This study attempts to understand some aspects of ecological invasions from the perspective of consumer-resource interactions. Two successful Ponto-Caspian invaders of Irish lacustrine habitats, Hemimysis anomala and Chelicorophium curvispinum, are considered here. I establish that the invasive H. anomala has a higher per capita functional response towards cladoceran prey than does a native analogue, Mysis salemaai, whether consumption occurs alone, in conspecific groups, or in conspecific groups in the presence of a higher fish predator. In addition, the presence of this higher predator reduces the consumption of cladocerans by the natives, but not by the invaders. In situ experiments designed to track the vertical migrations of both mysids further reveal that the functional response of the invader is both higher and. more variable over diurnal periods than that of the native. Thus, the impacts of invaders - or natives - on prey can depend on per capita effects, how these vary spatiotemporally and modulation by con specifics and predators. Where invaders are potential resources for native species, as is the case with C. curvispinum, I demonstrate how two defensive characteristics - the propensity to construct protective tubes and to associate with complex habitat architecture - can systematically dampen interactions with a range of vertebrate and invertebrate predators. I highlight how associating with habitat architecture collapses predator capture rates across body mass distributions and, using artificial manipulations of habitat architecture, I demonstrate how increases in the availability of predator-free space can reduce the magnitude and alter the shape of predatory functional responses. These findings allude to the importance of defensive characteristics in mediating the persistence of C. curvispinum. Altogether, this work demonstrates: (i) the utility of functional responses as impact assessment tools; (ii) the importance of quantifying both top-down and bottom-up contributions to interactions; and (iii) the need to consider the context in which interactions occur.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:680885 |
| Date | January 2015 |
| Creators | Barrios-O'Neill, Daniel |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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