Dobson F Stephen, Wigginton John D
Department of Zoology & Wildlife Science, Auburn University, 36849, Auburn, AL, USA.
Oecologia. 1996 Dec;108(4):610-616. doi: 10.1007/BF00329033.
Sexual size dimorphism might be influenced by environmental constraints on sexual selection or by intraspecific competition between males and females. We studied bobcats (Lynx rufus) in collections of museum specimens from western North America to examine these hypotheses. Structural body size was estimated from several measurements of the skull, ln-transformed and indexed through principal components analysis. Sexual dimorphism in body size was estimated from the difference in size index of males and females, and compared to geographic and climatic variables associated with biotic provinces (ecoregions). Of several climatic variables that were associated with bobcat body size, only seasonality of climate was associated with sexual dimorphism. Sexual size dimorphism, longitude, elevation, and seasonality were intercorrelated. As longitude decreased (moving inland from west-coastal ecoregions), sexual dimorphism decreased with the increased elevation and seasonality of continental climates of the Rocky Mountains. We suggest that increased seasonality and the need for fasting endurance by females may place constraints on the degree of sexual dimorphism in bobcats. Sexual dimorphism of body size and sexual size dimorphism of trophic structures (teeth) exhibited a strong positive association over geography, thus indirectly supporting the hypothesis that intrasexual competition for prey could account for the geographic variation in sexual size dimorphism. Thus, both environmental constraints on sexual selection of body size and intersexual competition were supported as possible explanations of the degree of sexual size dimorphism that occurs in populations of bobcats.
两性体型差异可能受到性选择的环境限制或雌雄个体间种内竞争的影响。我们研究了来自北美西部博物馆标本收藏中的短尾猫（猞猁属），以检验这些假设。通过对头骨的多项测量来估计身体结构大小，进行自然对数转换并通过主成分分析进行指数化。根据雄性和雌性大小指数的差异来估计体型上的两性差异，并与与生物区（生态区）相关的地理和气候变量进行比较。在与短尾猫体型相关的几个气候变量中，只有气候的季节性与两性差异相关。两性体型差异、经度、海拔和季节性相互关联。随着经度降低（从西海岸生态区向内陆移动），两性差异随着落基山脉大陆性气候海拔的升高和季节性增强而减小。我们认为，季节性增强以及雌性对禁食耐力的需求可能会对短尾猫两性体型差异的程度产生限制。体型的两性差异和营养结构（牙齿）的两性体型差异在地理上呈现出强烈的正相关，从而间接支持了种内对猎物的竞争可以解释两性体型差异地理变化的假设。因此，对体型性选择的环境限制和两性间竞争都被认为是短尾猫种群中两性体型差异程度的可能解释。
