Ecological and Evolutionary Processes Underpinning Biodiversity Disparities Between Tropical and Temperate Mountains

Abstract

Aim

Although studies have linked mountain radiations to clade diversification rates, it is unclear whether or why these radiations differ between tropical and temperate mountains. Here, we investigated differences in species richness, climatic niche space, lineage accumulation, and diversification rates of a widespread montane shrub between tropical and temperate mountains, and explored the ecological and evolutionary factors that contribute to these disparities.

Location

Global.

Taxon

Gaultheria (Ericaceae), represented by 292 species.

Methods

We built a comprehensive global distribution dataset of the genus and combined it with a dated molecular phylogeny to assess species diversity, climatic niche space, and diversification rates across tropical and temperate mountains. We evaluated the contributions of environmental heterogeneity, climate stability, and other ecological factors to the observed diversity patterns.

Results

The extant diversity of Gaultheria is significantly higher in tropical than in temperate mountains. The variables representing habitat heterogeneity and climate stability were the best predictors of species richness. Niche diversity was significantly higher in tropical mountains, while diversification rate analyses revealed no significant differences between tropical and temperate lineages.

Main Conclusions

Our findings provide empirical evidence that higher species richness in tropical mountains is associated with broader climatic niches, greater environmental heterogeneity, and long-term species persistence rather than elevated diversification rates. These findings provide an improved understanding of the mechanisms shaping the exceptional biodiversity in tropical montane ecosystems and highlight the interplay of ecological and evolutionary processes in shaping regional differences in species richness.