the formal taxonomic treatments of the genus that will certainly be necessary to achieve a taxonomic arrangement that accurately reflects the diversity in the group of species studied. (AU)