Life histories and community structure of Ephemeroptera and Plecoptera in two Alaskan subarctic streams

Abstract

Development of water quality and quantity standards required for improved management of stream fisheries depends on understanding life cycles of the major benthic components. Because temperature is a major factor influencing aquatic insect life histories, subarctic streams provide excellent opportunities to examine organisms existing under extreme environmental conditions. Life histories and community structure of Ephemeroptera and Plecoptera were examined in two Alaskan subarctic streams during 1979 and 1980. Biweekly benthos samples were collected during the ice-free period in a second and a fourth order stream. Seventeen stonefly species and at least seven mayfly species were collected as nymphs or adults. Nymphal abundance and biomass were greater for all taxa in erosional zones (P < 0.05). Coexistance of systematically-related species occurred because of seasonal separation of life histories, or differ­ences in food exploitation patterns.