Abstract
AbstractIntraspecific variation in animal mating systems can have important implications for ecological, evolutionary and demographic processes in wild populations. For example, patterns of mating can impact social structure, dispersal, effective population size and inbreeding. However, few species have been studied in sufficient detail to elucidate mating system plasticity and its dependence on ecological and demographic factors. Southern elephant seals (Mirounga leonina) have long been regarded as a textbook example of a polygynous mating system, with dominant ‘beachmaster’ males controlling harems of up to several hundred females. However, behavioural and genetic studies have uncovered appreciable geographic variation in the strength of polygyny among elephant seal populations. We, therefore, used molecular parentage analysis to investigate patterns of parentage in a small satellite colony of elephant seals at the South Shetland Islands. We hypothesised that dominant males would be able to successfully monopolise the relatively small numbers of females present in the colony, leading to relatively high levels of polygyny. A total of 424 individuals (comprising 33 adult males, 101 adult females and 290 pups) sampled over 8 years were genotyped at 20 microsatellites and reproductive success was analysed by genetically assigning parents. Paternity could only be assigned to 31 pups (10.7%), despite our panel of genetic markers being highly informative and the genotyping error rate being very low. The strength of inferred polygyny was weak in comparison to previous genetic studies of the same species, with the most successful male fathering only seven pups over the entire course of our study. Our results show that, even in a species long regarded as a model for extreme polygyny, male reproductive skew can vary substantially among populations.
Highlights
Understanding mating systems and their evolution is a central goal of behavioural and molecular ecology, animal behaviour and evolutionary biology (Clutton-Brock, 1989; Kempenaers, 2008; Neff & Pitcher, 2005; Reynolds, 1996)
Southern elephant seals have long been regarded as an example of extreme polygyny (Clutton-Brock, 2016), with ‘beachmaster’ males monopolising large harems of breeding females (Carrick & Ingham, 1962) and fathering up to 90% of all offspring (Fabiani et al, 2004; Hoelzel et al, 1999; Wainstein et al, 1997)
We investigated patterns of parentage at a southern elephant seal breeding colony in the South Shetlands, where low densities and high rates of turnover among animals may lead to different outcomes in terms of male reproductive success
Summary
Understanding mating systems and their evolution is a central goal of behavioural and molecular ecology, animal behaviour and evolutionary biology (Clutton-Brock, 1989; Kempenaers, 2008; Neff & Pitcher, 2005; Reynolds, 1996). Mating systems influence a multitude of ecological and evolutionary processes, ranging from social structure, dispersal and gene flow through to the evolution of life-history and sexually selected traits, local adaptation and speciation (Dieckmann et al, 1999; Ross, 2001). Sexual selection for indicators of male fitness such as large body size, behavioural dominance and the control of resources results in polygynous mating systems, where the variance in reproductive success among males of the same population can be considerable (Clutton-Brock, 1988). The extent to which male reproductive success varies among species depends on ecological and phylogenetic factors
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