Survival in Dalbulus leafhopper vectors improves after exposure to maize stunting pathogens

Using D. maidis and pathogen isolates collected at three field sites along an altitudinal gradient in Mexico, we compared survival in leafhoppers expo sed to healthy maize to those exposed to maize infected with one of four is olates of maize stunting pathogens: two isolates of the corn stunt spiropla sma (CSS, Spiroplasma kunkelii) and two of the maize busby stunt phytoplasm a (MBSP). Survival improved after exposure to either plant pathogen under b oth the cooler and warmer environmental conditions D. maidis is likely to e ncounter during the dry season. Survival varied among leafhoppers from the different field sites, suggesting that gene flow between these populations is limited. The leafhoppers responded differently to the four isolates (i.e ., we noted significant population by exposure interactions), but we found no difference between MBSP and CSS exposure. Finally, we found evidence of local adaptation in one leafhopper population to sympatric. as compared to allopatric, plant pathogens. We have shown with this and our earlier study that aspects of the interaction phenotype in the association between D. mai dis and the plant pathogens are mutualistic and that this association has c onsiderable potential as a model for studies of local adaptation.