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Dryad

Multilocus phylogeography, population genetics and niche evolution of Australian Brown and Black-tailed Treecreepers (Aves: Climacteris)

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Nov 20, 2022 version files 79.79 MB

Abstract

The Carpentarian barrier across northeastern Australia is a major biogeographic barrier and a generator of biodiversity within the Australian Monsoonal Tropics. Here we present a continent-wide analysis of mitochondrial (control region) and autosomal (14 anonymous loci) sequence and indel variation and niche modeling of Brown and Black-tailed Treecreepers (Climacteris picumnus and Cmelanurus), a clade with a classic distribution on either side of the Carpentarian barrier. mtDNA control region sequences exhibited reciprocal monophyly and strong differentiation (Fst = 0.91), and reveals a signature of a recent selective sweep in C. picumnus. No loci among 14 anonymous autosomal markers exhibited reciprocal monophyly between species, and a variety of tests support an isolation-with-migration model of divergence, albeit with low levels of gene flow across the Carpentarian barrier and a divergence time between species of ~1.7 – 2.8 MYA, depending on the model and assumptions about generation time. Paleo-ecological niche models show that both range size as measured by available habitat and estimated historical population sizes of both species declined in the last ~600 kyr and that the area of range overlap was never historically large, perhaps decreasing opportunities for extensive gene flow. The relatively long divergence time and low opportunity for gene flow may have facilitated speciation more so than in other co-distributed bird taxa across the Australian Monsoonal Tropics.