Data from: Body size and extinction risk in terrestrial mammals above the species level

Mammalian body mass strongly correlates with life history and population properties at the scale of mouse to elephant. Large body size is thus often associated with elevated extinction risk. I examined the North American fossil record (28–1 million years ago) of 276 terrestrial genera to uncover the relationship between body size and extinction probability above the species level. Phylogenetic comparative analysis revealed no correlation between sampling-adjusted durations and body masses ranging 7 orders of magnitude, an observation that was corroborated by survival analysis. Most of the ecological and temporal groups within the data set showed the same lack of relationship. Size-biased generic extinctions do not constitute a general feature of the Holarctic mammalian faunas in the Neogene. Rather, accelerated loss of large mammals occurred during intervals that experienced combinations of regional aridification and increased biomic heterogeneity within continents. The latter phenomenon is consistent with the macroecological prediction that large geographic ranges are critical to the survival of large mammals in evolutionary time. The frequent lack of size selectivity in generic extinctions can be reconciled with size-biased species loss if extinctions of large and small mammals at the species level are often driven by ecological perturbations of different spatial and temporal scales, while those at the genus level are more synchronized in time as a result of fundamental, multiscale environmental shifts.

哺乳动物体型质量（mammalian body mass）与从小鼠到大象的类群尺度下的生活史（life history）及种群特征存在强相关性。体型较大的类群通常伴随更高的灭绝风险。本研究基于276个陆生属（terrestrial genera，genus的复数形式）的北美化石记录（2800万至100万年前），旨在揭示物种以上分类阶元内体型大小与灭绝概率之间的关联。系统发育比较分析（phylogenetic comparative analysis）结果显示，经采样校正的类群存续时长（sampling-adjusted durations）与跨度达7个数量级（7 orders of magnitude）的体型质量之间并无相关性，该观测结果亦得到生存分析（survival analysis）的验证。数据集内的多数生态分组与时间分组均呈现出相同的无相关性特征。体型偏好性的属级灭绝（Size-biased generic extinctions）并非新近纪（Neogene）全北区（Holarctic）哺乳动物群的普遍特征。与之相反，大型哺乳动物的加速消亡发生在区域干旱化（regional aridification）与大陆内部生物群区异质性（biomic heterogeneity）提升的重叠时段。该现象契合宏生态学（macroecology）的预测：广阔的地理分布范围对于大型哺乳动物在演化时间尺度上的存续至关重要。若物种水平上的大、小型哺乳动物灭绝往往由不同时空尺度的生态扰动（ecological perturbations）驱动，而属级灭绝则因根本性的多尺度环境变化（multiscale environmental shifts）而在时间上更为同步，那么属级灭绝频繁缺乏体型选择性的现象，便可与体型偏好性的物种灭绝现象相协调。