Vietnam contains more species of reptiles and amphibians than any other country in Indochina. This stunning biodiversity is associated with an equally rich assortment of topography. A major fault zone, the Ailao Shan shear zone, divides the northern part of the country. North-south tending mountains and highlands occupy 75% of Vietnam. Several major drainage systems occur in the country, two of which receive large tributaries and open into vast deltas. The Red River in northeastern Vietnam is fed by five separate large rivers and numerous smaller tributaries. And the Mekong River, which empties in the southeastern Mekong delta, is fed by five large rivers within Vietnam and several others in Laos, Thailand, Cambodia and China.
Does this geography play a role in generating the species richness? Did insularization of groups via these drainages lead to genetic differentiation and perhaps speciation? We are probing these questions by looking for repeated patterns of genetic diversity within Vietnam and adjacent southern China. To answer these, we’ve formed an international collaboration with Dr. Nikolai Orlov, Zoological Institute of St. Petersburg, and several Chinese and Vietnamese colleagues. A major portion of this work has been the focus of the doctoral work of Andre Ngo.
Species and population level relationships of maternal lineages of a variety of Vietnamese reptiles and amphibians are being investigated using DNA sequences, and a number of potentially cryptic species have been identified.
The cascade and odorous frogs, genera Amolops, Huia and Odorrana, are tied to rivers and streams. Often species are known only from a single mountain. These peculiar ranid frogs possess broad toe pads as adults and an abdominal sucker as tadpoles to adhere to the slippery rocks in fast moving water. Their ecological specialization effectively ties these frogs to river systems and provides an opportunity to compare the patterns of maternal lineage distribution in restricted groups to those from more widely distributed groups.
The Asian black-spined toad, Bufo melanostictus, is found throughout Asia in both forested areas and urban settings. The ubiquitous nature of these toads provides the opportunity to look at the distribution patterns of maternal lineages in a wide-ranging species.
The frogs of the genus Microhyla are widespread throughout Vietnam. These minute frogs are found in abundance in a variety of habitats including primary forest, open fields, rice paddies, buffalo wallows, and roadside ditches. Three species, Microhyla heymonsi, M. ornata, and M. pulchra, even occur syntopically at several sites.
While usually recognized as a single species in Vietnam and China, the Asian tree frog, Polypedates leucomystax, is highly variable in appearance, with large, small, reddish, golden, striped, spotted, patterned and unpatterned forms commonplace. Additionally, allozyme studies have suggested that multiple species are present—an hypothesis further supported by the discovery of different advertisement calls from sympatric animals in Vietnam and our own genetic work.
Amy Lathrop initiated a study of the diversity and phylogenetic relationships of megophryid frogs. Work is also nearing completion on the genetic diversity within Vietnam. Thus far, these investigations have led to the descriptions of several new species.
In addition to amphibians, we are evaluating the evolutionary history of four genera of snakes: Oligodon, Dinodon, Lycodon and Boiga. Marc Green, a master’s student, has been heading up the molecular-based study of Oligodon. The study of Boiga is being headed up by Dr. Robin Lawson of the California Academy of Sciences. All work in Vietnam also involves researchers from the Institute of Ecology and Biological Resources.