Altitudinal Distribution and Abundance of Trichoptera in a Rocky Mountain Stream
The larvae of 30 + species of Trichoptera in 10 families were collected from rubble riffles in a Colorado flowage, from alpine tundra to the plains. Mean larval density exhibited a general increase downstream, from 338 larvae per m2 in the alpine tundra stream to 3967 larvae per m2 at the plains location. Limnephilidae occurred over the entire attitudinal gradient and was the only family at the upper two sites. Only Limnephilidae and Rhyacophilidae were collected above 3000 meters. Some species were restricted to the headwaters, others to middle or lower reaches, whereas a few species occurred over a wide range of altitude. A sharp faunal break was apparent between the lower foothills and the plains. Seven species of Rhyacophila, which exhibited overlapping distribution patterns in the middle reaches, all occurred sympatrically on riffles at 3109 and 2816 meters elevation. Diversity and abundance patterns of Trichoptera are associated with gradients in physicochemical parameters and biotic factors.
KeywordsMiddle Reach Altitudinal Gradient Larval Density Alpine Tundra Altitudinal Distribution
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