Australian sperm whales from different whaling stocks belong to the same population

Abstract

Understanding the factors driving population structure in marine mammals is needed to evaluate the impacts of previous exploitation, current anthropogenic threats, conservation status, and success of population recovery efforts. Sperm whales are characterized by a worldwide distribution, low genetic diversity, complex patterns of social and genetic structure that differ significantly within and between ocean basins, and a long history of being commercially whaled. In Australia, sperm whales from the (International Whaling Commission assigned) southern hemisphere ‘Division 5’ stock were very heavily exploited by whaling. The present study assessed the potential effects of whaling on the genetic diversity of sperm whales in Australia and the population genetic structure of these whales within a global context. A combination of historical and contemporary sperm whale samples (n = 157) were analysed across six regions, from south‐eastern Australia (‘Division 6’ stock in the Pacific Ocean) to south‐western Australia (‘Division 5’ stock in the Indian Ocean). Sperm whales sampled from the ‘Division 5’ and ‘Division 6’ stocks belong to the same population based on nuclear and mitochondrial DNA (mtDNA) analyses. Four novel sperm whale mtDNA haplotypes were identified in animals from Australian waters. Levels of genetic diversity were low in Australian sperm whales but were similar to those previously reported for populations in the Indian and Pacific Oceans. Given the genetic distinctiveness of sperm whales in Australian waters from other regions in the Pacific and Indian Oceans, and the lack of recovery in population numbers, further scientific studies are needed to increase our understanding of population dynamics and the effectiveness of threat management strategies in this species.

Long distance runners in the marine realm: New insights into genetic diversity, kin relationships and social fidelity of Indian Ocean male sperm whales

“…SW_K1 matched the haplotype 10 defined by [45] found off South Australia and Victoria, and SW_K2 corresponded to the haplotype GG [36], exclusively found in the Indian Ocean in the Seychelles. SW_C corresponds to haplotype B [36, 45], found in Australia (Figure 2).…”

“…This fragment overlapped fully with the data from [60] and partially (602bp in common) with the sequences determined by [36]. It also overlapped fully with the 283bp fragment and partially with the 563bp fragment (514bp in common) determined by [45]. A new dataset that included all these sequences was constructed to allow a large-scale comparison between mitochondrial haplotypes.…”

“…The number of adult male sperm whales sampled off Mauritius is relatively low (n=13), but it is nevertheless notable that their mtDNA haplotypes are frequent in different regions of the Indian Ocean neighbouring Mauritius. In contrast, sperm whales sampled in the Crozet/Kerguelen (n=8) have haplotypes found in a much broader area covering all the north of the Indian Ocean, from west to east (this study, [36, 45]). This is reflected by significant or near so Φ ST and F ST values between Mauritian and Crozet/Kerguelen males.…”

“…Two others had the same haplotype (SW_MCK1) as Claire, the sole adult female of the Irene’s social group with a different MCR haplotype [21], corresponding to the haplotype N.001.001 mainly found in the Seychelles, in the Coco Islands and in the south west Australia by [36]. Another adult male had the haplotype MCK2 (differing from SW_MCK1 at position 609, table S4), one had the haplotype SW_M3 corresponding to the haplotype KK found almost exclusively in the Indian Ocean off Sri Lanka [36] and off Albany in Australia [45]. Seven males shared the haplotype SW_MC, identical to the haplotype A.001.001, common in the Indian Ocean (Figure 2).…”

Long Distance Runners in the Marine Realm: New Insights Into Genetic Diversity, Kin Relationships and Social Fidelity of Indian Ocean Male Sperm Whales

“…This fragment overlapped fully with the data from Morin et al (2018) and partially (602 bp in common) with the sequences determined by Alexander et al (2016). It also overlapped fully with the 283 bp fragment and partially with the 563 bp fragment (514 bp in common) determined by Day et al (2021). A new dataset that included all these sequences was constructed to allow a large-scale comparison between mitochondrial haplotypes.…”