The influence of matrix habitat on Aphthona flea beetle immigration to leafy spurge patches

Variation in movement ability by insects among different non-habitat (matri x) types may have important implications for both metapopulation dynamics a nd weed biocontrol practices. We used a mark-recapture experiment to explor e the effects of two different matrix habitats (grass vs shrub) on the abil ity of two species of Aphthona (Chrysomelidae: Coleoptera) flea beetle to i mmigrate to patches of the invasive weed, leafy spurge. Using generalized l inear models, we compared effects of the matrix habitat types, species and sex on observed immigration probabilities. Our analyses demonstrated that o ne species (A. nigriscutis) had a much higher immigration probability when moving through a grass-dominated matrix than a shrub-dominated matrix where as immigration probabilities for the second species (A. lacertosa) were sim ilar in both matrix habitats but significantly lower overall than for A. ni griscutis. Furthermore, A. nigriscutis females were more likely to immigrat e to spurge patches embedded in a grass matrix than in shrub, whereas the o pposite occurred for males. Our results suggest that metapopulation dynamic s may be strongly affected by the type(s) of matrix habitat present on a la ndscape. These effects also suggest that release strategies for weed biocon trol should be tailored according to the structure of the landscape into wh ich releases are planned. in addition, even closely related species can hav e significantly different movement abilities which will also affect release strategies.