Discussion
Our results show, on the one hand, how age-dependent changes in carrying capacity affect the overall properties of the island’s trait space and, on the other hand, how those changes are a consequence of species interactions. Those interactions increase in strength as the island niche space becomes filled through time, favouring the presence of a non-random combination of functions. This agrees with the idea that species interactions at the community level drive species diversity in island systems (Wilson 1969). Our work also aligns with recent studies on island biogeography, proposing to move beyond a strictly species richness-centred approach through the use of functional traits to infer the processes shaping island assemblages (Ottaviani et al. 2020; Schrader et al. 2021). We here show how, by assigning functional identities to each species in the island’s assemblage, it is possible to derive the assumptions of island biogeographic theory—which, in essence, describes the macroecological state of an island in a given time—from the description of island’s communities interactions. Through the test of time (Patiño et al. 2017; Whittaker et al. 2017), island biogeography theory proved to be a milestone idea in ecology and evolution, allowing us to understand the impact of ecological dynamics and historical contingencies on the biodiversity of a broad range of systems beyond islands (e.g., Dawson 2016; Ottaviani et al. 2020, Dunn et al. 2022). Given the essentially transferable nature of trait-based approaches (Weiss & Ray 2019), addressing island biogeography models through a mechanistic description of trait states is a key step to generalise these predictions even further.