Riparian Evolution research by graduate student Chan Kin Onn and his collaborators investigates speciation and diversification of riparian amphibians along drainage systems in Peninsular Malaysia.


Asian cascade frogs


Cascade Frogs of the genus Amolops are a wide-ranging species that are distributed from western India and southern China, southwards through Indochina and the Malay Peninsula. These frogs are strictly riparian, occurring in the torrential zones of moderate to swift-flowing forest streams with tadpoles characterized by having gastromyzophorus adhesive disk (ventral sucker). Adults are medium to large in size and possess expanded digital disks. Their firm dependency on forest streams and rivers, makes them a unique model system to study the spatio-temporal evolution of amphibians along drainage systems.

The Amolops larutensis complex

Amolops larutensis occur in Peninsular Malaysia and presumably extreme southern Thailand. Preliminary mtDNA data indicate that this species complex is composed of at least five genetically and morphologically divergent lineages. The distribution of these lineages largely corresponds to major drainage systems and mountain ranges with the main genetic split happening on either side of the Titiwangsa mountain range. Interestingly, the mitochondrial phylogeny also showed multiple instances of haplotype mixing among populations along the east coast and a potential hybrid zone where two distinct haplotypes were found in a single population. Areas where haplotype mixing were detected also corresponded to monsoon flood basins. Using a genomic approach, Chan aims to examine the population genetic structure of the Amolops larutensis Complex to understand how riparian amphibians diversified through time and space along drainage systems and the short and long-term effects of annual monsoon flooding on the demographic structure of these riparian populations. 

Areas of endemism in Peninsular Malaysia: Biogeography and Conservation

Malaysia is regarded as one of the 17 mega-diverse countries in the world, yet its biodiversity remains largely unknown or understudied. Within the last decade, Chan and other members of an international research team have discovered and described no less than 40 new reptile and amphibian species just in Peninsular Malaysia alone, and this progression shows no sign of tapering off. A better understanding of species and distribution boundaries has led to the realization that the vast biodiversity in Peninsular Malaysia is concentrated within certain “hotspots”. Chan uses niche modeling, geospatial and phylogenetic data of endemic herpetofaunal species to define and demarcate specific areas of endemism in Peninsular Malaysia to establish a framework for future phylogeographic hypotheses testing and also aid in prioritizing target areas for conservation.