Meeting Abstract
Southeast-Asian Irrawaddy dolphins (Orcaella brevirostris) are highly susceptible to anthropogenic effects that reduce effective population size and genetic diversity. Coastal populations are currently listed as “Vulnerable” on IUCN’s Red List, while some riverine populations are listed as “Critically Endangered”. Though conservation efforts in developing countries have improved with abundance, habitat, and range data, additional genetic information will best inform management. Comparison of variation at adaptive immune system loci (Major Histocompatibility Complex, MHC) and neutral loci allows us to assess the severity of population bottlenecks. Irrawaddy dolphins (n=23) from the Gulf of Thailand were sequenced at the MHCIIDQB locus and just one allele was found in this population. In comparison, one allele was also found in Mekong Irrawaddy dolphins (n=37). This severe bottleneck in coastal populations is concerning, as riverine populations of O. brevirostris are hypothesized to have even lower MHC diversity due to intense anthropogenic pressures in a more confined habitat. Even in comparison to the low MHC diversity in endangered dolphin populations (e.g. Sousa chinensis and Phocoena sinus) residing in anthropogenically impacted habitats, no variation in a usually highly polymorphic locus is very uncommon and suggests low potential for O. brevirostris populations to adapt to novel pathogens. Preserving the diversity of essential functional loci in O. brevirostris should therefore be a top priority for conservation managers.
