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Individual trophic specialisation and niche segregation explain the contrasting population trends of two sympatric otariids

机译：个体的营养专长和生态位隔离解释了两种同胞OTARIIDS种群趋势的对比

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摘要

Individual specialisation is increasingly recognised to be an ecological and evolutionary process having important consequences for population dynamics of vertebrates. The South American fur seal (SAFS) and the South American sea lion (SASL) are two otariid species with similar ecology that coexist in sympatry in the Uruguayan coast. These two species have contrasting trends and widely different population sizes. The underlying reasons for these population trends, unique in their geographical ranges, remain unknown. We studied the foraging ecology of these otariid species over 2 years at the individual- and population levels using the isotopic ratios (δ~(13)C-δ~(15)N) in whiskers of both sexes. We compared the isotope ratios between species and sexes and used several metrics to characterise the degree of overlap and distinctiveness in the use of isotopic niche space at the individual- and population levels. Interspecific trophic niche overlap was minimal, thus ruling out interspecific competition as the cause for the contrasting population trends of both species. At the intraspecific level, both species had sexual segregation in their foraging areas, but each species had a large overlap in the isotopic niches between sexes. While SAFS had a wider niche and generalist individuals, SASL had the narrower niche with a higher degree of individual specialisation. Behavioural constraints during the breeding season, intraspecific competition and a major dependence on resources of the Uruguayan coastal shelf may explain why SASL had a higher trophic individual specialisation and a larger vulnerability in a heavily exploited habitat by fisheries and, by consequence, a locally declining population trend.
机译：个体专业化已被越来越多地认为是对脊椎动物种群动态具有重要影响的生态和进化过程。南美海狗（SAFS）和南美海狮（SASL）是两种乌塔里科物种，具有相似的生态，共存于乌拉圭海岸。这两个物种的趋势相反，种群规模也大不相同。这些人口趋势的根本原因（在其地理范围内是唯一的）仍然未知。我们使用男女胡须中的同位素比（δ〜（13）C-δ〜（15）N）研究了这些otariid物种在2年内在个体和种群水平上的觅食生态。我们比较了物种和性别之间的同位素比率，并使用了几个指标来表征在个体和种群水平上利用同位素生态位空间的重叠程度和独特性。种间营养位的重叠很小，因此排除种间竞争是两种物种种群趋向相反的原因。在种内水平上，两个物种在其觅食区都存在性别隔离，但每个物种在性别之间的同位素生态位上有很大的重叠。 SAFS的利基市场和通才分子较广泛，而SASL的利基市场较窄，个体专业化程度较高。繁殖季节的行为限制，种内竞争以及对乌拉圭沿海陆架资源的主要依赖可能可以解释为什么SASL在营养丰富的栖息地中具有较高的营养个体专长和较大的脆弱性，因此当地人口减少趋势。

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  • 来源
    《Marine biology》 |2014年第3期|609-618|共10页
  • 作者

    Valentina Franco-Trecu; David Aurioles-Gamboa; Pablo Inchausti;

  • 作者单位

    Proyecto Pinnipedos, Seccion Etologia, Facultad de Ciencias, Universidad de la Republica, Igua 4225, 11400 Montevideo, Uruguay;

    Laboratorio de Ecologia de Pinnipedos Burney J. Le Boeuf, Centra Interdisciplinario de Ciencias Marinas, Instituto Politecnico Nacional, Ave IPN s, CP 23096, La Paz, Baja California Sur, Mexico;

    Departamento de Ecologia y Evolucion, Centro Universitario Regional Este (CURE), Universidad de la Republica, Tacuarembo S/N, 20000 Maldonado, Uruguay;

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