Abstract

Using subterranean fauna in the Canary Islands as a simplified natural laboratory, we explored how the interplay of eco-evolutionary processes shape taxonomic and functional diversity patterns in oceanic archipelagos through geological times. First, we demonstrated an overall convergence in the trait spaces of subterranean communities across islands, yet with variability according to each island's ontogenetic state---young, mature, or senescent. Next, we showed that the reduced species contribution to the island's traits space in mature islands is a consequence of an optimisation of the use of the available niche space driven by species interactions. Finally, we link those lines of evidence showing that species interactions select a non-random combination of traits in mature islands. Collectively, our results provided a mechanistic description of the drivers of diversity in oceanic islands by suggesting causal relationships between species functional properties and island diversity metrics accounting for their geological age.