Population structure of endemic Atlantic Forest spiny rats Trinomys dimidiatus and Trinomys iheringi (Echimyidae)

The Atlantic Forest has experienced a significant loss of its original vegetation, with more than 80% of the biome now comprising small and isolated fragments. To understand species distribution, it is crucial to comprehend the impact of fragmentation on species persistence within this biome. Previous phylogeographic inferences have indicated that Trinomys iheringi and T. dimidiatus are structured into two populations each. In this study, we employed a more comprehensive database to re-examine the phylogeography and conduct a detailed analysis of the demographic history and population structure of two Trinomys species. The results indicate that T. dimidiatus is structured into at least three populations clusters: Serra dos Órgãos, South Center of Serra do Mar, and North of Serra do Mar. T. iheringi is highly structured into two populations: São Paulo and Ilha Grande. The demographic analysis indicated that T. dimidiatus from Serra do Mar exhibited an expansionist trend previously the Last Glacial Maximum (LGM). In contrast, T. iheringi experienced an expansion of suitable areas onto the emergent continental shelf during the LGM. Additionally, T. iheringi includes an entirely isolated island population exhibiting no gene flow, and analysis suggests the presence of a new microendemic species. The results presented here indicate that Trinomys species have complex genetic structure patterns that show the importance of Atlantic Forest ecosystem conservation.