Comparative phylogeographic and demographic analyses reveal a congruent pattern of sister relationships between bird populations of the northern and south-central Atlantic Forest

The Pernambuco Center of Endemism (PCE) is the northernmost strip of the Atlantic Forest (AF). Biogeographic affinities among avifaunas in the PCE, the southern-central Atlantic Forest (SCAF), and Amazonia (AM) have not been studied comprehensively, and current patterns of genetic diversity in the PCE remain unclear. The interplay between species' ecological attributes and historical processes, such as Pleistocene climate fluctuations or the appearance of rivers, may have affected population genetic structures in the PCE. Moreover, the role of past connections between the PCE and AM and the elevational distribution of species in assembling the PCE avifauna remain untested. Here, we investigated the biogeographic history of seven taxa endemic to the PCE within a comparative phylogeographic framework based on a mean of 3,618 independent single nucleotide polymorphisms (SNPs) extracted from flanking regions of ultraconserved elements (UCEs) and one mitochondrial gene. We found that PCE populations were more closely related to SCAF populations than they were to those in AM, regardless of their elevational range, with divergence times placed during the Mid-Pleistocene. These splits were consistent with a pattern of allopatric divergence with gene flow until the upper Pleistocene and no signal of rapid changes in population sizes. Our results support the existence of a Pleistocene refugium driving current genetic diversity in the PCE, thereby rejecting the role of the Sao Francisco River as a primary barrier for population divergence. Additionally, we found that connections with Amazonia also played a significant role in assembling the PCE avifauna through subsequent migration events.

Automated summary

The Pernambuco Center of Endemism (PCE) is a northern strip of the Atlantic Forest, where genetic diversity is influenced by ecological factors and historical processes. Population splits within the PCE occurred during the Mid-Pleistocene, with closer relations to southern-central Atlantic Forest populations than those in Amazonia. The study supports the role of Pleistocene refugium in shaping current genetic diversity in the PCE, while also highlighting connections with Amazonia in assembling the PCE avifauna through migration events.