tailieunhanh - Reproductive senescence and dynamic oviposition behaviour in insects

The ASRM meeting produced evidence that the current oversight of ART could be improved by the addition of insurance coverage for infertility treatments. Such coverage could promote the most medically appropriate procedures and reduce the incidence of multiple births with their accompanying risks and costs. Insurance coverage for infertility could also strengthen existing oversight and quality controls by requiring adherence to ASRM guidelines or performance of ART procedures only at clinics subject to SART standards. While properly crafted language in a widely adopted medical practice act requiring specialists in ART to follow ASRM guidelines unless otherwise indicated might improve the uniformity of practice nationwide, it is important to recognize. | Evolutionary Ecology 1998 12 871-879 Reproductive senescence and dynamic oviposition behaviour in insects MARC MANGEL1 and GEORGE E. HEIMPEL2 1 Department of Environmental Studies University of California Santa Cruz CA 95064 and 2Department of Entomology University of Wisconsin Madison WI53706 USA Summary We explore the relationship between clutch size behaviour and the likelihood of egg limitation in insects with parasitoid-like life histories. We compare the incidence of egg limitation in insects that produce clutch sizes consistent with maximizing fitness per host . the single host maximum or Lack clutch size with insects exhibiting two types of dynamic behaviour. In the first case insects produce clutch sizes according to a rule that specifies a negative relationship between egg complement and clutch size in the second case clutch size is determined by both egg complement and the host encounter rate using a dynamic state-variable model. The analyses are an extension of models presented by Rosenheim 1996 which predicted a strong positive relationship between the risk of egg limitation and the host encounter rate in the absence of dynamic oviposition behaviour. Our results are consistent with Rosenheim s but they show that dynamic behaviour can greatly reduce the risk of egg limitation and weaken the relationship between the host encounter rate and egg limitation. Keywords dynamic modelling egg limitation insect clutch size oviposition behaviour parasitoids reproductive senescence Introduction When a female insect exhausts her egg supply . becomes egg-limited she experiences reproductive senescence cf. Finch 1990 . An important potential cost associated with this form of senescence is the loss of reproductive opportunity. For insects with parasitoid-like life histories sensu Price 1975 these opportunity costs can be manifested either by hosts that remain unutilized due to egg limitation or by the production of low-quality offspring prior to egg limitation.