Mahon, M. B. | Search bioRxiv

bioRxiv2021

Functional similarity, not phylogenetic relatedness, predicts the relative strength of competition

Predicting the outcome and strength of species interactions is a central goal of community ecology. Researchers have proposed that outcomes of species interactions (competitive exclusion and coexistence) are a function of both phylogenetic relatedness and functional similarity. Studies relating phylogenetic distance to competition strength have shown conflicting results. Work investigating the role of phylogenetic relatedness and functional similarity in driving competitive outcomes has been limited in terms of the breadth of taxa and ecological contexts examined, which makes the generality of these studies unclear. Consequently, we gathered 1,748 pairwise competition effect sizes from 269 species and 424 unique species pairs with divergence times ranging from 1.14 to 1,275 million years and used meta-regression and model selection approaches to investigate the importance of phylogenetic relatedness and functional similarity to competition across ecological contexts. We revealed that functional similarity, but not phylogenetic relatedness, predicted the relative strength of interspecific competition (defined as the strength of interspecific competition relative to intraspecific competition). Further, we found that the presence of predators, certain habitats, increasing density of competitors, and decreasing spatial grain of experiments were all associated with more intense interspecific competition relative to intraspecific competition. Our results demonstrate that functional similarity, not phylogenetic relatedness, may explain patterns of competition-associated community assembly, highlighting the value of trait-based approaches in clarifying biotic assembly dynamics.

ecology↗

bioRxiv2020

Reservoir host community and vector density predict human tick-borne diseases across the United States

In the United States, tick-borne disease cases have tripled since the 1990s and cost upwards of 10 billion USD annually. Tick density and densities and diversity of non-human mammalian reservoir hosts are hypothesized to drive tick-borne disease dynamics and are targets for interventions. Here, we relate human prevalence of four tick-borne diseases (Lyme disease, monocytic ehrlichiosis, granulocytic anaplasmosis, and babesiosis) to tick and reservoir host community data collected by the U.S. National Ecological Observatory Network (NEON) across the contiguous U.S. We show that human disease prevalence is correlated positively with tick and reservoir host densities and negatively with mammalian diversity for Lyme disease and ehrlichiosis, but positively for anaplasmosis and babesiosis. Our results suggest that the efficacy of tick-borne disease interventions depends on tick and host densities and host diversity. Thus, policymakers and disease managers should consider these ecological contexts before implementing preventative measures. SignificanceTick-borne disease incidence has increased in the United States over the last three decades. Because life-long symptoms can occur if reactive antibiotics are not administered soon after the tick bite, prevention is imperative. Yet, control of tick-borne zoonoses has been largely unsuccessful, at least partly because of a limited understanding of the ecological complexities of these diseases, especially non-Lyme disease tick-borne zoonoses. We use continental-scale data to quantify the relationships among four tick-borne diseases and tick and reservoir host communities, revealing that disease incidence is driven by a combination of tick densities and reservoir host densities and diversity. Thus, the efficacy of tick-borne disease interventions is likely dependent on these ecological contexts.

ecology↗