摘要
What shapes the relative investment in reproduction versus survival of organisms is among the key questions in life history.Proovigenic insects mature all their eggs prior to emergence and are short lived,providing a unique opportunity to quantify their lifetime investments in the different functions.We investigated the initial eggloads and longevity of 2 proovigenic parasitoid wasps:Anagrus erythroneurae and Anagrus daanei,(Hymenoptera:Mymaridae)that develop within leafhopper eggs in both agricultural vineyards and natural riparian habitats in Northern California.We collected Vitis spp.leaves containing developing parasitoids from 3 natural sites(Knight Landing,American River and Putah Creek)and 3 agricultural vineyards(Solano Farm,Davis Campus and Village Homes).We recorded eggloads at parasitoid emergence and female parasitoid longevity with or without honey-feeding.Theory predicts that parasitoids from vineyards(where hosts are abundant)would have higher initial eggloads and lower longevity compared with parasitoids from riparian habitats(where hosts are scarce).Although host density and parasitoid eggloads were,indeed,higher in vineyards than in riparian habitats,parasitoid longevity did not follow the predicted pattern.Longevity without feeding differed among field sites,but it was not affected by habitat type(natural vs agricultural),whereas longevity with feeding was not significantly affected by any of the examined factors.Moreover,longevity was positively,rather than negatively,correlated with eggloads at the individual level,even after correcting for parasitoid body size.The combined results suggest a more complex allocation mechanism than initially predicted,and the possibility of variation in host quality that is independent of size.
