Abstract:
A clear understanding of population structure is essential for assessing
conservation status and implementing management strategies. A small, nonmigratory
population of humpback whales in the Arabian Sea is classified as
‘‘Endangered’’ on the IUCN Red List of Threatened Species, an assessment
constrained by a lack of data, including limited understanding of its relationship to
other populations. We analysed 11 microsatellite markers and mitochondrial DNA
sequences extracted from 67 Arabian Sea humpback whale tissue samples and
compared them to equivalent datasets from the Southern Hemisphere and North
Pacific. Results show that the Arabian Sea population is highly distinct; estimates of
gene flow and divergence times suggest a Southern Indian Ocean origin but
indicate that it has been isolated for approximately 70,000 years, remarkable for a
species that is typically highly migratory. Genetic diversity values are significantly
lower than those obtained for Southern Hemisphere populations and signatures of
ancient and recent genetic bottlenecks were identified. Our findings suggest this is
the world’s most isolated humpback whale population, which, when combined with
low population abundance estimates and anthropogenic threats, raises concern for its survival. We recommend an amendment of the status of the population to
‘‘Critically Endangered’’ on the IUCN Red List.
