Department of Biotechnology, Chemistry, and Environmental Engineering, University of Aalborg, Aalborg, Denmark.
PLoS One. 2012;7(10):e48352. doi: 10.1371/journal.pone.0048352. Epub 2012 Oct 26.
Sexual dimorphism is widespread among carnivorans, and has been an important evolutionary factor in social ecology. However, its presence in sabertoothed felids remains contentious. Here we present a comprehensive analysis of extant Panthera and the sabertoothed felid Smilodon fatalis. S. fatalis has been reported to show little or no sexual dimorphism but to have been intraspecifically variable in skull morphology. We found that large and small specimens of S. fatalis could be assigned to male and female sexes with similar degrees of confidence as Panthera based on craniomandibular shape. P. uncia is much less craniomandibularly variable and has low levels of sexual size-dimorphism. Shape variation in S. fatalis probably reflects sexual differences. Craniomandibular size-dimorphism is lower in S. fatalis than in Panthera except P. uncia. Sexual dimorphism in felids is related to more than overall size, and S. fatalis and the four large Panthera species show marked and similar craniomandibular and dental morphometric sexual dimorphism, whereas morphometric dimorphism in P. uncia is less. Many morphometric-sexually dimorphic characters in Panthera and Smilodon are related to bite strength and presumably to killing ecology. This suggests that morphometric sexual dimorphism is an evolutionary adaptation to intraspecific resource partitioning, since large males with thicker upper canines and stronger bite forces would be able to hunt larger prey than females, which is corroborated by feeding ecology in P. leo. Sexual dimorphism indicates that S. fatalis could have been social, but it is unlikely that it lived in fusion-fission units dominated by one or a few males, as in sub-Saharan populations of P. leo. Instead, S. fatalis could have been solitary and polygynous, as most extant felids, or it may have lived in unisexual groups, as is common in P. leo persica.
性二型现象在食肉动物中普遍存在，并且一直是社会生态学中的一个重要进化因素。然而，在剑齿猫科动物中，这种现象的存在仍然存在争议。在这里，我们对现生的 Panthera 和剑齿猫科动物 Smilodon fatalis 进行了全面的分析。有报道称，S. fatalis 的性二型现象不明显，但在头骨形态上存在种内变异。我们发现，根据头骨和下颌的形状，大、小 S. fatalis 标本可以被分配为雄性和雌性，其置信度与 Panthera 相似。P. uncia 的头骨和下颌形态变化较小，性二型程度较低。S. fatalis 的形态变化可能反映了性别差异。除了 P. uncia 之外，S. fatalis 的头骨和下颌大小的性二型程度低于 Panthera。猫科动物的性二型现象不仅与体型大小有关，而且 S. fatalis 和四个大型 Panthera 物种的头骨和下颌形态和牙齿形态的性二型现象明显且相似，而 P. uncia 的形态学二型性程度较低。Panthera 和 Smilodon 中许多形态学上性二型的特征与咬合力有关，可能与捕食生态有关。这表明形态学上的性二型是一种对种内资源分配的进化适应，因为具有更厚的上犬齿和更强咬合力的大型雄性能够捕食比雌性更大的猎物，这在 P. leo 的食性中得到了证实。性二型现象表明 S. fatalis 可能是社会性的，但它不太可能像撒哈拉以南的 P. leo 种群那样，生活在由一两个或少数雄性主导的融合-裂变单位中。相反，S. fatalis 可能是独居和多配偶制的，就像大多数现生猫科动物一样，或者它可能生活在单性群体中，就像 P. leo persica 中常见的那样。
