Date of Award

Spring 2011

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)


Biological Sciences

Committee Chair

Donald Yee

Committee Chair Department

Biological Sciences

Committee Member 2

Jacob Schaefer

Committee Member 2 Department

Biological Sciences

Committee Member 3

Carl Qualls

Committee Member 3 Department

Biological Sciences


Predaceous diving beetles (Coleoptera: Dytiscidae) are a model group of organisms for testing coexistence and exclusion mechanisms because numerous species of the family interact in isolated, aquatic habitats, and are ubiquitous throughout landscapes. Two morphologically similar species, laccophilus fasciatus rufus and Laccophilus proximus, co-occur in numerous habitats in South Mississippi, but are hypothesized to have strong interspecific interactions. I investigated several possible mechanisms that may promote such coexistence, including segregation in habitat domain, differences in behavior, and differences in dispersal that may allow co-occurrence between these two species of beetle. Habitat domain and behaviors such as activity and prey consumption were quantified in the lab using instantaneous scan censuses and prey competition trails; dispersal was quantified in the field using artifical ponds. Behavioral assays showed no significant difference in habitat domain or behaviors between species, regardless of intra- or interspecific densities. Mass change due to prey consumption was also not affected by intra- or interspecific densities. In the field, L. proximus exhibited a higher dispersal rate compared to L. f rufus, but was not affected by either intra- or interspecific densities. Segregation of habitat domain and behavioral differences are likely not adequate mechanisms explaining within habitat co-occurrence in these two similar species. However, variation in dispersal may allow temporary co-occurrence of these species among habitats. Other mechanisms that may better explain within habitat co-occurrence are discussed. Understanding and identifying these mechanisms of coexistence may assist in the general understanding of multi-predator interactions beyond the family Dytiscidae. lll

Included in

Entomology Commons