Abstract
BackgroundUnderstanding the relative influence of vicariance and dispersal in shaping Old World tropical biodiversity remains a challenge. We aimed to infer the roles of these alternative biogeographic processes using a species time-tree for the centipede genus Ethmostigmus from the Old World tropics. Additionally, we explored fine-scale biogeographic patterns for an endemic radiation of Ethmostigmus from the peninsular Indian Plate (PIP), an area with complex geological and climatic history.ResultsDivergence time estimates suggest that Ethmostigmus began diversifying in the Late Cretaceous, 99 (± 25) million years ago (Ma), its early biogeographic history shaped by vicariance. Members of Ethmostigmus in PIP form a monophyletic group that underwent endemic radiation in the Late Cretaceous, 72 (± 25) Ma. In contrast, a new species of Ethmostigmus from north-east India formed a clade with African/Australian species. Fine-scale biogeographic analyses in PIP predict that Indian Ethmostigmus had an ancestor in southern-central parts of the Western Ghats. This was followed by four independent dispersal events from the southern-central Western Ghats to the Eastern Ghats, and between different parts of the Western Ghats in the Cenozoic.ConclusionsOur results are consistent with Gondwanan break-up driving the early evolutionary history of the genus Ethmostigmus. Multiple dispersal events coinciding with geo-climatic events throughout the Cenozoic shaped diversification in PIP. Ethmostigmus species in PIP are restricted to wet forests and have retained that niche throughout their diversification.
Highlights
Understanding the relative influence of vicariance and dispersal in shaping Old World tropical biodiversity remains a challenge
We focused on the following questions: 1) When did Ethmostigmus start diversifying in peninsular Indian Plate (PIP)? Was the biogeographic history shaped by Gondwanan breakup or one/more long-distance dispersal events in PIP? 2) Given that Ethmostigmus species in PIP are largely restricted to the wet forests, were they influenced by Paleogene or Miocene or more recent Pleistocene climatic fluctuations and associated expansion and fragmentation of the forests?
The targeted group, Ethmostigmus, began its diversification in the Late Cretaceous, at 99 million years ago (Ma) (95% HPD range 150–54 Mya), when Australian species separated from other congeners
Summary
Understanding the relative influence of vicariance and dispersal in shaping Old World tropical biodiversity remains a challenge. The respective roles of biogeographic processes - vicariance and dispersal events - have repeatedly been debated, along with other ecological and evolutionary processes, to explain the origins and distribution of Old World tropical diversity [1, 2]. Many ancient lineages with Old World tropical distributions that could potentially be explained by Gondwanan vicariance remain to be explored using time-calibrated phylogenies with fossils in a quantitative biogeographic framework. Understanding the relative contribution of ancient vicariance and long-distance dispersal remains a challenge in accounting for the origins of Old World tropical diversity
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