Contemporary genetic structure of Xantus's Hummingbird (Basilinna xantusii) in the Baja California peninsula

Abstract

Genetic structure and phylogeographic patterns of natural populations are of great importance in assessing the conservation status of species. These population properties can be estimated using molecular markers of either mitochondrial DNA (mtDNA) or nuclear DNA (nDNA) to understand the historical, ecological and dispersal patterns that influence genetic exchange within and between populations. Basilinna xantusii is a sexually dimorphic hummingbird endemic to the Baja California Peninsula (BCP). It comprises three ancestral mitochondrial lineages linked to vicariant events, late Pleistocene climate changes and the geographical distribution of oases. This study aimed to determine and understand the current population genetic structure of this hummingbird. The genotypes of 16 microsatellite loci from 100 individuals collected across the geographical range of this species were compared with mtDNA sequences previously published. Cluster analyses identified five populations, two with almost no genetic admixture in the northern part of the BCP and three others with varying levels of admixed ancestry across the BCP. In San José de Magdalena, at the northernmost end of the range of Xantus's Hummingbird, 40% of individuals collected belong to one genetic cluster and the remaining 60% to another, both genetic clusters showing very little admixed ancestry. We hypothesize that, despite being in sympatry, these individuals do not interbreed, unlike the other populations where individuals showed ancestry coefficients of the other genetic groups. The philopatric behaviour of males and the long‐range dispersal capacity of females probably determine the observed genetic differentiation pattern. The mito‐nuclear discordance detected could be due to the molecular markers used and to female‐biased dispersal. Gene flow is asymmetric in this species, being greater from north to south than vice versa, which is probably related to differences in the seasonality of precipitation across the BCP and to urbanization of the oases.