Investigating the role of traits in species invasiveness in marine and terrestrial ecosystems

Abstract

Invasive species have been identified as one of the leading causes of global biodiversity loss. Understanding why some introduced non-native species become invasive whilst others do not, is a major focus of invasion ecology. Addressing this key knowledge gap is required to effectively manage current biological invasions and to predict and therefore prevent the introduction of future invaders. Measurable characteristics of an organism, or species traits, provide a common metric that can be used across different taxa and ecosystems to better understand ecological processes underpinning biological invasions. To investigate how traits can be used to understand the processes of invasive species in their novel environment, I focused on two broad taxonomic groups, terrestrial plants and seaweeds (i.e. marine macroalgae). First, I investigated whether different forms of invasiveness, specifically a binary classification of invasive and non-invasive, and continuous dimensions of invasiveness (local abundance, geographic range size, environmental range size, and spread rate), were correlated with different traits. To do this I made use of a published dataset of invasive and non-invasive terrestrial plants from Czechia. Different traits were associated with dimensions of invasiveness than were found using the binary classification alone. However, traits consistently explained the binary classification better than the continuous dimensions, showing that both approaches are valuable to identify traits associated with species invasiveness. Second, I undertook a systematic review that aimed to quantitatively summarise research that has investigated traits of invasive seaweeds. I found that there were a growing number of papers investigating this research area, spanning a range of methodologies and aims, with morphological traits being the most commonly measured trait group. Research gaps included a lack of papers investigating more than one species, and studies of biomechanical traits. Third, I tested the importance of enemy release for the success of two invasive seaweed species in the UK, through herbivory experiments and by comparing defence traits with six functionally similar native seaweed species. I found no evidence to support the enemy release hypothesis as an important mechanism in the invasiveness of two UK seaweeds, and that the traits related to defence against herbivory did not explain patterns in herbivore choice. Finally, I investigated how traits of native species can influence the dispersal and introduction of invasive species, through sequencing seaweed pathogens. I found the first record of the Maullinia pathogen in New Zealand, which was closely related to pathogen populations previously found in Chile. From this I inferred that the pathogen was likely dispersed through buoyant seaweed species, which had rafted for tens of thousands of kilometres. Ultimately, this thesis adopted a multi-faceted approach to better understand how traits can be used to investigate invasive species in their novel environment, in both terrestrial and marine ecosystems.

More information

Identifiers

ORCID for Abigail Lisa Mabey: orcid.org/0000-0003-0156-1881

ORCID for Jane A Catford: orcid.org/0000-0003-0582-5960

Catalogue record

Export record