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Large-scale molecular diet analysis in a generalist marine mammal reveals male preference for prey of conservation concern.

ABSTRACT: Sex-specific diet information is important in the determination of predator impacts on prey populations. Unfortunately, the diet of males and females can be difficult to describe, particularly when they are marine predators. We combined two molecular techniques to describe haul-out use and prey preferences of male and female harbor seals (Phoca vitulina) from Comox and Cowichan Bay (Canada) during 2012-2013. DNA metabarcoding quantified the diet proportions comprised of prey species in harbor seal scat, and qPCR determined the sex of the individual that deposited each scat. Using 287 female and 260 male samples, we compared the monthly sex ratio with GLMs and analyzed prey consumption relative to sex, season, site, and year with PERMANOVA. The sex ratio between monthly samples differed widely in both years (range = 12%-79% males) and showed different patterns at each haul-out site. Male and female diet differed across both years and sites: Females consumed a high proportion of demersal fish species while males consumed more salmonid species. Diet composition was related to both sex and season (PERMANOVA: R 2 = 27%, p < 0.001; R 2 = 24%, p < 0.001, respectively) and their interaction (PERMANOVA: R 2 = 11%, p < 0.001). Diet differences between males and females were consistent across site and year, suggesting fundamental foraging differences, including that males may have a larger impact on salmonids than females. Our novel combination of techniques allowed for both prey taxonomic and spatiotemporal resolution unprecedented in marine predators.

SUBMITTER: Schwarz D

PROVIDER: S-EPMC6202700 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature

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Large-scale molecular diet analysis in a generalist marine mammal reveals male preference for prey of conservation concern.

Schwarz Dietmar D Spitzer Sara M SM Thomas Austen C AC Kohnert Christa M CM Keates Theresa R TR Acevedo-Gutiérrez Alejandro A

Ecology and evolution 20180915 19

Sex-specific diet information is important in the determination of predator impacts on prey populations. Unfortunately, the diet of males and females can be difficult to describe, particularly when they are marine predators. We combined two molecular techniques to describe haul-out use and prey preferences of male and female harbor seals (<i>Phoca vitulina</i>) from Comox and Cowichan Bay (Canada) during 2012-2013. DNA metabarcoding quantified the diet proportions comprised of prey species in ha ...[more]

PMID: 30386584

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Project description:BackgroundThe impact of predator-prey interactions on the evolution of many marine invertebrates is poorly understood. Since barriers to genetic exchange are less obvious in the marine realm than in terrestrial or freshwater systems, non-allopatric divergence may play a fundamental role in the generation of biodiversity. In this context, shifts between major prey types could constitute important factors explaining the biodiversity of marine taxa, particularly in groups with highly specialized diets. However, the scarcity of marine specialized consumers for which reliable phylogenies exist hampers attempts to test the role of trophic specialization in evolution. In this study, RNA-Seq data is used to produce a phylogeny of Cladobranchia, a group of marine invertebrates that feed on a diverse array of prey taxa but mostly specialize on cnidarians. The broad range of prey type preferences allegedly present in two major groups within Cladobranchia suggest that prey type shifts are relatively common over evolutionary timescales.ResultsIn the present study, we generated a well-supported phylogeny of the major lineages within Cladobranchia using RNA-Seq data, and used ancestral state reconstruction analyses to better understand the evolution of prey preference. These analyses answered several fundamental questions regarding the evolutionary relationships within Cladobranchia, including support for a clade of species from Arminidae as sister to Tritoniidae (which both preferentially prey on Octocorallia). Ancestral state reconstruction analyses supported a cladobranchian ancestor with a preference for Hydrozoa and show that the few transitions identified only occur from lineages that prey on Hydrozoa to those that feed on other types of prey.ConclusionsThere is strong phylogenetic correlation with prey preference within Cladobranchia, suggesting that prey type specialization within this group has inertia. Shifts between different types of prey have occurred rarely throughout the evolution of Cladobranchia, indicating that this may not have been an important driver of the diversity within this group.

Project description:Integrating welfare principles into conservation strategy is an emerging synthesis that encourages consideration of individual animals' quality of life in research, policies and law. However, these principles have gained limited traction in marine compared to terrestrial animal conservation. This manuscript investigates several factors that may be contributing to this disparity. In order to gauge current understanding of animal welfare science principles by marine mammal researchers and other stakeholders, a "Welfare in the Wild" workshop was convened at the 32nd European Cetacean Society conference (La Spezia, Italy, April 2018). The workshop was attended by 30 participants who completed pre- and post-workshop surveys on animal welfare principles. The survey results highlight a range of different views about exactly what animal welfare science is and how it can be applied to marine mammals. Specifically, participants' definitions appeared to vary depending on the type of employment or research they engaged in, indicating a need for an interdisciplinary common language. Secondly, we analysed the peer-reviewed literature in order to ascertain where marine mammal publications exploring welfare were being published. From 1950 to July 2020, a total of 299 articles featured both marine mammal taxa (one or more) and the word welfare in the title, abstract or keywords. This represents just 0.96% of the total peer-reviewed published papers on marine mammal taxa (n = 31,221) during the same period. When examining articles published within "Welfare and Ethics" (n = 6133) and "Aquatic-focused" (n = 139,352) journals, just 1.2% (n = 71) and 0.04% (n = 57) of articles, respectively, featured the word welfare when examining marine mammals. With the aim of exploring how explicitly including welfare evaluations in marine mammal research and management can benefit conservation outcomes, we framed our workshop and quantitative literature review findings to provide practical solutions to the language, translation and reception issues of this burgeoning cross-disciplinary collaboration.

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Large-scale molecular diet analysis in a generalist marine mammal reveals male preference for prey of conservation concern.

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Large-scale molecular diet analysis in a generalist marine mammal reveals male preference for prey of conservation concern.

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