Migration in Heterogeneous Environments: Differences in Habitat Selection Between the Wing Forms of the Dimorphic Planthopper, Prokelisia Marginata (Homoptera: Delphacidae)

Abstract

The planthopper, Proklisia marginata, feeds selectively on the intertidal grass, Spartina alterniflora. Populations contain two adult wing forms that vary in proportion from one local area to the next. There are short—winged flightless individual (brachypters) and individuals with fully developed wings (macropters) that fly. Differences in the ability of the two wing forms to select high quality habitats in a heterogeneous environment are measured to elucidate further the advantages of migration (macroptery). Adult planthoppers (both wing forms) occur most abundantly on the parts of individual plants, seed heads in particular, that contain the highest percent crude protein. The percent crude protein in stands of S. alterniflora and the frequency of flowering plants are used as measures of habitat quality and vary considerably over the marsh surface. There is a significant positive relationship between the densities of both wing forms and habitat quality. However, the slope of the regression line for macropters is significantly steeper than for brachypters suggesting that macropters are better able to move from low— to high—quality patches. The relative mobility of wing forms is further documented by the inability of brachypters to colonize small defaunated plots of grass compared to macropters. We suggest variation in habitat quality is unpredictable, that high—quality patches of vegetation may be separated by distances greater than the ambit of brachypters, and that macropters can more effectively track spatial oscillations in habitat quality.