Reassessing Colugo Phylogeny, Taxonomy, and Biogeography by Genome Wide Comparisons and DNA Capture Hybridization from Museum Specimens

Abstract

The ability to uncover the phylogenetic history of archived museum material with molecular techniques has rapidly improved due to the reduced cost and increased sequence capacity of next-generation sequencing technologies. However it remains difficult to isolate large, orthologous DNA regions across multiple divergent species. Here we describe the use of cross-species DNA capture hybridization techniques and next-generation sequencing to selectively isolate and sequence mitochondrial DNA genomes and nuclear DNA from the degraded DNA of museum specimens, using probes generated from the DNA of an extant species.

Colugos are among the most poorly understood of all living mammals despite their central role in our understanding of higher-level primate relationships. Two described species of these extreme gliders are the sole living members of a unique mammalian order, Dermoptera, distributed throughout Southeast Asia. We generated a draft genome sequence for a Sunda colugo and a reference alignment for the Philippine colugo, and used these to identify colugo-specific enrichment in sensory and musculoskeletal related genes that likely underlie their nocturnal and gliding adaptations. Phylogenomic analysis and catalogs of rare genomic changes overwhelmingly support the hypothesis that colugos are the sister group to primates (Primatomorpha), to the exclusion of treeshrews. We also captured ~140-kb of orthologous sequence data from colugo museum specimens sampled across their range, and identified deep genetic structure between many geographically isolated populations of the two named species, consistent with a remarkable increase in diversity. Our results identify conservation units to mitigate future losses of this enigmatic mammalian order.

Examining multiple distantly related mammals we identified a consistent pattern of early diversification between east and west Borneo including colugos, the lesser mouse deer, and pangolins. This strongly parallel biogeographic pattern is not common in mammals and we see no evidence for this pattern in the greater mouse deer. Colugos on West Borneo diverged from those in Indochina in the late Pliocene, however most other mammals across this same geographic region diverged from their common ancestor much more recently in the Pleistocene. Low genetic divergence between colugos on large landmasses and colugos on neighboring islands indicate that past forest distributions in the recent past were recently much larger than present refugial distributions.