Isolation by marine barriers and climate explain areas of endemism in an island rodent

Abstract

AbstractAimThe Indonesian island of Sulawesi is home to thousands of endemic terrestrial animal species. Phylogeographical studies of some of these taxa revealed concordant distribution patterns (areas of endemism; AoEs), suggestive of a shared evolutionary or ecological mechanism driving divergence among various terrestrial taxa. Generally, AoEs have been attributed to Pleistocene marine incursions, geological fault zones and Sulawesi's history as an archipelago. We test, for the first time, the hypothesis that population divergences are associated with unsuitable climate spaces at the boundaries between these areas.LocationSulawesi, Indonesia.TaxonMaxomys musschenbroekii, a common murid rodent endemic to Sulawesi.MethodsWe sequenced a mitochondrial gene, four nuclear protein‐coding genes and hundreds of ultraconserved elements from individuals sampled across the island, which we used to build intraspecific phylogenies and identify population structure. To test climate‐related hypotheses, we used multiple regression to assess the extent to which genetic distances, over‐land geographical distances, environmental distances (derived from ecological niche model resistance surfaces) and areas of endemism are correlated.ResultsIn all three genetic datasets, we inferred phylogeographical structure that is geographically concordant with previously defined AoEs. Ecological niche models showed a similar geography of suitability across the island since the Last Glacial Maximum, with varying levels of unsuitable climate space between AoEs. Genetic distances were more strongly correlated with environmental distances than geographical distances and interspecific divergences arose just in the past 1.5 Myr.Main ConclusionsPopulation divergences within M. musschenbroekii are consistent with AoE definitions from other taxa. Stable areas of unsuitable habitat near AoE boundaries probably supplemented marine incursions in generating population structure within M. musschenbroekii and other co‐distributed species.