Disentangling the historical routes to community assembly in the global epicentre of biodiversity

Abstract

Understanding the processes through which ecological communities are assembled remains a major challenge, particularly in hotspots of biodiversity such as tropical mountains. Here, we apply continuous-time Markov models to elevational, geographical and phylogenetic data for 166 avian sister pairs to infer the relative frequency of different historical pathways involved in the build-up of species on Neotropical mountains, the Earth's most biodiverse terrestrial region. We show that sister species arising in geographic isolation but now sympatric (i.e. living on the same mountain slope), have assembled through a mix of different routes. Ecological sorting whereby species diverge to different elevations in allopatry occurs with a similar frequency to ecological displacement where divergence in elevation occurs upon secondary contact. However, both these routes are far less common than ecological niche conservatism, whereby species transition to sympatry without diverging in their elevation range. Our results suggest the predominance of this more direct and thus faster route to sympatry may help explain the exceptional species richness of tropical mountains.

An elevational shift facilitated the Mesoamerican diversification of Azure‐hooded Jays (Cyanolyca cucullata) during the Great American Biotic Interchange

“…Still, until more information becomes available, perhaps from data on species' ecologies and interactions, the weight of the evidence in Cyanolyca points toward species sorting, and not interspecific competition, driving elevational zonation and permitting species co‐existence. While interspecific competition has undoubtedly played a large role in elevational zonation in many cases, Cyanolyca presents a counterexample, similar to the Buarremon brush‐finches (Cadena, 2007), where pre‐existing, complementary elevation ranges have allowed for the co‐existence of closely related species after secondary contact (also see Reijenga et al, 2023).…”