Intraspecific competition as it relates to organism density and space use among Simuliidae larvae.

Abstract

Intraspecific competition as it relates to organism density and space use among filter feeding Simuliidae larvae was investigated at the University of Michigan Biological Station (Pellston, MI). This study was conducted to determine if organism density is an important factor in determining the degree of intraspecific competition among larvae on varying habitats. Artificial streams were set up containing four densities of organisms (500, 200, 50, or 25). Each stream contained two rock sizes: small and large (relative to each other). The stream density, rock area, and the number of fights (bumping or biting between larvae) per rock were recorded for three trials. The current velocity remained constant at 4.26 cm/s. A Fisher Multiple Comparison ANOVA between density and area was used to interpret the data. There was s definite relationship between the number of fights and organism density. In general, as the number of organisms increased, the number of fights also rose. It was found that there was no significant difference between the 500 and 200 density streams in the number of fights per area of small rock. However, there was a significant difference among the other streams in the #fights/area of small rock. On the other hand, with the large rocks there was a significant differnce among streams, 500 vs. 200, 500 vs. 50, and 500 vs. 25. There was no significant difference among the other streams in the #fights/area of large rock. Thus, there were more fights with the larger density streams as the larvae compete to remain on the prime habitat, the larger rock. From this data, it can be inferred that population density if related to the degree of intraspecific competition among larvae for living space.