Mito-nuclear selection induces a trade-off between species ecological dominance and evolutionary lifespan

Abstract

Micro-evolutionary processes acting in populations and communities ultimately produce macro-evolutionary patterns. However, current models of species life histories -- including processes of speciation, persistence, hybridization, and eventual extinction -- rarely connect these two time scales. This leaves us with a limited theoretical understanding of the subtleties of diversification, such as the relationship between species abundance in an ecological community and species longevity over evolutionary time, or the impact of selection on patterns of speciation and extinction when structuring an ecological community. Here we present a model for evolution in spatially extended populations with a focus on selection for mito-nuclear compatibility. We find that mito-nuclear selection acting at the individual level decreases genetic variability among species in a radiation, reducing the total number of species and skewing species abundances distributions towards mono-dominance. Also, intraspecific diversity increases as species become more abundant, leading to frequent evolutionary branching that reduces species lifetimes. The equilibrium of such communities is characterized by high rates of speciation, extinction, and hybridization, i.e., high turnover rate. These theoretical results are in concordance with empirical patterns of diversity across latitudinal gradients. Model predictions in the absence of mito-nuclear selection resemble the tropics, with high biodiversity, old species, and low speciation and extinction rates. Whereas model predictions under strong selection, which we expect in the harsh environments of temperate zones, produce fewer species and elevated recent speciation rates.