Trait-based community and invasion ecology of terrestrial arthropods

Thesis

The search for general rules that predict the form, function and fate of biodiversity is an enduring goal in Ecology. Traits which impact the interactions and fitness of organisms have emerged as useful common currency with which to formulate general and predictive rules about ecological processes. A trait-based framework of community assembly will help to elucidate how ubiquitous processes such as interspecific competition shape and maintain biodiversity, and to predict the impacts of environmental change such as invasions by non-native species. Advances in both areas are needed to explain and address recent widespread changes in the diversity of terrestrial arthropods, organisms representing a massive and functionally significant portion of life on Earth.

In this thesis I first review the burgeoning field of terrestrial arthropod trait-based ecology (Chapter 2). Studying ant assemblages in subtropical Asia, I then use trait-based approaches to investigate the mechanistic causes and functional consequences of assembly processes such as interspecific competition, within the context of invasions by non-native species. I find that invasion leads to a functional homogenization across the landscape which, notably, is unmet by comparable changes in taxonomic diversity (Chapter 3). To investigate underlying processes, I test whether differences in ant species’ morphological traits predict their fine-scale spatial associations in ways consistent with theories on interspecific competition (Chapter 4). At the assemblage level, I then show that two opposing mechanisms of competitive exclusion act varyingly on separate morphological, physiological and behavioural traits, causing the invasion to drive contrasting patterns in functional structure (Chapter 5). Addressing a key limitation of trait-based research, I also demonstrate empirically that decisions to exclude intraspecific trait variability from functional diversity assessments can distort the patterns observed, even overturning the conclusions drawn (Chapter 6).

My work strengthens the foundations for a predictive trait-based ecology of animals in general. It makes specific empirical and methodological contributions to the use of traits for understanding community assembly and the competitive mechanisms determining the impacts of invasions on functional diversity. Building on the work described in this thesis, studies investigating how individual and multidimensional traits determine niche and competitive differences between species will further steer Ecology towards general rules for a predictive understanding of biodiversity and associated ecosystem functions.

Authors: Wong, MKL

• DOI: 10.5287/ora-eraabpa0a
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford