Multilocus analysis of intraspecific differentiation in three endemic bird species from the northern Neotropical dry forest.

Among-species phylogeographic concordance provides insight into the common processes driving lineage divergence in a particular region. However, identifying the processes that caused phylogeographic breaks is not always straight forward, and inferring past environmental conditions in combination with documented geologic events is sometimes necessary to explain current patterns. We searched for concordant phylogeographic patterns and investigated their causes in three bird species (Momotus mexicanus, Melanerpes chrysogenys, and Passerina leclancherii) that belong to three different avian orders and are endemic to the northernmost range of the Neotropical dry forest. We obtained mitochondrial DNA (ND2 and COI or cyt b) and nuclear DNA (20454, GAPDH, MUSK, and TGFB) sequences for at least one locus from 162 individuals across all species and defined climatically stable areas using environmental niche model projections for the last 130,000 years to have a paleoenvironmental framework for the phylogeographic results. All three species showed marked phylogeographic structure, with breaks found in roughly similar areas, such as the border between the Mexican states of Guerrero and Oaxaca, and between southern Jalisco and Michoacán. Both of these regions are known biogeographic breaks among other taxa. Patterns of genetic diversity and differentiation were partially compatible with climatically stable areas. Coalescent analyses revealed recent population growth and estimated the deeper haplogroup divergence of all three taxa to have occurred within the last 600,000 years. The phylogeographic patterns found are noteworthy because they are maintained in a relatively small area for bird species with continuous ranges, and highlight a unique situation when compared to phylogeographic patterns found in other studies of Neotropical birds that have stressed the role of geographic barriers to explain intraspecific differentiation. Our results point to a scenario of population isolation resulting in the present phylogeographic structure, likely a result of historical climate fluctuations that have fragmented and reconnected the Neotropical dry forest. This study contributes to a growing body of evidence indicating active diversification of endemic lineages in the northern Neotropical dry forest region.