Genetic Diversification in a New Guinean Frog Genus ( Mantophryne , Microhylidae) was Driven by Ancient Tectonic Activity and Climate Reorganisation

ABSTRACT Western Melanesia sits at the junction of three major tectonic plates, characterised by dynamic plate interactions and geological diversity. Tectonic activity in this region has given rise to modern New Guinea, a relatively young island with extreme topographic heterogeneity and evolutionarily complex biota. New Guinea—particularly the East Papuan Composite Terrane (EPCT)—supports exceptional frog diversity; however, evolutionary histories of many frogs of the EPCT are poorly understood. The microhylid frog genus Mantophryne currently includes five described species ( M. axanthogaster , M. insignis , M. louisiadensis , M. menziesi and M. lateralis ), with the first four confined to small portions of the EPCT and the last distributed across the eastern half of New Guinea. The biogeographic history of these frogs remained incompletely resolved at the time of our study. We estimate that Mantophryne diverged from other microhylid genera approximately 14.4 million years ago (MYA) and began to speciate ca. 8.5 MYA. We recover eight distinct lineages within frogs assigned to M. lateralis , which started to diverge ca. 5.5 MYA. Dispersal of Mantophryne out of the EPCT occurred in the late Pliocene, around the time the Central Highlands expanded eastward to connect with the EPCT. Six pairs of sister lineages arose during a time of significant climate reorganisation in the Late Pliocene—Early Pleistocene when it is possible that areas to the north of the Central Highlands experienced increased precipitation, while areas south of the Central Highlands experienced lower rainfall, resulting in contraction of rainforests and expansion of savannahs. We did not identify any significant differences in habitus between lineages, other than M. louisiadensis which is much larger than all other Mantophryne, and has exceptionally high sexual‐size dimorphism. While an interrogation of the putative cryptic species complex within the M. lateralis clade is beyond the scope of our study, we find that a combination of tectonic rearrangement and climatic history are likely responsible for most of the diversity within the genus that we see today.