Diversity and Distribution of California Dragonflies and Other Aquatic Taxa Over the Past Century

eScholarship, University of California 2014-01-01

Climate and land-use change have altered and continue to affect the diversity, composition, and distribution of freshwater organisms throughout the world. This is particularly true in arid and semi-arid regions, where aquatic organisms may experience more pronounced reductions in available habitat with declines in precipitation, increases in water demand, and habitat degradation through human land-use. However, documentation of changes in taxonomic assemblages over long-time periods has been rare because of the difficulty in obtaining historical occurrence data. This dissertation used data from previously published literature, a resurvey study, museum specimens, and enthusiast sightings to document changes in the occurrence rates and distribution of freshwater organisms throughout California over the past century.Summary information regarding freshwater taxa known to occur in California did not previously exist in a central publication. I therefore conducted a review of several primary groups of stream organisms found in the Mediterranean region of California and statewide. For this work, I gathered data from a variety of literature sources and museum specimens to summarize species composition and endemism in the region, and to identify data gaps and conservation priorities for the examined groups. The remainder of this dissertation focuses largely on changes in Odonata species diversity, composition, and occurrence rates over time in California. This charismatic group was ideal for study of change over time because of their relatively low diversity, well-known taxonomy, and the existence of sufficient historical and current specimen records and more recent enthusiast sightings of odonates.I conducted a resurvey of sites originally sampled for Odonata by Clarence H. Kennedy 1914-1915. This work involved surveys of odonates at 81 sites throughout central California and northwestern Nevada, 45 of which were directly comparable to Kennedy's original sites. I found that

Ecology; Environmental science; Bioinformatics; California; Historical Ecology; Museum Specimens; Odonata; Resurvey; publication

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