| Description |
Understanding patterns and processes underlying the structure and assembly of ecological communities is a major goal of ecology. Community assembly involves a balance between dispersal events and interactions with biotic and abiotic elements that make up the local environment. Determining which processes dominate and under what circumstances remains unclear for parasite communities. Parasite communities of deer mice are examined to determine whether host traits, parasite interactions, and/or parasite dispersal is important in structuring within host parasite community structure. The results suggest that within host parasite communities accumulate in heavier, older hosts. Parasite dispersal plays a role in structuring parasite communities in deer mice. Helminths and ticks accumulated in older hosts, while fleas and lice did not. Helminths and lice were predicted to accumulate in older hosts because they are associated with their hosts for longer periods of time than ticks and fleas. In studies of parasite communities, it is important to document most, if not all, parasites of interest on or in a host. Using histopathology, I show that deer mice are not infected by parasites in other tissues that are not typically examined during standard parasitological surveys. I also survey rodents in the Great Basin for diseases that are caused by both infectious and non-infectious sources. Two pathogens were found in deer mice: the fungus Emmonsia crescens and the nematode Capillaria hepatica. The most common disease was extramedullary hematopoiesis (11%). I also investigated how habitat change influences species turnover. A major change in the environments of the Intermountain West is the expansion of pinyon-juniper woodlands (P-J). Rodent communities in the Great Basin are assessed to document species turnover following P-J conversion. I found that there was a diversity deficit (immigration credit) following P-J conversion because immigration of new species into P-J converted areas is slower than local species extinction. Diversity may increase if the immigrating species become more abundant. Parasites are also subject to environmental change, but little empirical data exist about how parasites will respond. Resampling historical sites following environmental change suggests that helminth diversity increased throughout the Great Basin region. This change was driven by a decrease in the prevalence and abundance of the pinworm Syphacia peromysci, making the relative abundances of helminth species more even. Complex life cycle parasites appear to be more stable to environmental change than those with direct life cycles because, in this system, complex life cycle parasites have lower host specificity. |
