Elevational gradients coincide with expansive climatic gradients and diverse plant and animal communities. We evaluated the small mammal assemblages in eight distinct vegetation types across an elevational gradient in southern California, the Deep Canyon Transect, to determine how assemblage composition changes across the gradient and to identify species with similar habitat associations. Livetrapping efforts (4,800 trap-nights) yielded 1,097 captures of 713 individuals, representing 14 heteromyid and cricetid species. Heteromyids dominated the six lower-elevation vegetation types (< 1,300 m a.s.l.), whereas cricetids dominated the upper end of the gradient. Richness and diversity exhibited bimodal responses to elevation, which do not conform to mid-domain effect null predictions. Canonical correspondence analysis revealed that 75% of the variation in small mammal abundances was explainable by habitat characteristics, and cluster analysis grouped small mammals into three ecologically distinct groups based on their habitat associations. One contained only Chaetodipus penicillatus, while the others were comprised of low- and high-elevation species, respectively. The low-elevation species exhibit unusual levels of sympatry (and syntopy) among closely related species of pocket mice (Chaetodipus). Further efforts should investigate the mechanisms of coexistence for Chaetodipus species with nearly identical associations and seasonal effects on richness and diversity. Repeated surveys of entire gradients such as the Deep Canyon Transect will help refine our understanding of temporal dynamics of community assemblage and diversity.

中文翻译：

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南加州海拔梯度上的小型哺乳动物组合组成和栖息地关联

海拔梯度与广阔的气候梯度和多样化的植物和动物群落相吻合。我们评估了加利福尼亚州南部深峡谷横断面海拔梯度上八种不同植被类型中的小型哺乳动物组合，以确定组合组成如何在梯度上发生变化，并确定具有相似栖息地关联的物种。Livetraping 工作（4,800 个陷阱之夜）捕获了 713 只个体的 1,097 次，代表了 14 种异粒虫和仓鼠。Heteromyids 主导了六种低海拔植被类型 (< 1,300 m asl)，而 cricetids 主导了梯度的上端。丰富度和多样性表现出对海拔的双峰响应，这不符合中域效应无效预测。规范对应分析显示，75% 的小型哺乳动物丰度变化可以通过栖息地特征来解释，聚类分析根据栖息地关联将小型哺乳动物分为三个生态不同的组。一个只包含 Chaetodipus penicillatus，而其他分别由低海拔和高海拔物种组成。低海拔物种在密切相关的袋鼠（Chaetodipus）物种之间表现出不寻常的同情（和同位）水平。进一步的努力应该研究 Chaetodipus 物种的共存机制，它们对丰富度和多样性具有几乎相同的关联和季节性影响。对整个梯度（例如深峡谷横断面）的重复调查将有助于完善我们对群落组合和多样性的时间动态的理解。