Body size reflects realized physiological niche width at the population level and provides insights into the potential resiliency of a species to natural and anthropogenic perturbations to ecosystems. We analyzed patterns of American black and brown bear body size through a meta‐analysis of data from 18 studies conducted across North America, to evaluate the effects of species, sex, latitude, sympatry, and harvest. We used a bootstrap model selection procedure, which accounted for differences in sample size and population variation between studies, to investigate patterns in body mass. As expected, we found that brown bears were generally larger than black bears and both species were sexually dimorphic (i.e., males were generally larger than females). Black bear body size was not related to latitude, whereas brown bear body size was greatest at intermediate latitudes, possibly due to the presence of salmon. Neither sympatry nor harvest was associated with body size for either species at the geographic scale of our meta‐analyses, but both may warrant consideration at the local scale. Body size, as an index of population health, reflects phenotypic plasticity within species and populations and may serve as a useful indicator of niche utilization. Indeed, understanding large‐scale physiological patterns such as these can assist in understanding past, present, and future changes to realized niches and subsequent resiliency of species and populations.

中文翻译：

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北美黑熊和棕熊的体型可塑性

体长反映了种群水平上已实现的生理生态位宽度，并提供了对物种对自然和人为干扰生态系统的潜在适应力的见识。通过对北美18项研究的数据进行荟萃分析，我们分析了美洲黑熊和棕熊体型的模式，以评估物种，性别，纬度，交感和收获的影响。我们使用了引导程序模型选择程序，该程序考虑了样本之间的差异以及研究之间的总体差异，以研究体重的模式。不出所料，我们发现棕熊通常比黑熊大，并且两种物种都具有两性性（即雄性通常比雌性大）。黑熊的体型与纬度无关，而棕熊的体型在中纬度地区最大，可能是由于鲑鱼的存在。在我们的荟萃分析的地理范围内，两种物种的体型均与共生关系和收获均无关，但都可能需要在当地进行考虑。身体大小作为种群健康的一项指标，反映了物种和种群内的表型可塑性，并且可以作为利基利用的有用指标。的确，了解诸如此类的大规模生理模式可以帮助了解过去，现在和将来对已实现的生态位的变化以及物种和种群的适应能力。但两者都可能需要在当地进行考虑。身体大小作为种群健康的一项指标，反映了物种和种群内的表型可塑性，并且可以作为利基利用的有用指标。确实，了解诸如此类的大规模生理模式可以帮助您了解过去，现在和将来对已实现的生态位的变化以及物种和种群的适应能力。但两者都可能需要在当地进行考虑。身体大小作为种群健康的一项指标，反映了物种和种群内的表型可塑性，并且可以作为利基利用的有用指标。的确，了解诸如此类的大规模生理模式可以帮助了解过去，现在和将来对已实现的生态位的变化以及物种和种群的适应能力。