Diet breadth modulates preference - performance relationships in a phytophagous insect community.

In most phytophagous insects, larvae are less mobile than adults and their fitness depends on the plant chosen by their mother. To maximize fitness, adult preference and larval performance should thus be correlated. This correlation is not always apparent and seems to increase with the level of specialisation, i.e. specialists have a stronger preference for high quality host plant species compared to generalists. The aim of this study was to test whether the relationship between female preference and larval performance was stronger for specialists than for generalists within a community of fruit flies (Diptera: Tephritidae). A total of six fruit fly species was used, including four generalists, and two specialists co-existing in La Reunion island (France). We estimated oviposition preference through the number of eggs laid and larval performance through the larval survival on 29 different host plants species belonging to 15 families in the laboratory and evaluated the relationship between these two traits. Preference-performance relationship differed according to the degree of specialisation with a strong positive correlation for specialists and no relationship for generalists. These results substantiate the theory that choosing high quality hosts is more important for specialists that are adapted to survive on fewer host plants than for generalists.