The influence of temperature and host availability on the host exploitation strategies of sexual and asexual parasitic wasps of the same species.

AMAT, I.; CASTELO, M.K.; DESOUHANT, E.; BERNSTEIN, C.

OECOLOGIA

SPRINGER BERLIN

Lugar: HEIDELBERG; Año: 2006 vol. 148 p. 153 - 161

0029-8549

1. In the hymenopteran parasitoid Venturia canescens, both asexual (obligate thelytoky not induced by Wolbachia bacteria) and sexual (arrhenotokous) wasps coexist in field conditions and this in spite of the demographical cost incurred by sexual females by producing males. 2. Whilst arrhenotoky predominates in field conditions, populations are exclusively thelytokous in indoor conditions (mills and granaries). 3. The differences in relative abundance of the two modes of reproduction between environments suggest that individuals of each reproductive mode might have developed strategies adapted to the conditions prevailing in each kind of habitat. 4. The two environments contrast in temperature variability and in the spatial heterogeneity of host distribution. This study considers the combined effect of temperature and host availability on host patch exploitation by thelytokous and arrhenotokous V. canescens. 5. As predicted, arrhenotokous females were more sensitive to a change in temperature. When undergoing a decrease in temperature before foraging, they stayed longer and exploited patches more thoroughly. This conforms to the expected behaviour of parasitoids in response to a cue of unfavourable conditions in the near future, and of an increasing risk of time limitation. 6. Unexpectedly, arrhenotokous and thelytokous females did not show any discrepancy in the way they respond to differences in host availability. 7. Differences in the strategies adopted under different environmental conditions could indicate divergence of niche-specific life history traits between both modes of reproduction. Niche displacement may contribute to the explanation of their coexistence at a geographical scale. Key words: coexistence of modes of reproduction, habitat specialisation, patch leaving decision, proportional hazards model, Venturia canescens.