Date of Award

Spring 1-1-2016

Document Type

Thesis

Degree Name

Master of Arts (MA)

First Advisor

Pieter T. Johnson

Second Advisor

Deane Bowers

Third Advisor

Kendi Davies

Abstract

Aquatic macroinvertebrates play key roles in structuring aquatic communities and provide a key link with the surrounding terrestrial environment through their metamorphosis from aquatic larvae to terrestrial adults. It is therefore important to understand how their distribution across a landscape shifts through time and in response to environmental change, such as prolonged drought. Concurrently, because relatively little is known about the parasites that use pond macroinvertebrates as hosts, I also explored the relative importance of factors affecting infection prevalence and parasite load within common invertebrate host taxa. For each year over four years, I sampled 36 ponds within the Bay Area of California, USA, to characterize the diversity and composition of aquatic macroinverebrates and quantify the parasites that utilize these organisms as hosts. I specifically aimed to answer the following questions: (1) what are the relative influences of non-native fishes and hydroperiod in structuring communities? (2) How does the magnitude of such filters vary through time? And (3) how do host- and habitat-level factors combine to determine patterns of infection with larval dragonflies and damselflies? My results indicated that while fish play a dominant role in structuring the macroinvertebrate composition and richness, the strength of this effect was attenuated during a prolonged drought such that, by the last year of the study and the height of California superdrought, fish had no detectable effect on the macroinverebrate diversity or species composition. The parasite survey revealed six parasite taxa using macroinvertebrates as hosts with the majority infecting members of the Odonata (dragonflies and damselflies). The hierarchical generalized mixed model results suggested that the majority of variation in both infection prevalence and load was associated with site-level variables, such as water chemistry, and with an interaction between the presence of fish and host suborder. These findings suggest that infection probability for odonates is more closely linked to site-level factors than host-level factors though there are potential interactions between the two levels that must be considered.

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