Global Diversity in Mammalian Life Histories: Environmental Realms and Evolutionary Adaptations

Mammalian life history strategies can be characterized by a few axes of variation, which conform a space where species are positioned according to which life history strategies are favoured in the environment they exploit. Yet, we still lack global descriptions of the diversity of realized mammalian life history and of how this diversity is shaped by the environment. We used six life history traits to build a global life history space and explored how major environmental realms (land, air, water) influence mammalian life history strategies. We demonstrate that realms are tightly linked to distinct life history strategies. Predominantly, aquatic and aerial species adhere to slower life history strategies, while terrestrial species tend to exhibit faster life histories. Highly encephalized terrestrial species are a notable exception to these patterns. In addition, species transitioning between the terrestrial and aquatic realms, such as seals, show intermediate life history strategies. Further, different mode-of-life may play a significant role in allowing to expand the set of strategies exploitable in the terrestrial realm. Our results provide compelling evidence of the link between environmental realms and the diversity of life history strategies among mammals. Statement of authorshipP.C.L., R.S-G., and C.P.C. conceived the core ideas behind this paper, all authors provided fundamental inputs for its final development. E.B collected all data and performed the literature search needed to sort species in environmental realms. E.B. analysed the data with fundamental inputs from C.P.C., P.C.L, and R.G-S. All authors contributed to interpretation of the results. E.B. and C.P.C. led the writing of the manuscript which was edited by all authors.