Factors underlying the investment in alates vs. apterous morphs in the gall-dwelling aphid Tamalia inquilinus

Tamalia is a genus of gall-dwelling aphids specializing on Arctostaphylos host plants. Tamalia inquilinus is a recently described species that appears unable to form its own galls, and instead invades and co-occupies the galls of Tamalia coweni in a parasitic fashion. Tamalia coweni has a life history that is linked to the temporary viability of its galls, which typically support the parthenogenetic production of a single generation of daughters. As such, their life history comprises a rigid alternation between generations of exclusively wingless gall-inducers, and their daughters, exclusively winged morphs that disperse to produce live young on new plant tissue. In contrast, T. inquilinus appears to have a more plastic life history. Whereas investment in alate, dispersing morphs is the fixed outcome of gall induction by T. coweni foundresses, investment decisions are likely influenced by a differing set of cues in T. inquilinus, as is suggested by observed patterns of investment in both morphs throughout T. inquilinus generations. These cues are currently unknown, and they are of particular interest because of the notable deviation of T. inquilinus from its closely related host aphid, and because such a pattern has not been described in detail in a galling aphid species. The current project aims to identify the conditions that lead T. inquilinus to invest in alates instead of apterae by assessing a number of factors reported to be of influence in other aphid species, including population density, host plant and gall quality, and the presence of predators.