Quintero, I. | Search bioRxiv

bioRxiv2019

Functional community assembly and turnover along elevation and latitude

The drivers of community coexistence are known to vary with environment, but their consistency across latitudes and scales, and resulting conservation implications, remain little understood. Here, we combine functional and phylogenetic evidence along elevations to document strong biotic constraints on coexistence in avian communities in both benign (tropical low elevations) and severely harsh (temperate/polar highlands) environments. Assemblages in both are marked by high assemblage functional uniqueness, whereas in tropical highlands and temperate/polar low elevations there is strong functionally redundancy and pronounced environmental constraints. Only in harsh environments is phylogeny an effective surrogate for functional assemblage structure, reflecting nuanced shifts in the position, shape, and composition of measured multivariate trait space along gradients. Independent of scale and latitude, high elevation assemblages emerge as exceptionally susceptible to functional change.

ecology↗

bioRxiv2019

Interdependent Phenotypic and Biogeographic Evolution Driven by Biotic Interactions

Biotic interactions are hypothesized to be one of the main processes shaping trait and biogeographic evolution during lineage diversification. Theoretical and empirical evidence suggests that species with similar ecological requirements either spatially exclude each other, by preventing the colonization of competitors or by driving coexisting populations to extinction, or show niche divergence when in sympatry. However, the extent and generality of the effect of interspecific competition in trait and biogeographic evolution has been limited by a dearth of appropriate process-generating models to directly test the effect of biotic interactions. Here, we formulate a phylogenetic parametric model that allows interdependence between trait and biogeographic evolution, thus enabling a direct test of central hypotheses on how biotic interactions shape these evolutionary processes. We adopt a Bayesian data augmentation approach to estimate the joint posterior distribution of trait histories, range histories, and co-evolutionary process parameters under this analytically intractable model. Through simulations, we show that our model is capable of distinguishing alternative scenarios of biotic interactions. We apply our model to the radiation of Darwins finches--a classic example of adaptive divergence--and find support for in situ trait divergence in beak size, convergence in traits such as beak shape and tarsus length, and strong competitive exclusion throughout their evolutionary history. Our modeling framework opens new possibilities for testing more complex hypotheses about the processes underlying lineage diversification. More generally, it provides a robust probabilistic methodology to model correlated evolution of continuous and discrete characters.

evolutionary biology↗