Genealogical and niche modeling analyses reveal recent expansion and limited genetic divergence in the Formicivora serrana complex (Passeriformes: Thamnophilidae)

The principal aim of this study was to infer the phylogeographic pattern of the antwrens of the Formicivora serrana complex, an endemic faunal component of the semi-deciduous forests and restinga formations of the Atlantic Forest of southeast Brazil. We combined niche-based modeling and phylogeographic approaches in describing the genetic spatial structure of the taxon, inferring the phylogenetic hypothesis of lineage diversification, and providing estimates of population growth, timing of coalescence, and gene flow. We also modeled the species potential distribution to examine the putative consequences of the Last Glacial Maximum (LGM) (21,000 years ago) and Holocene climate variability. To perform this, we analyzed a dataset composed of two mitochondrial (cytochrome oxidase I and NADH dehydrogenase subunit 2) and four nuclear (anonymous loci) DNA regions from 35 specimens. Genealogical analyses were performed using phylogenetic maximum likelihood and coalescent Bayesian approaches; genetic diversity was assessed using analysis of molecular variance and network analysis; ages of coalescent events were estimated using a relaxed molecular clock model. Ecological niche modeling of current and LGM ranges were performed using six algorithms (Bioclim, general additive model, general linear model, Maxent, support vector machine and Random forest) based on 178 occurrence localities and 19 bioclimatic variables. Limited genetic divergence among recognized forms of the F. serrana complex was evidenced in the low mitochondrial nucleotide divergence among populations (Jukes–Cantor distance between subspecies varied from 0.17 to 0.21%), unresolved phylogenetic trees, star-shaped haplotype networks, and overall lack of population genetic structure. Fixation index analyses, however, suggested an incipient geographic structure. Ecological niche modeling suggested expansion of the distribution range since the LGM. Our results provide the first evidence that bird taxa of xerophytic and semi-deciduous habitats of the AF were also affected by Quaternary climatic fluctuations. The recovered genealogical pattern indicates that F. serrana should be regarded as a single evolutionary unit, corroborating current taxonomic hypotheses.