Competition and brood reduction: testing alternative models of clutch-size evolution in parasitoids

TY - JOUR

T1 - Competition and brood reduction: testing alternative models of clutch-size evolution in parasitoids

AU - Pexton, J.J.

AU - Boer, J.P.

AU - Heimpel, G.E.

AU - Vet, L.E.M.

AU - Whitfield, J.

AU - Ode, P.J.

N1 - Reporting year: 2009 Metis note: 4456;CTE; MTI ; TE; file:///L:/Endnotedatabases/NIOOPUB/pdfs/PDFS2009\Pexton_ea_4456.pdf

PY - 2009

Y1 - 2009

N2 - Competition between siblings occurs in many taxa including parasitoid wasps. Larvae of solitary species eliminate competitors by engaging in aggressive behavior, thus restricting brood size to a single individual. In gregarious species, more than one offspring can develop per host. There are 2 models by which gregariousness can arise in a population of solitary individuals: 1) through a reduction in larval mobility (with the retention of aggressive behavior) or 2) through a reduction in fighting behavior or ability. When more larvae are present than can be supported by available host resources, these 2 models make opposing predictions regarding the process of brood size reduction: Mortality occurring early in larval development under the reduced mobility hypothesis versus mortality occurring throughout larval development under the reduced aggression hypothesis. Here, we measure changes in brood size over the course of larval development of the gregarious parasitoid, Cotesia flavipes. Superparasitized hosts contained approximately twice as many C. flavipes eggs as hosts parasitized by a single parasitoid female. Brood sizes in superparasitized hosts declined gradually as C. flavipes individuals developed, whereas brood sizes remained constant during larval development in singly parasitized hosts. An absence of wounded or destroyed larvae suggested no aggressive behavior. Collectively, these results support the reduced aggression hypothesis.

AB - Competition between siblings occurs in many taxa including parasitoid wasps. Larvae of solitary species eliminate competitors by engaging in aggressive behavior, thus restricting brood size to a single individual. In gregarious species, more than one offspring can develop per host. There are 2 models by which gregariousness can arise in a population of solitary individuals: 1) through a reduction in larval mobility (with the retention of aggressive behavior) or 2) through a reduction in fighting behavior or ability. When more larvae are present than can be supported by available host resources, these 2 models make opposing predictions regarding the process of brood size reduction: Mortality occurring early in larval development under the reduced mobility hypothesis versus mortality occurring throughout larval development under the reduced aggression hypothesis. Here, we measure changes in brood size over the course of larval development of the gregarious parasitoid, Cotesia flavipes. Superparasitized hosts contained approximately twice as many C. flavipes eggs as hosts parasitized by a single parasitoid female. Brood sizes in superparasitized hosts declined gradually as C. flavipes individuals developed, whereas brood sizes remained constant during larval development in singly parasitized hosts. An absence of wounded or destroyed larvae suggested no aggressive behavior. Collectively, these results support the reduced aggression hypothesis.

U2 - 10.1093/beheco/arn147

DO - 10.1093/beheco/arn147

M3 - Article

SN - 1045-2249

VL - 20

SP - 403

EP - 409

JO - Behavioral Ecology

JF - Behavioral Ecology

IS - 2

ER -