Ecological divergence exhibits consistently positive associations with reproductive isolation across disparate taxa

TLDR

Ecological divergence is hypothesized to promote reproductive isolation, yet its general role across taxa has not been systematically tested. The study aims to determine whether ecological divergence consistently predicts reproductive isolation across diverse taxa. We quantified ecological divergence in over 500 species pairs from eight plant, invertebrate, and vertebrate groups and statistically assessed its association with reproductive isolation. The analysis revealed a highly consistent, significant positive association between ecological divergence and reproductive isolation across taxa, across different aspects of ecological divergence and components of reproductive isolation, supporting the hypothesis that ecological adaptation plays a fundamental, taxonomically general role in speciation.

Abstract

To what degree is the divergent adaptation responsible for life’s phenotypic variety also responsible for generating the millions of species that manifest this variation? Theory predicts that ecological divergence among populations should promote reproductive isolation, and recent empirical studies provide support for this hypothesis in a limited number of specific taxa. However, the essential question of whether ecology plays a truly general role in speciation has yet to be systematically evaluated. Here we address this integral issue using an approach that adds an ecological dimension to comparative studies investigating the relationship between reproductive isolation and divergence time. Specifically, we quantify ecological divergence for >500 species pairs from eight plant, invertebrate, and vertebrate taxa and statistically isolate its association with reproductive isolation. This approach demonstrates a highly consistent and significant positive association between ecological divergence and reproductive isolation across taxa. This relationship was also observed across different aspects of ecological divergence and components of reproductive isolation. These findings are highly consistent with the hypothesis that ecological adaptation plays a fundamental and taxonomically general role in promoting reproductive isolation and speciation.