Comparative Phylogeography of the Northern Australian Monsoon Tropics by Whole Genome Resequencing of two Species of the Avian Genus Climacteris

Abstract

Abstract Phylogeography combines geographic information with phylogenetic analysis to gain insight into the origin, dispersal, and speciation dynamics of populations. Advances in the utility of Next Generation Sequencing technology has led to a shift toward whole genome sequencing for analyzing contemporary geographic patterns and how they have arisen. A geographic area and its history can help to tell a story of how organisms change genetically over time. This idea is illustrated by one area of geography that was affected by climatic conditions during the Pleistocene epoch. During the Pleistocene, the monsoon tropics of Northern Australia were affected by climatic and sea level fluctuations due to global cycles of glaciation and glacial receding in other areas of earth that altered sea levels intermittently across the region. This caused formation and deformation of a land bridge comprising a 150km area separating the Top End of Australia from the Cape York Peninsula This is the so- called Carpentarian Barrier (CB) and numerous studies investigating many clades have shown replicated vicariance around this barrier due to intermittent genetic exchange. Two sister species from the genus Climacteris have ranges that the CB splits with negligible overlap. Climacteris melanura and Climacteris picumnus range to the west and to the east of the barrier, respectively. Therefore, we hypothesize that these species have formed by intermittent gene exchange caused by the opening and the closing of the land bridges over time. There should be evidence of introgression and reticulate evolution when comparing populations to the east of the CB and to the west of the CB. This study looks for this evidence by performing whole genome resequencing of populations on both sides of the barrier and mapping these sequences to a de novo Reference of a C. picumnus individual. We find that there is evidence of introgression between C. melanura to the west of the CB and C. picumnus to the east of the CB by performing ABBA-BABA analysis on individuals around the barrier. We support this finding with additional investigation into statistical measures that infer genetic diversity and variability (π, polymorphic sites and Principal Component Analysis). This study will add to other similar investigations on this area and may add to the growing breadth of insight that could lead to signals of gene tree heterogeneity across Northern Australia.