Geographical, temporal variability and sexual size dimorphism of mandible in cave lion (Panthera spelaea) across Northern Eurasia

The mandible size variability including sexual size dimorphism (SSD) of the cave lion (Panthera spelaea) in the Pleistocene of Northern Eurasia time has been studied basing on the univariate and multivariate statistical analyses of 76 specimens from 43 localities. It has been confirmed that SSD in adult P. spelaea, as well as in extant P. leo, is the dominant form of group variability of mandible and, to somewhat lesser extent, of variability of cheek teeth. The lowest degree of SSD has been found in a relatively small Beringian subspecies, P. spelaea vereshchagini. The geographical variability of the cave lion from Western to Eastern Eurasia was not a cline at least in the Late Pleistocene. Our results confirm a decrease in overall mandible size from the Middle Pleistocene to the Late Pleistocene over a large part of the species’ range. We speculate that evolutionary changes in mandible size, lower canines or cheek teeth may have proceeded at different rates, allometry and probable heterochrony. Our results have added a new evidence to support the subspecies status of the Beringian lion (P. spelaea vereshchagini), but they are insufficient for other decisions on cave lion taxonomy at the subspecies level.

本研究针对欧亚大陆北部更新世时期洞狮（Panthera spelaea）的下颌骨尺寸变异（包含性别体型二态性，sexual size dimorphism，以下简称SSD），基于43个化石产地的76件标本开展单变量与多变量统计分析。研究证实，成年洞狮与现生狮（Panthera leo）的SSD均为下颌骨群体变异的主导形式，对颊齿变异的影响程度相对偏弱。在体型相对小巧的白令海洞狮亚种（Panthera spelaea vereshchagini）中，SSD的分化程度最低。至少在晚更新世阶段，洞狮从西欧亚至东亚的地理分布变异并未呈现渐变群特征。本研究结果证实，在该物种分布范围的绝大多数区域内，下颌骨整体尺寸从中更新世到晚更新世呈逐渐减小的趋势。我们推测，下颌骨、下犬齿或颊齿的演化变化可能以不同速率推进，且存在异速生长（allometry）及潜在的异时性（heterochrony）现象。本研究结果为支持白令海洞狮（Panthera spelaea vereshchagini）的亚种分类地位提供了新的实证依据，但仍不足以对洞狮亚种层级的其他分类学问题作出判定。