DOI: 10.5061/dryad.ps42h
title: Data from: The link between host density and egg production in a parasitoid insect: comparison between agricultural and natural habitats

description: 1. Theory predicts that organisms should invest in overcoming a factor
 that may limit their reproductive success in direct proportion to their
 probability of being limited by it. The occurrence of egg limitation
 (where female insects deplete their eggs while oviposition opportunities
 are still available) is predicted to impose selection for increased
 fecundity at the expense of other fitness components. 2. We tested the
 hypothesis that the fecundity of a proovigenic parasitoid (where females
 emerge with their full egg load) should be positively correlated with the
 mean expectation for oviposition opportunities in the environment. More
 specifically, we tested whether females from agricultural systems, where
 hosts are often relatively abundant, emerge with more eggs than those from
 natural habitats. 3. We studied the proovigenic parasitoid wasp Anagrus
 daanei, which parasitizes eggs of leafhoppers of the genus Erythroneura.
 Erythroneura spp. leafhoppers feed on Vitis spp. (grapes) and are major
 pests of commercial vineyards as well as common herbivores of wild Vitis
 californica, which grows in riparian habitats. We sampled leafhoppers and
 parasitoids from eight vineyards and eight riparian habitats in central
 California. 4. We found that leafhopper density was higher at vineyards
 than in riparian habitats, whereas leafhopper egg size and parasitoid body
 size did not differ among these habitat types. Parasitoids from vineyards
 had higher egg loads than parasitoids from wild grapes, and fecundity was
 positively related to host density across field sites. Parasitoid egg
 volume was larger in natural sites; however, this variation was not
 significantly correlated with host density across field sites. Within a
 single population of parasitoids collected from a vineyard, parasitoid egg
 load was negatively correlated with longevity, suggesting a trade-off
 between reproduction and lifespan. 5. The results may be explained by a
 rapid evolution of reproductive traits in response to oviposition
 opportunities; or alternatively, by the occurrence of maternal effects on
 the fecundity of daughters based on the foraging experience of their
 mothers. 6. The ability of parasitoid fecundity to track mean host
 availability may strengthen the ability of parasitoids to suppress the
 population densities of their hosts, and hence may represent an important
 ecological or eco-evolutionary feedback.
description: Egg
 loadData on tibia length and
 egg loads of newly emerged female Anagrus daanei collected as pupa from
 vineyards and riparian habitats.Egg
 volumeData on tibia length,
 egg load and egg volume of females Anagrus daanei collected from vineyards
 and riparian habitats.Host Egg
 sizeData on egg volumes of
 Erythroneura elegantula leafhopper eggs collected from vineyards and
 riparian habitats.Leafhopper egg
 volume.xlsLeafhoppersData on the number of leafhopper eggs found on grape leaves from vineyards and riparian habitats.LongevityData on egg loads and longevity of females A. daanei collected as pupa from a vineyard.