The Quaternary period was marked by significant climatic and sea-level fluctuations that had a strong impact on coastal ecosystems worldwide. Sea-level changes played a key role in the formation of restinga ecosystems along the Brazilian coast. These Quaternary sandy beach-dune deposits support unique ecosystems, characterized by their recent origin, constant environmental dynamics, and strong influence of saline, aeolian, and solar factors. The lizards Tropidurus hygomi, Glaucomastix abaetensis, and Glaucomastix itabaianensis are endemic and sympatric species found in restinga formations along the northern coast of Bahia and Sergipe. We used ddRADseq genomic data and ecological niche modeling to unravel the spatiotemporal diversification of these lizards across restinga areas. We found eight well-supported genetic population lineages in both lizard genera, revealing strong population structure. Spatial patterns of population clustering show a high degree of concordance across taxa. Gene flow among some lineages was associated with coastal plains, while barriers were linked to rivers, wetlands, and aeolian dune formations. We observed synchronous expansion of population lineages over the continental shelf during sea-level lowstands associated with glacial cycles, followed by synchronous population contraction during transgressive events in all population lineages. These patterns are associated with habitat availability and loss due to climatic changes and continental shelf exposure during the late Quaternary. Wetlands and river systems likely acted as barriers to gene flow, contributing to the observed population structure. We highlight the importance of genomic studies in other taxa to reveal the evolutionary and biogeographic processes linked to restinga ecosystems, and the urgent need for conservation efforts targeting these species and their habitats.
Fazolato et al. (Mon,) studied this question.