Disentangling the Contribution of Sexual Selection and Ecology to the Evolution of Size Dimorphism in Pinnipeds

Krüger, Oliver; Wolf, Jochen B. W.; Jonker, Rudy M.; Hoffman, Joseph I.; Trillmich, Fritz

doi:10.1111/evo.12370

Cited by 53 publications

(37 citation statements)

References 66 publications

(164 reference statements)

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“…In the past, these traits made them easy targets for hunting, but today they facilitate long-term studies of known individuals. This predictability, coupled with interest in their wide range of breeding behaviors (Cassini, 2000;Fitzpatrick, Almbro, Gonzalez-Voyer, Kolm, & Simmons, 2012;Krüger, Wolf, Jonker, Hoffman, & Trillmich, 2014), demographic responses to climate change (Forcada & Hoffman, 2014), and interactions with humans (Kovacs et al, 2012), has led to the development of parallel genetic studies of many related species (Stoffel et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Heterozygosity at neutral and immune loci is not associated with neonatal mortality due to microbial infection in Antarctic fur seals

Litzke

Ottensmann

Forcada

et al. 2019

Ecology and Evolution

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Numerous studies have reported correlations between the heterozygosity of genetic markers and fitness. These heterozygosity–fitness correlations (HFCs) play a central role in evolutionary and conservation biology, yet their mechanistic basis remains open to debate. For example, fitness associations have been widely reported at both neutral and functional loci, yet few studies have directly compared the two, making it difficult to gauge the relative contributions of genome‐wide inbreeding and specific functional genes to fitness. Here, we compared the effects of neutral and immune gene heterozygosity on death from bacterial infection in Antarctic fur seal ( Arctocephalus gazella ) pups. We specifically developed a panel of 13 microsatellites from expressed immune genes and genotyped these together with 48 neutral loci in 234 individuals, comprising 39 pups that were classified at necropsy as having most likely died of bacterial infection together with a five times larger matched sample of healthy surviving pups. Identity disequilibrium quantified from the neutral markers was positive and significant, indicative of variance in inbreeding within the study population. However, multilocus heterozygosity did not differ significantly between healthy and infected pups at either class of marker, and little evidence was found for fitness associations at individual loci. These results support a previous study of Antarctic fur seals that found no effects of heterozygosity at nine neutral microsatellites on neonatal survival and thereby help to refine our understanding of how HFCs vary across the life cycle. Given that nonsignificant HFCs are underreported in the literature, we also hope that our study will contribute toward a more balanced understanding of the wider importance of this phenomenon.

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Section: Introductionmentioning

confidence: 99%

Heterozygosity at neutral and immune loci is not associated with neonatal mortality due to microbial infection in Antarctic fur seals

Litzke

Ottensmann

Forcada

et al. 2019

Ecology and Evolution

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“…The three ringed seal subspecies were added according to their separation after the last ice age 48 . Demographic and life-history data for each species were obtained from 49 . While most data stayed untransformed, we calculated sexual size dimorphism (SSD) as the ratio of male to female body mass, and log-transformed abundance across species to account for the several orders of magnitude differences in population sizes.…”

Section: Methodsmentioning

confidence: 99%

Recent demographic histories and genetic diversity across pinnipeds are shaped by anthropogenic interactions and mediated by ecology and life-history

Stoffel

Humble

Acevedo‐Whitehouse

et al. 2018

Preprint

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A central paradigm in conservation biology is that population bottlenecks reduce genetic diversity and negatively impact population viability and adaptive potential. In an era of unprecedented biodiversity loss and climate change, understanding both the determinants and consequences of bottlenecks in wild populations is therefore an increasingly important challenge. However, as most studies have focused on single species, the multitude of potential drivers and the consequences of bottlenecks remain elusive. Here, we used a comparative approach by integrating genetic data from over 11,000 individuals of 30 pinniped species with demographic, ecological and life history data to elucidate the consequences of large-scale commercial exploitation by 18 th and 19 th century sealers. We show that around one third of these species exhibit strong genetic signatures of recent population declines, with estimated bottleneck effective population sizes reflecting just a few tens of surviving individuals in the most extreme cases. Bottleneck strength was strongly associated with both breeding habitat and mating system variation, and together with global abundance explained a large proportion of the variation in genetic diversity across species. Overall, there was no relationship between bottleneck intensity and IUCN status, although three of the four most heavily bottlenecked species are currently endangered. Our study reveals an unforeseen interplay between anthropogenic exploitation, ecology, life history and demographic declines, sheds new light on the determinants of genetic diversity, and is consistent with the notion that both genetic and demographic factors influence population viability.

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“…Charnov and Downhower (1995) modeled the relationship between litter size and offspring birth mass variation and found strong support for an inverse relationship; hence we can expect large variation in offspring birth mass when litter size is small. A wealth of information is also available for pinnipeds, including ecological (Caro, Stankowich, Mesnick, Costa, & Beeman, 2012;Krüger, Wolf, Jonker, Hoffman, & Trillmich, 2014) and life history (Fitzpatrick, Almbro, Gonzalez-Voyer, Hamada, et al, 2012;Fitzpatrick, Almbro, Gonzalez-Voyer, Kolm, & Simmons, 2012;Trillmich, 1996) variables that can be used to test whether there are significant correlates of AP.…”

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confidence: 99%

Evolution of age at primiparity in pinnipeds in the absence of the quality–quantity trade‐off in reproduction

Kalberer

DeRango

Trillmich

et al. 2019

Ecology and Evolution

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Age at primiparity (AP) is a key life history trait which is crucial to the evolution of life history strategies. This trait is particularly interesting in pinnipeds (walrus, eared seals, and true seals), which are monotocous animals. Thus, the commonly observed trade‐off between offspring quality and quantity does not apply to this taxon. Therefore, comparative studies on the evolution of AP might shed light on other important evolutionary correlates when litter size is fixed. Using phylogenetic generalized least squares analyses, we found a strong negative and robust correlation between relative birth mass (mean pup birth mass as a proportion of mean adult female mass) and AP. Rather than trading‐off an early start of reproduction with light relative offspring mass, this result suggests that pinnipeds exhibit either faster (i.e., higher relative offspring mass leading to shorter lactation length, and thus shorter interbirth interval) or slower life histories and that an early AP and a heavy relative offspring mass co‐evolved into a comparatively fast life history strategy. On the other hand, AP was positively related to lactation length: A later start of reproduction was associated with a longer lactation length. Consequently, variation in AP in pinnipeds seems to be affected by an interplay between costs and benefits of early reproduction mediated by relative investment into the single offspring via relative birth mass and lactation length.

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Disentangling the Contribution of Sexual Selection and Ecology to the Evolution of Size Dimorphism in Pinnipeds

Cited by 53 publications

References 66 publications

Heterozygosity at neutral and immune loci is not associated with neonatal mortality due to microbial infection in Antarctic fur seals

Heterozygosity at neutral and immune loci is not associated with neonatal mortality due to microbial infection in Antarctic fur seals

Recent demographic histories and genetic diversity across pinnipeds are shaped by anthropogenic interactions and mediated by ecology and life-history

Evolution of age at primiparity in pinnipeds in the absence of the quality–quantity trade‐off in reproduction

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