An exploration of the effects of productivity, predators, and nutrient enrichment on metacommunity structure

Abstract

To understand patterns in biodiversity, we first need to understand how it is organized across the landscape. Diversity can be measured in a single patch of habitat as the number of species and number of individuals per species, but patches do not exist in isolation. By organizing the landscape into a collection of patches of habitat, we can define the broader diversity of the metacommunity. By identifying changes to diversity in a single patch (local diversity or alpha diversity) and determining the heterogeneity of diversity among patches (turnover or beta diversity), we can begin to can predict changes in diversity across the landscape (regional diversity or gamma diversity). The aim of this dissertation was to investigate how abiotic and biotic factors influence beta diversity across multiple spatiotemporal scales using a variety of diversity metrics. Using a long-term dataset, I was able to determine that the relationship between primary productivity and species turnover varied across years in part due to annual fluctuations in environmental conditions. To answer questions about how changes to habitat suitability affected community assembly, I conducted experiments in artificial ponds to test the effects of predation and nitrogen enrichment on macroinvertebrates. Fish presence in ponds had a stronger effect on prey diversity than newt or Anax presence, reducing overall richness while increasing abundance of lower-trophic level taxa with some differences across spatial scales. Moderate nitrogen enrichment in ponds increased taxonomic heterogeneity and the heterogeneity of traits present among patches in the metacommunity, but overall, there were signs of functional redundancy across the metacommunity. Together, these results show the breadth of applications of metacommunity ecology for predicting the effects of multiple environmental factors on biodiversity across spatial and temporal scales.