Effect of microenvironment on development of a gall midge.

This study assessed the influence of microenvironment on the establishment and relative reproductive success of the gall-forming midge Rhopalomyia californica Felt on its host plant Baccharis pilularis De Candolle in Marin County, CA. Mesh cages were used to alter the microenvironment, which also allowed us to assess the validity of using these types of experimental manipulations in this system. Temperature, light intensity, wind speed, and stem growth were compared in caged and uncaged B. pilularis plots in two sites during three seasons. Cage presence significantly altered the microenvironment of R. californica but did not affect development. R. californica establishment was greater when growing on host plants with increased stem growth. Season had the largest impact on gall establishment and reproductive success, with the highest establishment and success rates in late winter to early spring, which correlated with the growing period of B. pilularis. These results suggest that the seasonality of R. californica reproductive success is linked to the phenology of its host plant. When the growing conditions for the plant are less than ideal, R. californica performance is stimulated by increased stem growth. Cage presence was not a significant driver of population dynamics because it did not change the environment in an ecologically meaningful way. We therefore assert that the use of cages for experimental manipulations in this study system does not alter R. californica performance.

Non-local concepts and models in biology.

In this paper, we consider local and non-local spatially explicit mathematical models for biological phenomena. We show that, when rate differences between fast and slow local dynamics are great enough, non-local models are adequate simplifications of local models. Non-local models thus avoid describing fast processes in mechanistic detail, instead describing the effects of fast processes on slower ones. As a consequence, non-local models are helpful to biologists because they describe biological systems on scales that are convenient to observation, data collection, and insight. We illustrate these arguments by comparing local and non-local models for the aggregation of hypothetical organisms, and we support theoretical ideas with concrete examples from cell biology and animal behavior.