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Ecological complexity of non-native species impacts in desert aquatic systems

Henkanaththegedara, Sujan Maduranga

Titre : Ecological complexity of non-native species impacts in desert aquatic systems

Auteur : Henkanaththegedara, Sujan Maduranga

Université de soutenance : NORTH DAKOTA STATE UNIVERSITY

Grade : Doctor of Philosophy (Ph.D) 2012

Without an adequate understanding of complex interactions between native and nonnative species, management of invasive species can result in unforeseen detrimental impacts. I used both field mesocosm experiments and laboratory predation trials to study reciprocal species interactions between the endangered Mohave tui chub (Siphateles bicolor mohavensis) and invasive western mosquitofish (Gambusia affinis). I also examined the impacts of both fish species on the aquatic invertebrate communities in desert springs. I show a case of intraguild predation (IGP) as a mechanism facilitating co-persistence of endangered tui chub with invasive mosquitofish using field mesocosm experiments. This case of IGP appears to be size structured with adult Mohave tui chub preying on adult (and juvenile) mosquitofish, and adult mosquitofish preying on tui chub eggs and/or larvae. These results collectively suggest size structured IGP between these two fish species as the mechanism for copersistence. In light of these findings, managers may consider habitats currently harboring mosquitofish as possible refuge sites for Mohave tui chub, an option previously un-available. I conducted laboratory predation trials to assess the role of predator gape-limitation in the context of IGP between these two fish species. I explored sex specific differences in gape-size limitation in mosquitofish, because mosquitofish are highly dimorphic. Larval tui chubs had lower survival in the presence of female mosquitofish than in the presence of males. Reciprocally, adult tui chubs preyed upon adult mosquitofish causing a lower survival for male mosquitofish compared to female survival. These results combined with vulnerability modeling show that IGP in this system is size structured based on gape-size limitation.In addition to complex reciprocal interactions, recently established fish populations may impact unique invertebrate communities. Mesocosm experiments with sympatric and allopatric populations of tui chub and mosquitofish showed changes of invertebrate community structures mainly due to population declines and local extirpations of invertebrates, presumably due to fish predation. These results may suggest important conservation implications of invasive fish as well as protected fish transplants into fishless desert springs. Overall my research emphasizes the importance of considering complex ecological interactions between native and non-native species in management of invasive and protected fish species as well as unique invertebrate communities in fishless springs in desert ecosystems.

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Page publiée le 26 octobre 2013, mise à jour le 6 mars 2019