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Abstract The Carpentarian barrier across north-eastern 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 modelling of brown and black-tailed treecreepers (Climacteris picumnus and Climacteris melanurus), 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 revealed a signature of a recent selective sweep in C. picumnus. 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. Palaeoecological niche models show that both range size as measured by available habitat and estimated historical population sizes of both species declined in the past ~600 kyr and that the area of interspecific 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. 

The Neotropical microhylid genus Synapturanus was represented by only three species for almost five decades and remains poorly known. Recently two new species were described from the Eastern Guyana Shield, one from Peru, and one from Brazil. We describe three new species related to the S. rabus species complex with known distribution only in western Amazonia, Colombia. The S. rabus complex consists of the smallest species in the genus; one of the new species is slightly larger than S. rabus and we describe its full osteology; the other two new species are smaller than S. rabus. Wealso described the call and larvae of one of the new species. We provide an updated diagnosis and review the available molecular and phenotypic data for the genus.