Ecological succession in the gall aphid, Tamalia coweni (Cockerell, 1905), and its associate, Tamalia inquilinus Miller, 2000 (Hemiptera: Aphididae: Tamaliinae), colonizing Arctostaphylos viscida Parry and Arctostaphylos manzanita Parry (Ericaceae)

Fire is a major ecological process maintaining chaparral ecosystems in California. Following a 1999 wildfire at our study site in the Cascade Range foothills, we have tracked the appearance of young manzanita, Arctostaphylos Adanson (Ericaceae), plants and their colonization by Tamalia Baker, 1920 (Aphididae) aphids beginning in 2003; hence, we have collected data on rates of colonization by the gall-inducers, Tamalia coweni (Cockerell, 1905), and their inquilines, Tamalia inquilinus Miller, 2000. Our methods included mapping the spatial distribution of > 500 host plants in a 1-ha study population using a high-precision Trimble® global positioning system (GPS) instrument and a Geographic Information System (GIS) to process data. We surveyed juvenile shrubs and a random sample of mature plants to estimate the frequency and timing of plants colonized by T. coweni. Additionally, we sampled galls over the growing season to estimate the frequency of inquilines occupying galls. Beginning in 2008, less than 4% of the 135 juvenile plants were colonized by T. coweni as evidenced by the presence of new galls. The proportion of plants colonized has increased continuously; over 85% had been colonized by 2023. Assuming T. coweni colonizes young plants (sinks) from existing populations on mature plants (sources), our results may conform to a minimum dispersal distance hypothesis, although this remains to be tested explicitly. Our data further suggest T. inquilinus can disperse and colonize new habitats efficiently, in synchronization with T. coweni. Our results have implications for patterns of evolutionary diversification in both gall-inducer and inquiline lineages.