Dear list, The latest paper on the influence of foraging behaviour on population structure of Australian sea lions is now available in Animal Behaviour:
Lowther, A.D., Harcourt, R.G., Goldsworthy, S.D., Stow, A. (2012). Population structure of adult female Australian sea lions is driven by fine-scale foraging site fidelity. Animal Behaviour doi:10.1016/j.anbehav.2011.12.015 ABSTRACT: The Australian sea lion (Neophoca cinerea) is one of the rarest otariids in the world and is notable for an asynchronous, aseasonal breeding chronology. Determining the ecological features that shape the genetic structure of marine predators such as Australian sea lions is challenging because their demersal foraging habitat is difficult to observe and quantify. Recent development in stable isotope screening techniques using milk-dependent pups as proxies for maternal isotope signatures identified temporally stable, alternate (inshore and offshore) foraging ecotypes in adult female Australian sea lions. We combine this technique with mitochondrial DNA (mtDNA) analysis of samples of 40-60% of all pups produced at seventeen of the largest South Australian colonies to determine if ecological specialisation in foraging ecotype within and between colonies has shaped maternal population structure within the species. Genetic isolation by distance was apparent at very fine geographic scales (>40km) with three distinct clusters of colonies that share multiple haplotypes being interspersed with isolated breeding sites. There was no congruence between mtDNA haplotype distribution and foraging ecotypes suggesting that observed behavioural specialisation was not maintained along matrilines. We propose that foraging specialisation within discrete fine-scale foraging areas and habitats at the individual level limits the dispersive capacity of individual adult female Australian sea lions which in turn drives population structure. Given the vulnerability of this species to extant anthropogenic impacts and given the high degree of female population structure, determining the extent of male-mediated gene-flow in this species is critical. Only then can breeding colony connectivity be established and appropriate management units identified for the species. Andrew Lowther Senior Research Officer (Pinniped Ecology) Threatened, Endangered & Protected Species (TEPS) South Australian Research & Development Institute (SARDI) - Aquatic Sciences 2 Hamra Avenue West Beach SA 5024 AUSTRALIA
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