Persistence in peripheral refugia promotes phenotypic divergence and speciation in a rainforest frog

Area of Science:

• Evolutionary Biology
• Phylogeography
• Speciation Research

Background:

• Late Quaternary climate fluctuations demonstrably altered species distributions.
• The mechanisms by which climate change drives phenotypic divergence and speciation remain less understood.
• Intraspecific lineage analysis within refugia offers a pathway to investigate climate-driven speciation.

Purpose of the Study:

• To investigate if climate-mediated distribution shifts promoted genetic and phenotypic divergence in the Australian rainforest frog Cophixalus ornatus.
• To assess the role of refugial isolation in the Australian Wet Tropics (AWT) during Pleistocene glacial periods.
• To determine if distinct lineages within Cophixalus ornatus represent nascent or established species.

Main Methods:

• Paleomodeling to reconstruct past climate and distributions.
• Multilocus genetic analyses to assess lineage divergence and gene flow.
• Comparative analysis of ecologically relevant morphology and mating calls.
• Contact zone analyses to infer species boundaries.

Main Results:

• Paleomodeling and genetic data confirmed long-term persistence and isolation of Cophixalus ornatus lineages within three AWT refugia.
• Three major lineages exhibited divergence in morphology and mating calls, unlike other AWT vertebrates.
• Divergence in mating calls and contact zone patterns suggest these lineages may represent distinct species.

Conclusions:

• Climate shifts during the late Quaternary can drive significant genetic and phenotypic divergence.
• Refugial isolation coupled with divergent selection or genetic drift can lead to speciation.
• Incorporating adaptive traits into phylogeographic studies is crucial for understanding speciation mechanisms.