Family planning in a stemborer parasitoid: sex ratio, brood size and size-fitness relationships in Parallorhogas pyralophagus (Hymenoptera: Braconidae) , and implications for biological control
Bernal, J.S.; Gillogly, P.O.; Griset, J.
Bulletin of Entomological Research 91(4): 255-264
2001
ISSN/ISBN: 0007-4853 PMID: 11587621 DOI: 10.1079/ber200199Document Number: 402474
Various aspects were studied of the brood size and sex allocation strategies, and of size-fitness relationships in Parallorhogas pyralophagus (Marsh), a gregarious ectoparasitoid of Eoreuma loftini Dyar. Brood size was significantly correlated with host size; larger hosts were allocated larger broods. Brood sex ratios were fixed precisely at 1 male per 4 females, and eggs were likely to be deposited in that order; differential mortality did not contribute to this precise sex ratio. The sex allocation strategy of P. pyralophagus is likely to conform to strict, i.e. single foundress, local mate competition. Adoption of this strategy is probably influenced by a limited insemination capacity of males; a smaller proportion of females (0.09 vs. 0.21) remained virgin in broods with precise or higher sex ratios (20%), suggesting that rates of outbreeding in the field are low. Other results suggested that fitness in P. pyralophagus was correlated with adult size; longevity and reproductive capacity both increased with adult size in males and females. However, adult size may be more important for females than for males because the differences in reproductive capacity between the largest and smallest individuals was up to 7.3 times greater in females versus < 2 times in males. Reprinted by permission of the publisher.