Anthropogenic impacts on threatened species erode functional diversity in chelonians and crocodilians

Abstract

The Anthropocene is tightly associated with a drastic loss of species worldwide and the disappearance of their key ecosystem functions. The orders Testudines (turtles and tortoises) and Crocodilia (crocodiles, alligators, and gharials) contain numerous threatened, long-lived species for which the functional diversity and potential erosion by anthropogenic impacts remains unknown. Here, we examine 259 (69%) of the existing 375 species of Testudines and Crocodilia, quantifying their life history strategies (i.e., trade-offs in survival, development, and reproduction) from open-access data on demography, ancestry, and threats. We find that the loss of functional diversity in simulated extinction scenarios of threatened species is greater than expected by chance. Moreover, the effects of unsustainable local consumption, diseases, and pollution are associated with life history strategies. In contrast, climate change, habitat disturbance, and global trade affect species independent of their life history strategy. Importantly, the loss of functional diversity for threatened species by habitat degradation is twice that for all other threats. Our findings highlight the importance of conservation programmes focused on preserving the functional diversity of life history strategies jointly with the phylogenetic representativity of these highly threatened groups.

Severe fire regimes decrease resilience of ectothermic populations

“…We also estimated other life history traits from these IPMs, but we decided to focus our analyses on generation time and net reproductive output only, as they describe the principal axes of the life history variation in our species (Figs. S8-S9), as well as in other reptiles (Rodriguez-Caro et al . 2023).…”

A slow-fast trait continuum at the whole community level in relation to land-use intensification

“…However, while there is theoretical and empirical support for a community-level slow-fast trait response, conflicting observations challenge this hypothesis. First, while the slow-fast spectrum is well defined in plants, additional axes of variation in functional and life-history strategies (e.g., reproductive strategies, and their defining traits such as the timing of reproductive onset and reproductive allocation) have been identified in both plants and other organisms 29 , 30 , and these may respond to different drivers and dominate the distribution of certain organismal groups, decoupling them from the response of others 3 , 31 . Furthermore, guilds might vary in their strength of response to the drivers of the slow-fast functional axis 32 and could respond over different spatiotemporal scales 33 leading to weak overall coupling.…”

Island biodiversity in peril: Anticipating a loss of mammals' functional diversity with future species extinctions

“…Many threatened species are functionally unique, with uncommon trait combinations (Carmona et al., 2021; Matthews et al., 2022), and some studies have demonstrated that the most endangered species tend to be large and long‐lived, with few offspring and small geographic ranges (e.g., Carmona et al., 2021). At a global scale, it has been detected that the extinction of endangered species of different taxonomic groups would cause functional diversity loss (e.g., Ali et al., 2023; Carmona et al., 2021; Rodríguez‐Caro et al., 2023; Toussaint et al., 2021) and a constraint of the functional space, i.e., the theoretical space whose dimensions are traits or functional strategies in which each species occupies a position based on its characteristics (Rodríguez‐Caro et al., 2023). At smaller scales, the extinction of such species causes a loss of functional diversity leading to more functionally homogeneous communities (e.g., Soares, Palmeirim, et al., 2022; Villéger et al., 2014).…”