Development of a positive preference-performance relationship in an oligophagous beetle: adaptive learning?

The relationship between oviposition preference and larval performance is a central topic in insect-plant biology. In this study we investigate whether the oligophagous flea beetle, Altica fragariae Nakane (Coleoptera: Chrysomelidae: Alticinae) exhibits a positive preference-performance relationship, and whether oviposition preference develops over time. We tested the beetles using four sympatric plant species: Duchesnea indica (the normal host plant), Agrimonia pilosa (a secondary host plant), and Potentilla chinensis and Sanguisorba officinalis (host plants of two other Altica species). In no-choice experiments, both oviposition rate and offspring fitness measures (eclosion rate, development time and body mass) are highest on D. indica. Oviposition rate is much lower on P. chinensis than on A. pilosa, whereas the offspring fitness measures do not differ significantly between these two host plants. Offspring fitness measures are lowest for S. officinalis, and adult females refuse to oviposit on this acceptable non-host in a no-choice situation. Repeated two-choice experiments showed that the proportion of oviposition on one of the novel host plants decreased significantly over time when the alternative host plant was D. indica. Interestingly, in repeated two-choice experiments using A. pilosa and P. chinensis, females mainly fed on A. pilosa but distributed their eggs equally over the two host plants, in accordance with the lack of difference in offspring fitness on those hosts. Together, these results show that A. fragariae females develop a positive preference-performance relationship over time. We suggest that A. fragariae achieves this through adaptive learning of oviposition preference: not only does she learn to discriminate the host plants when there is a fitness difference for her offspring, but also does she fail to discriminate when there is no such fitness difference.