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Title: The effect of environmental variation on species functional traits
Author: Cassidy, Camilla
ISNI:       0000 0004 9349 5726
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2020
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The traits of organisms – their physiological, behavioural or life-history characteristics – determine their ability to both mediate and respond to their environment. Quantification of traits offers a valuable utility through which to represent the functional roles and contributions of species, allowing incorporation of species performance into projections of environmental or ecological change. However, by the predominant use of single or mean trait values, a majority of current trait-based approaches implicitly assume that conspecific individuals are identical, and that species performance will be unaffected by environmental variation. Environmental gradients across spatiotemporal scales and increasing impacts from anthropogenic activity mean that global ecosystems are not uniformly exposed to the same suite of biotic and abiotic factors. The trait expression of component organisms is known to shift in response to these factors, potentially altering species functional contributions, and complicating efforts to predict ecosystem functioning and service provision in the face of widespread change. Under conventional approaches, understanding of ecosystems and recommendations to ecosystem management may be in error. Quantification of intraspecific trait variation may contribute to alleviating these issues, yet this approach has so far received little attention. Here, I explicitly incorporate the magnitude of intraspecific variation into trait-based study, using laboratory-based mesocosm experiments of benthic model systems. My results demonstrate that intraspecific trait variability arises in response to a number of differing biotic and abiotic factors. I show that this variability mechanistically underpins species-level trait responses, forming a fundamental component of biodiversity that determines species interactions and contributions to ecosystem functioning. By developing trait metrics that incorporate this intraspecific variability, I then demonstrate empirically that acknowledging the context-dependency of species’ trait expression alters their assumed functional contributions. While species identity effects prevail across varying contexts, intraspecific trait expression underpins and identifies mechanisms of ecosystem change. Collectively my findings comprise a novel and concise demonstration that quantifying intraspecific traits illuminates the sensitivity of organisms, highlighting the responsiveness of species to ecosystem change. In particular, I draw attention to the extent and importance of dissimilarity between what widely used methodologies would dictate to be identical trait identities. I show that integrating quantification of individual-level trait expression into trait-based ecosystem study adds value, offering mechanistic understanding as to the drivers of community- or ecosystem-level change. In doing so, I highlight the potential benefit these techniques may offer to improve predictive capacities. I conclude that, in order to understand and project the ecosystem consequences of environmental change, it will be necessary to acknowledge the full biodiversity in, and informative capacity offered by, natural systems and the intraspecific diversity they contain.
Supervisor: Godbold, Jasmin Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available