Shared preferences along stress gradients: how a growth-tolerance trade-off drives unimodal diversity and trait lumping

Environmental gradients are pervasive across ecosystems and play a fundamental role in structuring species distributions and community dynamics. While ecological theory mainly focused on species with distinct preferences for specific niches along the gradient, many natural communities follow an alternative pattern of shared preferences. In such systems, all species prefer the same optimal conditions but differ in their tolerance to harsher environments, according to a growth-tolerance trade-off. Here, we develop a trait-based metacommunity model, based on integrodifference equations, to investigate the development of community structure along a one- dimensional stress gradient with shared preferences. We demonstrate how species interactions, driven by competition, dispersal, and a growth-tolerance trade-off lead to the emergence of patterns such as unimodal diversity distributions and trait lumping. Our model provides a conceptual framework for exploring the processes that shape metacommunities across spatial gradients characterized by shared preferences, offering new insights into this underrepresented class of ecological systems.