Environment, community & the individual; characterising the ecology of aquatic invasive alien plants in Ireland
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Date
2018
Authors
Reidy, Darren T.
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Publisher
University College Cork
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Abstract
The Irish freshwater environment is particularly vulnerable to invasion by alien species. Given the importance of invasive alien species as drivers and passengers of ecological change it is pertinent that the mechanisms and processes involved in the invasion of Irish aquatic habitats are better understood. The overarching aim of this research was to characterise the relevant traits, of the environment, biological communities and individuals, responsible for the successful dispersal, establishment and spread of alien macrophytes. To that end, invasive alien macrophyte species (including Elodea canadensis, Elodea nuttallii, Lagarosiphon major and Myriophyllum aquaticum) were studied in situ and ex situ, combining field surveys, comparative experiments and molecular techniques. Hypotheses relating to propagule pressure, habitat disturbance, resource availability, community invasibility, stress tolerance and cryptic invasions were tested. It was found that the occurrence and distribution of invasive alien species in standing waterbodies in Ireland is substantially greater than previously recorded. 54% of surveyed waterbodies were found to be invaded. The intensity of human amenity use was the best predictor of the occurrence of invasive alien species and there was a positive association between nutrient concentrations and the occurrence and abundance of some invasive species. The influence of alien species was additive to the native community, increasing the complexity of native assemblages in terms of richness, biomass, diversity and function of invaded ecosystems. It was found that those native species that were excluded by alien species tended to be morphologically similar. Most invasive species studied had high capacity to tolerate fragmentation and desiccation indicating their capacity to overcome barriers to reproduction, dispersal and colonization. Using a combination of lab and field based experiments, M. aquaticum was shown to utilise phenotypic plasticity in its tolerance of saline conditions, and was capable of colonising and invading brackish waters. A molecular investigation of alien Myriophyllum spp. in Ireland revealed genetic diversity amongst and between populations of the clonal species M. aquaticum. The discovery of multiple cryptic taxa (M. heterophyllum and M. sp. “red 1”) originating in the horticultural trade is of particular concern. Implications for the management of aquatic invasive species in Ireland are discussed.
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Keywords
Macrophytes , Elodea canadensis , Elodea nuttallii , Lagarosiphon major , Myriophyllum aquaticum , Propagule pressure , Stress tolerance , Cryptic invasions , Freshwater ecology , Aquatic invasive species , Plant communities , Abiotic characteristics , Invasion ecology
Citation
Reidy, D. T. 2018. Environment, community & the individual; characterising the ecology of aquatic invasive alien plants in Ireland. PhD Thesis, University College Cork.