Effects of environmental parameters on predacious diving beetle (Coleoptera: Dytiscidae) abundance and species richness among three habitat types in southern Mississippi

Predacious Diving Beetles, as both avid dispersers and predators, likely have important ecological roles in aquatic habitats. Little is known about the important environmental factors that affect dytiscid abundance and richness patterns among aquatic habitats. For this study, dytiscids were sampled from 67 sites in Southern Mississippi using dip nets. Sites examined included ponds, ditches, and tire ruts. Ponds were defined as naturally formed, ditches intentionally man-made, and ruts accidental. For each site we measured average canopy cover, aquatic vegetation cover, and depth. Total area also was calculated per habitat. Based on logistic regression analysis of the four habitat parameters, only increasing canopy cover had a significant weak negative effect on beetle presence. MANOVA indicated that habitat types only varied significantly by depth with ruts significantly shallower compared to other habitats. There were no significant differences in the total number of beetle species or individuals among the habitat types, suggesting the measured parameters may have little influence by themselves. Of the 17 species identified, five were common, and two displayed different abundance patterns among habitat categories. Mean abundance of Laccophilus proximus was higher in ruts compared to ponds, whereas mean abundance of Liodessus cantralii was higher in ditches compared to other habitats. Results for Laccophilus proximus may support its hypothesized role as colonizer of new habitats. The study suggests that dytiscid communities do not strongly vary among these habitats although the fact that a few individual species seem to prefer some habitats over others may point to non-random beetle assemblages.