A project undertaken at the Department of Zoology, University of Melbourne, and supervised by Paul Oliver
New Guinea is the fourth largest island on earth, and is a world hotspot of biological diversity and endemism. However it also remains one of the most poorly explored areas on earth. Few comprehensive molecular and morphological assessments of diversity have yet been undertaken within any diverse lineage from New Guinea. We also have little understanding of the historical processes that have generated New Guinea’s wealth of biological diversity. These gaps in understanding have major consequences for understanding the distribution and evolution of a diverse tropical island biota increasingly threatened by habitat loss and climate change.
Figure 5. Cyrtodactylus medioclivus:a newly described species of gecko endemic lower montane forest on the central cordillera. This species is most closely related to another lower montane endemic species currently known only from geographically distant north coast ranges of New Guinea. Photograph. S. Richards.
This project aimed to address these issues by completing and comparing molecular and morphological assessments of species diversity, phylogenetic relationships and biogeographic history within two lineages of frogs and one lineage of lizards.
Tiny frogs: Albericus/Choerophyrne
Our honours student working on this project has compiled a near complete phylogeny for Choerophyrne, and a comprehensive phylogeny for Albericus. Analysis of evolutionary patterns in the former suggest that multiple lineages have independently colonised montane regions, that montane diversity in the north coast ranges is especially young and derived, and that body size and ecology (terrestrial vs arboreal) are all highly plastic and show some evidence of correlation (terrestrial montane species seem to be consistently amongst the the smallest). We also now have CT scans for over 20 species in this group, these have revealed unique anatomical structures and synapomorphies that we are in the process of properly characterising. At least five new species have also been discovered.
Big green gliding frogs: Litoria graminea group
This spectacular group of large green frogs clearly consists of a radiation of outwardly similar lowland lineages that have mostly been lumped within a single species. However because of patchy sampling we need additional phylogenetic data to confirm the evolutionary distinctiveness of some of the divergent lineages we have identified. Morphological analyses have also revealed that one lineage within this radiation is characterised by increasing webbing on the hands – outwardly this seemed unusual for these highly arboreal frogs, however it appears to be an instance of convergent evolution. Field observations indicate that this webbing is an adaptation for parachuting, similar to behaviours recorded in frogs from Asia and America
Giant Geckos: Cyrtodactylus
Despite being a predominately a lowland group, we have confirmed that at least one lineage (consisting entirely of new species recognised in the last five years) has adapted to montane habitats. The wide and disjunct distribution and low genetic diversity of species in this lineage also suggest that (contra the pattern in Choerophyrne) there has been significant recent geneflow between montane isolates. Analysis of body size evolution in these geckos has also revealed a fundamental shift in evolutionary trajectory as this widespread radiation crossed Wallace’s Line; Melanesian species are far larger than their Asian relatives. This shift in evolutionary trajectory appears to be correlated with evolutionary release after crossing through this famous biogeographic zone. Finally, we have also discovered at least eight previously unrecognized species.
The datasets we have gathered have greatly improved the resolution of species identifications in field surveys undertaken for both consultancies and Non-government organisations. Providing data to improve species identifications in the field was one of our key initial aims, and this result is particularly pleasing.
Oliver and Richards are both also involved on ongoing IUCN assessments of the conservation status and distribution of the New Guinea Herpetofauna. New systematic data from this project is feeding into these assessments and greatly improving our understanding of the distribution and conservation status of biodiversity in New Guinea.
Finally this project has provided support for an enthusiastic early career researcher (Amy Iannella) at the University of Adelaide and South Australian Museum, who is now enrolled in PhD program in the sciences.
Related publications accepted or in press:
Oliver, P.M., Skipwith, P., Lee, M.S.Y. (Accepted) Crossing the line: shifting body size optima in a trans-Wallacean lizard radiation. Biology Letters.
Richards, S.J., Oliver, P.M., Brown, R.M. (2014) A new scansorial species of Platymantis (Anura: Ceratobatrachidae) from Manus Island, Admiralty Archipelago, Papua New Guinea. Biodiversity, biogeography and nature conservation in Wallacea and New Guinea. 2, 123–133.
Skipwith, P., Oliver, P.M. (2014). A new Gehyra (Gekkonidae: Reptilia) from New Guinea with unique caudal scalation. Zootaxa. 3827, 057–066.
Günther, R., Richards, S.J. and Dahl, C. (2014) Nine new species of microhylid frogs from the Muller Range in western Papua New Guinea (Anura, Microhylidae). Vertebrate Zoology. 64, 59-94.
Iannella, A. Oliver, P.M., Richards, S.J. (2014) A new species of Choerophryne (Anura, Microhylidae) from the Central Cordillera of Papua New Guinea. Zootaxa 3753, 483–493
Oliver, P.M. and Richards, S. (2012) A new species of small bent-toed gecko (Cyrtodactylus, Gekkonidae) from the Huon Peninsula, Papua New Guinea. Journal of Herpetology. 46,488–493.
Oliver, P.M., Sistrom, M. and Richards, S. (2012) The Cyrtodactylus of Melanesia, preliminary phylogeny and description of two new species. Zoologica Scripta. 41, 437–454.
Oliver, P.M. and Richards, S. (2012). Two new species of Callulops (Anura: Microhylidae) from montane New Guinea. Zootaxa. 3178, 33–44.