Herpetology

Biodiversity of frogs in Southeast Asia

 
As part of an international collaboration we study diversity, evolution and phylogenetic relationships of the frogs of Borneo, one of the most famous biodiversity hotspots on earth. The basic idea of our project is to build an inventory of the amphibian species richness including their larval stages. 
 
Field work
During our field work we collect frogs, tadpoles and tissue samples to increase our reference collections and to collect the material for subsequent studies of morphology and phylogeny. Moreover, we document habitats, geographic locality data and species composition of the amphibian communities.
 
Identification of tadpoles
In the biphasic life cycle of anurans the larvae (tadpoles) play a crucial role for the understanding of ecology, evolution and diversity of frog communities in the different types of tropical habitats. Tadpoles of numerous species are still unknown or misidentified in literature, new species of frogs continue to be discovered. We use fast evolving genetic markers for the unequivocal matching of tadpoles and frogs (genetic barcoding, 16S and 12S mt rDNA). Laboratory work is conducted in the gene lab at the Natural History Museum Bern.
 
Description of tadpoles
After the reliable identification we want to provide detailed and standardised descriptions of tadpoles of all Bornean frog species. The formal desciptions are published including color pictures, ink or vector drawings and REM images. More information and an impression of the diversity of Bornean frogs and their often bizarre larvae you can find on our homepage: www.frogsofborneo.org.
 
3d reconstructions
Morphological descriptions and comparisons based on modern techniques like computer-aided 3d reconstructions provide the basis for the understanding of evolutionary adaptations of tadpoles. Exemples for highly specialised anuran larvae are the fossorial tadpoles of Leptobrachella, the macro-carnivorous tadpoles of Occidozyga, and the the convergently evolved stream dwelling, rheophilic tadpoles of different genera (Ansonia, Rhacophorus, Meristogenys).
 
Phylogeny reconstructions
The phylogeny of several groups of frogs of Borneo remains to be reconstructed and, therefore, the taxonomy is often in a doubtful state. Phylogenetic analyses using morphological and molecular data (sequences of mitochondrial and nuclear genes) as well as resulting taxonomic revisions are further projects.
 
Phylogeography and taxonomy
Furthermore we are interested in the reconstruction of the histrical processes that lead to the current distribution of frogs on Sundaland. We study therefore the of biogeography of the populations of different species of frogs on Borneo and the other islands of Sundaland using morphology of adults and larvae, molecular genetics and bioacustics. These integrative analyses result in improvments in understanding the diversity of amphibians. Finally, the combined usage of different sources of information in particular mitochondrial and nuclear markers allows the delimitation of species and the recognition of cryptic species.
 
Selected publications:
 
Oberhummer, E., Barten, C., Schweizer, M., Das, I., Haas, A., Hertwig, S.T., accepted. Description of the tadpoles of three rare species of megophryid frogs (Amphibia: Anura: Megophryidae) from Gunung Mulu, Sarawak, Malaysia. Zootaxa.
 
Hertwig, S.T., Pui, Y.M., Haas, A., Das, I., 2014. Dressed in Black. A New Ansonia Stoliczka, 1870 (Lissamphibia: Anura: Bufonidae) from Gunung Murud, Sarawak, East Malaysia (Borneo). Zootaxa, 3814 (3): 419–431.
 
Das, I., Pui, Y.M., Hsu, W.W., Hertwig, S.T., Haas, A., 2014. Red Hot Chili Pepper. A New Calluella Stoliczka, 1872 (Lissamphibia: Anura: Microhylidae) from Sarawak, East Malaysia (Borneo). Zootaxa, 3785 (4): 550–560.
 
Haas, A., Pohlmeyer, J., McLeod, D., Kleinteich, T., Hertwig, S.T., Das, I., Buchholz, D.R., 2014. Extreme tadpoles II: the highly derived larval anatomy of Occidozyga baluensis (Boulenger, 1896), an obligate carnivorous tadpole. Zoomorphology, DOI 10.1007/s00435-014-0226-7.
 
Hertwig, S.T., Schweizer M., Das, I., Haas, A., 2013: Diversification in a biodiversity hotspot – the evolution of Southeast Asian rhacophorid tree frogs on Borneo (Amphibia: Anura: Rhacophoridae). Molecular Phylogenetics and Evolution 68, 567-581.
 
Haas, A., Hertwig, S.T., Krings, W., Braskamp E., Dehling J.M., Pui, Y.M., Jankowski, A., Schweizer, M., Das, I. (2012): Description of three Rhacophorus tadpoles (Lissamphibia: Anura: Rhacophoridae) from Sarawak, Malaysia (Borneo). Zootaxa, 3328: 1-9.
 
Hertwig, S.T., Lilje, K.E., Pui, Y.M., Haas, A., Das, I. (2012): Evidence of direct development in the rhacophorid frog Philautus acutus (Rhacophoridae, Anura) from Borneo. Raffles Builletin of Zoology, 60, 559 -568.
 
Wildenhues, M., Rauhaus, A., Bach, R., Karbe, D., van der Straeten, K., Hertwig, S.T., Ziegler, T. (2012): Husbandry, captive breeding, larval development and stages of the Malayan horned frog Megophrys nasuta (Schlegel, 1858) (Amphibia: Anura: Megophryidae). Amphibian and Reptile Conservation 5(3):15-28.
 
Hertwig, S.T., Das, I., Schweizer, M., Brown, R., Has, A. (2012): Phylogenetic relationships of the Rhacophorus everetti-group and implications for the evolution of reproductive modes in Philautus (Amphibia: Anura: Rhacophoridae). Zoologica Scripta, 41 (1), 29–46.
 
Haas, A., Wolter, J., Hertwig, S.T., Das, I. (2009): Larval morphologies of three species of stream toads, genus Ansonia (Amphibia: Bufonidae) from East Malaysia (Borneo), with a key to known Bornean Ansonia tadpoles. Zootaxa, 2302: 1–18.
 
Haas, A., Hertwig, S. and Das, I. (2006): Extreme tadpoles: The morphology of the fossorial megophryid larva, Leptobrachella mjobergi. Zoology 109(1), 26-42.