Data from: Rensch's rule in large herbivorous mammals derived from metabolic scaling

Rensch’s rule, which states that the magnitude of sexual size dimorphism tends to increase with increasing body size, has evolved independently in three lineages of large herbivorous mammals: bovids (antelopes), cervids (deer), and macropodids (kangaroos). This pattern can be explained by a model that combines allometry, life-history theory, and energetics. The key features are that female group size increases with increasing body size and that males have evolved under sexual selection to grow large enough to control these groups of females. The model predicts relationships among body size and female group size, male and female age at first breeding, death and growth rates, and energy allocation of males to produce body mass and weapons. Model predictions are well supported by data for these megaherbivores. The model suggests hypotheses for why some other sexually dimorphic taxa, such as primates and pinnipeds (seals and sea lions), do or do not conform to Rensh’s rule.

伦施法则（Rensch’s rule）指出，性别体型二态性的程度往往随体型增大而增强，这一规律已在三类大型草食哺乳动物的演化支中独立得到印证：牛科动物（bovids，即羚羊）、鹿科动物（cervids，即鹿）与袋鼠科（macropodids，即袋鼠）。这一演化模式可通过整合异速生长（allometry）、生活史理论（life-history theory）与能量学（energetics）的理论模型予以阐释。该模型的核心特征为：雌性群体规模随体型增大而扩张，且雄性在性选择（sexual selection）的作用下演化出足够庞大的体型，以掌控此类雌性群体。模型预测了体型与雌性群体规模、雌雄首次繁殖年龄、死亡率与生长速率，以及雄性用于体重增长与争斗器官发育的能量分配之间的关联。上述巨型草食动物（megaherbivores）的实测数据，为该模型的预测结果提供了充分支撑。该模型还为解释灵长类、鳍足类（pinnipeds，即海豹与海狮）等其他具有性别二态性的类群为何符合或不符合伦施法则提供了假说思路。