Foraging niche variation within a species can contribute to the maintenance of phenotypic diversity. The multiniche model posits that phenotypes occupying different niches can contribute to the maintenance of balanced polymorphisms. Using coastal populations of black bears (Ursus americanus kermodei) from British Columbia, Canada, we examined potential foraging niche divergence between phenotypes (black and white “Spirit” coat color) and between genotypes (black-coated homozygote and heterozygous). We applied the Bayesian multivariate models, with biotracers of diet (δ¹³C and δ¹⁵N) together comprising the response variable, to draw inference about foraging niche variation. Variance–covariance matrices from multivariate linear mixed-effect models were visualized as the Bayesian standard ellipses in δ¹³C and δ¹⁵N isotopic space to assess potential seasonal and annual niche variation between phenotypes and genotypes. We did not detect a difference in annual isotopic foraging niche area in comparisons between genotypes or phenotypes. Consistent with previous field experimental and isotopic analyses, however, we found that white phenotype Spirit bears were modestly more enriched in δ¹⁵N during the fall foraging season, though with our modest sample sizes these results were not significant. Although also not statistically significant, variation in isotopic niches between genotypes revealed that heterozygotes were moderately more enriched in δ¹³C along hair segments grown during fall foraging compared with black-coated homozygotes. To the extent to which the pattern of elevated δ¹⁵N and δ¹³C may signal the consumption of salmon (Oncorhynchus spp.), as well as the influence of salmon consumption on reproductive fitness, these results suggest that black-coated heterozygotes could have a minor selective advantage in the fall compared with black-coated homozygotes. More broadly, our multivariate approach, coupled with knowledge of genetic variation underlying a polymorphic trait, provides new insight into the potential role of a multiniche mechanism in maintaining this rare morph of conservation priority in Canada's Great Bear Rainforest and could offer new understanding into polymorphisms in other systems.

中文翻译：

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灵熊种群内觅食生态位的表型和基因型差异

一个物种内的觅食生态位变化有助于维持表型多样性。多生态位模型假设占据不同生态位的表型有助于维持平衡的多态性。我们利用来自加拿大不列颠哥伦比亚省的沿海黑熊（Ursus americanus kermodei）种群，研究了表型（黑白“精神”毛色）和基因型（黑色毛纯合子和杂合子）之间潜在的觅食生态位差异。我们应用贝叶斯多元模型，将饮食生物示踪剂（δ ¹³ C 和 δ ¹⁵ N）一起构成响应变量，以推断觅食生态位的变化。多元线性混合效应模型的方差-协方差矩阵可视化为 δ ¹³ C 和 δ ¹⁵ N 同位素空间中的贝叶斯标准椭圆，以评估表型和基因型之间潜在的季节性和年度生态位变化。在基因型或表型之间的比较中，我们没有检测到年度同位素觅食生态位面积的差异。然而，与之前的现场实验和同位素分析一致，我们发现白色表型精神熊在秋季觅食季节期间δ ¹⁵ N略有增加，尽管我们的样本量不大，但这些结果并不显着。尽管在统计上也不显着，但基因型之间同位素生态位的变化表明，与黑色涂层纯合子相比，杂合子在秋季觅食期间生长的毛发片段中δ ¹³ C适度富集。在某种程度上，δ ¹⁵ N 和 δ ^{13 C 升高的模式可能预示着鲑鱼（} Oncorhynchus spp.）的食用，以及鲑鱼食用对繁殖适应性的影响，这些结果表明，黑衣杂合子可能具有与黑色涂层纯合子相比，秋季的选择性优势较小。更广泛地说，我们的多变量方法，加上对多态性状背后的遗传变异的了解，为多生态位机制在维持加拿大大熊雨林这种罕见的保护优先形态方面的潜在作用提供了新的见解，并可以为多态性提供新的理解。其他系统。