The effects of an invasive species on the structure of native ecosystems

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Gallagher, Mary C.
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University College Cork
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The Australasian barnacle species Austrominius (=Elminius) modestus has been present in Europe for over seventy years, however little is known about how A. modestus interacts with native species, or how its presence may alter ecosystem function. It has been suggested that A. modestus may be an “ecological sleeper”, with the potential to increase in abundance with predicted climate change. This study examined multiple factors that may play a role in determining the invasion success of A. modestus in Ireland and also at sites in Scotland and Portugal, which represent the northern and southern limits of this species in Europe. Long-term monitoring of the colonisation of space by A. modestus and native barnacle species in Ireland revealed a general pattern of coexistence, despite dominance of the non-native species at the majority of study sites. Although A. modestus was found experience enemy release in comparison to native barnacle species, this did not promote reproductive success or abundance. A. modestus was recorded to be widespread but not dominant at its northern and southern limits. Different factors may be controlling the abundance of A. modestus at these locations, with competition playing an important role in the north and desiccation stress at the cypris stage controlling populations in the south. A. modestus was the dominant barnacle species within Lough Hyne marine reserve and on artificial structures surveyed in south-west Ireland. Despite this dominance, native barnacle species continue to persist both in the marine reserve and on artificial structures of varying ages. The continuous production of broods is a key factor in the success of A. modestus as an invasive species. However, the continued availability of free space on the shore, annual variation in recruitment and tolerance of wave-exposed conditions all contribute to the current persistence of native barnacle species in the presence of A. modestus.
Invasive species , Barnacle , Ecosystem structure , Marine ecology , Competition , Enemy release , Range limits , Recruitment
Gallagher, M. C. 2017. The effects of an invasive species on the structure of native ecosystems. PhD Thesis, University College Cork.
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