The long-term effects of interspecific competition on density dependent emigration

Density dependent emigration (DDE) is thought to be an important mechanism regulating population densities and species coexistence. However, little empirical evidence has been given to demonstrate its long-term impacts on population level dynamics. Moreover, little attention is given to how interspecific competition influences the pattern of DDE. Here, we investigate DDE over generational time under interspecific and intraspecific competitive scenarios using two congeneric species of Tenebrionid beetles: the Red Flour Beetle (RFB), Tribolium castaneum, and the Confused Flour Beetle (CFB), Tribolium confusum. Additional treatments include patch size and patch permeability. Experiments are conducted at 70% RH and 30⁰C. In single species trials, both RFB and CFB demonstrate positive DDE. Smaller patch size and increased patch permeability yields significantly higher proportion of emigrants. In mixed species trials where the two species are engaged in competition, RFB emigration is positively density dependent in relation to its own density, but not in regard to the density of CFB. The emigration of CFB appears to be independent of both its own density and that of RFB. In these mixed species trials, patch permeability remains a significant indicator of proportion emigrated for both species and patch size, interestingly, is no longer significant.