Phylogeography of the Caesalpinia hintonii complex (Leguminosae: Caesalpinioideae: Poincianella)

Abstract

Although many phylogeographic studies have been conducted to analyze the genetic and phylogeographic structure of Mexican species, such studies are nearly absent for plants of dry seasonal forest, precincts with high level of endemism. To better understand this areas, we undertook a phylogeographic study and dating were carried out on the Caesalpinia hintonii complex distributed in the Río Balsas Depression and Tehuacán-Cuicatlán Valley. The phylogeographic structure was determined analyzing sequences from 4 plastid regions (trnL, trnL-F, psbA-trnH and accDpsaI) in all populations. A nonparametric rate smoothing (NPRS) method was employed to estimate the time of origin of the species complex. Haplotypic (0.64-1) and the nucleotide differences (3.8-11.52) were high in all species. The morphologically indistinct C. oyamae populations are genetically structured and showed 3 haplogroups where gene flow is low; considered them here as cryptic entities. The C. hintonii populations are genetically close-knit, even though they are morphologically distinct. The populations of C. macvaughii exhibit 2 divergent lineages with gene flow (Nm=1.41). Divergence events in 2 lineages between east and west from Rio Balsas Depression can be explained by geologic events. Our results showed that the C. hintonii complex is under diversification and in some cases morphostatic radiation.