Ecological relationships among western Ephemerellidae : growth, life cycles, food habits, and habitat relationships

Graduation date: 1983The purpose of this study was to describe the life cycles,\ud feeding ecology, and habitat use of western species in the mayfly\ud family Ephemerellidae. Data were used to compare the ecological\ud relationships and strategies among species and to examine patterns\ud of adaptive radiation within the family. Data were further used to\ud develop hypotheses describing the general importance of food,\ud temperature, habitat, and season in affecting the development and\ud organization of benthic invertebrate communities in stream\ud ecosystems.\ud Growth rate and length of growth period were examined in nine\ud species. Growth rates of most species were related to temperature,\ud but little evidence was found that implicated food as an important\ud factor affecting individual growth in the field. Growth period and\ud final size were most clearly related to specialization of different\ud species for habitats that differ in duration of stability.\ud Both food specialists and generalists were found among 20\ud species examined for gut contents. Proportion of detritus, diatoms,\ud animal matter, and moss ingested varied among species. Within a\ud species, diet varied with both locality and habitat, but these\ud differences were not sufficient to mask differences in diet among\ud species.\ud Among 14 species, taxa varied in their distribution along a\ud stream continuum (2nd to 7th order) and in their preference for\ud gravel, cobble, boulder, or moss substrates. Most species were\ud habitat specialists and occurred on only one or two substrate types\ud and at only a few stations.\ud When four niche dimensions were considered, overlap between\ud species was found to be least for station, followed by substrate\ud type, season, and food. Complementarity in niche overlaps between\ud niche axes was found for species in the genus Drunella but not among\ud species in the family as a whole.\ud From this study I inferred that stream insects show similar\ud patterns of resource use as do animals in other ecosystems, although\ud evidence for a discrete guild substructure was not strong. I\ud conclude by stressing the need for further research that examines\ud how the multiple and interacting factors in stream ecosystems have\ud shaped both the ecology of single species and the structure of\ud entire communities