Understanding coexistence in natural communities is a central goal in ecology, from distinct phenotypes within species to assemblages of interacting species. Niche partitioning and variation in resource use are mechanisms that can promote coexistence by reducing niche overlap and creating asymmetries in resource use. Such asymmetries can lead to the emergence of communities composed of a mix of generalist and specialist strategies, particularly when resources vary in both their energy content and handling effort. Different strategies for resource acquisition are hypothesized to be constrained by trade-offs, which can favor one strategy at the cost of the other. We used a classic consumer-resource model to study diverse communities of consumers subject to trade-offs in resource use.
For a wide range of trade-off strengths, we show ample coexistence between species with final community richness highly influenced by trade-off structure. In particular, structures favoring generalists typically lead to richer communities. Surprisingly, however, we also prove the existence of a "doomsday species" -- a perfect competitor that drives all other species to extinction when introduced in a diverse community. Communities with strong trade-offs favoring specialists are typically less diverse but protected from this doomsday scenario. Our results shed light on how trade-offs acting on the specialist-generalist continuum structure ecological communities with effects on diversity and robustness.