Population dynamics and role of two species of Lepidostoma (Trichoptera: Lepidostomatidae) in an Oregon coniferous forest stream

Year: 
1980
Publications Type: 
Journal Article
Publication Number: 
1835
Citation: 

Grafius, E.; Anderson, N. H. 1980. Population dynamics and role of two species of Lepidostoma (Trichoptera: Lepidostomatidae) in an Oregon coniferous forest stream. Ecology. 61(4): 808-816.

Abstract: 

The aim of this study was to gather quantitative field and laboratory data on the roleof Lepidostoma cascadense (Milne) and Lepidostoma unicolor (Banks) in the processing of coniferneedles in a stream ecosystem.
Samples were collected monthly in a riffle-pool section of Mack Creek, Lane County, Oregon,USA. For L. cascadense, maximum larval density was 812/m2 and instantaneous growth rate was1.5%/d. The larvae grew slowly throughout the winter and pupation occurred in May and June. Incontrast, L. unicolor increased very little in size during the winter and grew very rapidly during Juneand early July, reaching a maximum larval density of 320/m2 and with an instantaneous growth rate(March through July) of 2.7%/d. Production of L. cascadense was estimated as 0.31 g• m-2. yr' andthat of L. unicolor was 0.23 g• m-2. yr-I. In addition to temporal separation in periods of maximumgrowth, the two species occurred in different microhabitats. L. cascadense larvae were found withinthe sediments and debris while L. unicolor occurred on the surface of the debris.
Laboratory studies were conducted with L. unicolor larvae. Consumption and fecal productionrates (measured gravimetrically) increased with higher temperature, greater food density, or longerconditioning time of the food, and decreased with increased size of the larvae.
Production and biomass of L. cascadense and L. unicolor in Mack Creek are minor in relationto other insects in the system. However, because of high consumption rates and low assimilationefficiency, the processing of large particulate organic matter by these two species contributed signif-icantly to the food available to collectors in the study area.
Key words: aquatic; growth; Lepidostoma; life histories; Oregon; population dynamics; respi-ration; shredders.