Host‐associated pre‐mating reproductive isolation between host races of Acrocercops transecta: mating site preferences and effect of host presence on mating

Abstract

1. A correlation between habitat and mating site preference is crucial for reproductive isolation between populations with different ecological requirements in the absence of any other barriers to gene flow. In phytophagous insects, host‐plant preference of ovipositing females has been postulated to directly influence the extent of assortative mating. 2. Although this pleiotropic effect of host preference is commonly postulated in both theoretical and empirical studies in phytophagous insects, few studies have assessed the mating site preferences of both sexes. In herbivorous insects, it is crucial whether males have the same host preference as ovipositing females. 3. This study examines whether males and females have preferences for mating sites and assesses the effects of host presence on mating activity in a leaf‐mining moth, Acrocercops transecta Meyrick (Gracillariidae). This species consists of two host races, which are associated with Juglans ailanthifolia Carr. (Juglandaceae) and Lyonia ovalifolia (Wall.) Drude (Ericaceae). The two host races clearly differ in host preferences of ovipositing females. 4. In an experiment of mating site selection, Lyonia‐associated host race females significantly preferred Lyonia, while males of the Lyonia‐associated host race and both sexes of the Juglans‐associated host race did not show a preference for either plant. The mating activity of the Lyonia‐associated host race was not reduced in the absence of host plants. In the Juglans‐associated host race, however, the proportion of successful matings was significantly reduced when the host was absent. 5. These laboratory experiments provide empirical evidence that the different host associations in A. transecta do not directly lead to host‐induced assortative mating between the two host races as a pleiotropic effect. However, the present results suggest that the combined effects of the mating‐site preference of Lyonia‐associated females and the mating propensity of Juglans‐associated females could contribute to reproductive isolation between the two host races.