Demographic collapse and low genetic diversity of the Irrawaddy dolphin population inhabiting the Mekong River

Krützen, Michael, Beasley, Isabel, Ackermann, Corinne Y., Lieckfeldt, Dietmar, Ludwig, Arne, Ryan, Gerard E., Bejder, Lars, Parra, Guido J., Wolfensberger, Rebekka, and Spencer, Peter B.S. (2018) Demographic collapse and low genetic diversity of the Irrawaddy dolphin population inhabiting the Mekong River. PLoS One, 13 (1). e0189200.

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Abstract

In threatened wildlife populations, it is important to determine whether observed low genetic diversity may be due to recent anthropogenic pressure or the consequence of historic events. Historical size of the Irrawaddy dolphin (Orcaella brevirostris) population inhabiting the Mekong River is unknown and there is significant concern for long-term survival of the remaining population as a result of low abundance, slow reproduction rate, high neonatal mortality, and continuing anthropogenic threats. We investigated population structure and reconstructed the demographic history based on 60 Irrawaddy dolphins samples collected between 2001 and 2009. The phylogenetic analysis indicated reciprocal monophyly of Mekong River Orcaella haplotypes with respect to haplotypes from other populations, suggesting long-standing isolation of the Mekong dolphin population from other Orcaella populations. We found that at least 85% of all individuals in the two main study areas: Kratie and Stung Treng, bore the same mitochondrial haplotype. Out of the 21 microsatellite loci tested, only ten were polymorphic and exhibited very low levels of genetic diversity. Both individual and frequency-based approaches suggest very low and non-significant genetic differentiation of the Mekong dolphin population. Evidence for recent bottlenecks was equivocal. Some results suggested a recent exponential decline in the Mekong dolphin population, with the current size being only 5.2% of the ancestral population. In order for the Mekong dolphin population to have any potential for long-term survival, it is imperative that management priorities focus on preventing any further population fragmentation or genetic loss, reducing or eliminating anthropogenic threats, and promoting connectivity between all subpopulations.

Item ID: 52393
Item Type: Article (Research - C1)
ISSN: 1932-6203
Copyright Information: © 2018 Krützen et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funders: WWF - Greater Mekong Program, WCS - Cambodia Program, Mekong Dolphin Conservation Project, Ocean Park Conservation Foundation Hong Kong, Mekong River Commission Environment program, Rufford Foundation Small Grants Program, Society for Marine Mammalogy Small Grants Program, IUCN Mekong Wetlands Biodiversity Project, James Cook University (JCU), Wildlife Conservation Society Research Fellowship Program, WWF Germany
Date Deposited: 07 Feb 2018 07:31
FoR Codes: 06 BIOLOGICAL SCIENCES > 0608 Zoology > 060806 Animal Physiological Ecology @ 100%
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