A sex-specific size-number tradeoff in clonal broods
Polyembryonic parasitoids producing single-sex broods of clonal offspring provide an unusually clear window into the classic tradeoff between the number and size of offspring. We conducted a laboratory study of the encyrtid parasitoid Copidosoma bakeri parasitizing the noctuid Agrotis ipsilon to exa...
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Published in | Oikos Vol. 118; no. 10; pp. 1552 - 1560 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Oxford, UK
Blackwell Publishing Ltd
01.10.2009
Blackwell Publishing Blackwell |
Subjects | |
Online Access | Get full text |
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Summary: | Polyembryonic parasitoids producing single-sex broods of clonal offspring provide an unusually clear window into the classic tradeoff between the number and size of offspring. We conducted a laboratory study of the encyrtid parasitoid Copidosoma bakeri parasitizing the noctuid Agrotis ipsilon to examine the way that size and number of offspring tradeoff in broods of each sex and to determine how the fit between host and parasitoid brood is achieved. We found that brood mass (wasp body mass × brood size) was proportional to host mass, independent of brood sex, indicating a tight fit between brood and host and ensuring a size–number tradeoff. By correcting brood size and body mass of each brood for host mass, we demonstrated the expected inverse relationship between wasp variables. We postulated that the wasp brood might achieve the fit to the host by (1) adjusting brood size based on information available early in host development before and during division of the embryo, (2) manipulating host size late in host development after completion of embryo division, or (3) simply adjusting individual wasp mass to fill the host. We evaluated host responses to parasitism – and correlations between brood size and host growth early and late in development – for broods of each sex. The data are consistent with adjustment of brood size to the amount of host growth early in host development and with manipulation of host mass late in host development. The tight link between host mass and brood mass also suggests a final adjustment by parasitoid growth to achieve complete filling. Within the tight fit, female broods were smaller but contained larger individuals than male broods. The sex-specific balance point of the tradeoff and sex differences in balancing mechanisms and responses to host size suggest different selection pressures on each sex requiring future investigation. |
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Bibliography: | istex:D4BB44BF4692642E094F33645900AA650F4D1EC8 ark:/67375/WNG-9CXDPRJD-6 ArticleID:OIK17571 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0030-1299 1600-0706 |
DOI: | 10.1111/j.1600-0706.2009.17571.x |