Gorman Kristen B, Williams Tony D, Fraser William R
Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada; Polar Oceans Research Group, Sheridan, Montana, United States of America.
Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.
PLoS One. 2014 Mar 5;9(3):e90081. doi: 10.1371/journal.pone.0090081. eCollection 2014.
Sexual segregation in vertebrate foraging niche is often associated with sexual size dimorphism (SSD), i.e., ecological sexual dimorphism. Although foraging behavior of male and female seabirds can vary markedly, differences in isotopic (carbon, δ13C and nitrogen, δ15N) foraging niche are generally more pronounced within sexually dimorphic species and during phases when competition for food is greater. We examined ecological sexual dimorphism among sympatric nesting Pygoscelis penguins asking whether environmental variability is associated with differences in male and female pre-breeding foraging niche. We predicted that all Pygoscelis species would forage sex-specifically, and that higher quality winter habitat, i.e., higher or lower sea ice coverage for a given species, would be associated with a more similar foraging niche among the sexes.
P2/P8 primers reliably amplified DNA of all species. On average, male Pygoscelis penguins are structurally larger than female conspecifics. However, chinstrap penguins were more sexually dimorphic in culmen and flipper features than Adélie and gentoo penguins. Adélies and gentoos were more sexually dimorphic in body mass than chinstraps. Only male and female chinstraps and gentoos occupied separate δ15N foraging niches. Strong year effects in δ15N signatures were documented for all three species, however, only for Adélies, did yearly variation in δ15N signatures tightly correlate with winter sea ice conditions. There was no evidence that variation in sex-specific foraging niche interacted with yearly winter habitat quality.
Chinstraps were most sexually size dimorphic followed by gentoos and Adélies. Pre-breeding sex-specific foraging niche was associated with overall SSD indices across species; male chinstrap and gentoo penguins were enriched in δ15N relative to females. Our results highlight previously unknown trophic pathways that link Pygoscelis penguins with variation in Southern Ocean sea ice suggesting that each sex within a species should respond similarly in pre-breeding trophic foraging to changes in future winter habitat.
脊椎动物觅食生态位中的性别隔离通常与两性异形（SSD）相关，即生态性二态性。尽管雄性和雌性海鸟的觅食行为可能有显著差异，但在两性异形物种以及食物竞争更为激烈的阶段，同位素（碳，δ13C和氮，δ15N）觅食生态位的差异通常更为明显。我们研究了同域筑巢的阿德利企鹅属企鹅之间的生态性二态性，探讨环境变异性是否与雄性和雌性繁殖前觅食生态位的差异有关。我们预测，所有阿德利企鹅属物种都会进行性别特异性觅食，并且更高质量的冬季栖息地，即对于特定物种而言更高或更低的海冰覆盖率，将与两性之间更相似的觅食生态位相关。
P2/P8引物可靠地扩增了所有物种的DNA。平均而言，雄性阿德利企鹅属企鹅在结构上比雌性同种企鹅更大。然而，南极帽带企鹅在喙长和鳍状肢特征上的两性异形比阿德利企鹅和巴布亚企鹅更明显。阿德利企鹅和巴布亚企鹅在体重上的两性异形比南极帽带企鹅更明显。只有南极帽带企鹅和巴布亚企鹅的雄性和雌性占据了不同的δ15N觅食生态位。记录了所有三个物种在δ15N特征上强烈的年份效应，然而，只有阿德利企鹅的δ15N特征的年度变化与冬季海冰条件紧密相关。没有证据表明性别特异性觅食生态位的变化与年度冬季栖息地质量相互作用。
南极帽带企鹅的两性异形最为明显，其次是巴布亚企鹅和阿德利企鹅。繁殖前的性别特异性觅食生态位与跨物种的总体SSD指数相关；相对于雌性，雄性南极帽带企鹅和巴布亚企鹅的δ15N含量更高。我们的结果突出了以前未知的营养途径，这些途径将阿德利企鹅属企鹅与南大洋海冰的变化联系起来，表明一个物种内的每一种性别在繁殖前的营养觅食中对未来冬季栖息地的变化应该有类似的反应。
