Egg load evolution in parasitoids

J. Ellers*, J. G. Sevenster, G. Driessen

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Parasitic wasps lay their eggs in or on other insects. Allocation of resources to reproduction (eggs) and survival (life span) should maximize reproductive success, but stochasticity in the number of hosts encountered precludes an exact match of allocation with reproductive opportunity. We study optimal egg loads using a general model for pro-ovigenic parasitoids (which only mature eggs before adult life) and a dynamic programming model for synovigenic parasitoids (which can mature additional eggs during adult life). We find that stochasticity has a major effect on optimal egg loads and that the patchy distribution of hosts is the major source of stochasticity in reproductive opportunities. In a stochastic world, the further "relative habitat quality" (expected number of oviposition opportunities gained by reducing reproductive investment by one egg) is below unity (as we argue it generally is), the more the optimal egg load exceeds the expected number of hosts. In unusually rich environments, however, stochasticity decreases optimal egg loads. Although synovigenic parasitoids can adjust to the conditions they encounter, they too have to invest for an uncertain future. Because they can replenish their egg supply throughout life, the incidence of egg limitation is even lower than in pro-ovigenic parasitoids.

Original languageEnglish
Pages (from-to)650-665
Number of pages16
JournalThe American Naturalist
Volume156
Issue number6
DOIs
Publication statusPublished - 2000

Keywords

  • Allocation trade-off
  • Egg limitation
  • Habitat stochasticity
  • Optimal fecundity
  • Patch aggregation
  • Reproductive investment

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