Colonization of host plants by Tamalia galling aphids during succession following wildfire

Fire is a major mode of disturbance maintaining chaparral ecosystems in California. The heat and smoke characterizing fires act to stimulate germination of manzanita (Arctostaphylos) shrubs, which constitute a major element of the chaparral. As succession proceeds in the wake of fire, young shrubs are colonized first by gall-inducing Tamalia aphids, followed closely by congeneric inquiline (gall-invading) aphids. Following a 1999 wildfire in the Cascade Range foothills, we have tracked the appearance of young plants and their colonization by Tamalia aphids beginning in 2008. We tested the hypothesis of minimum dispersal distance to predict relative rates of colonization by gall-inducers and inquilines. Results suggest inquilines can disperse and colonize new habitats efficiently, in synchronization with their gall-inducing hosts. Our results have implications for patterns of evolutionary diversification in both gall-inducer and inquiline lineages.