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

Abstract

In the hymenopteran parasitoid Venturia canescens, asexual (obligate thelytoky not induced by Wolbachia bacteria) and sexual (arrhenotokous) wasps coexist in field conditions despite the demographic cost incurred due to the production of males by sexual females. Arrhenotoky predominates in field conditions, whereas populations in indoor conditions (mills, granaries) are exclusively thelytokous. These differences in the relative abundance of the two modes of reproduction between environments suggest that the individuals of each reproductive mode may have developed strategies adapted to the conditions prevailing in each kind of habitat. The two environments contrast in temperature variability and in the spatial heterogeneity of host availability. In this study, we considered the combined effect of temperature and host availability on host patch exploitation by thelytokous and arrhenotokous V. canescens. As expected, arrhenotokous females were more sensitive to temperature changes. If the temperature decreased before foraging, they remained longer and exploited patches more thoroughly. This is consistent with the expected behaviour of parasitoids in response to signs of unfavourable conditions that entail increasing risk of time limitation or a reduced probability of attaining further patches. Both arrhenotokous and thelytokous females increased patch exploitation with host availability. However, unexpectedly, we found no difference in the way the two types of wasp responded to differences in host availability. Differences in the strategies adopted under different environmental conditions may indicate divergence of niche-specific life history traits between the two modes of reproduction. Niche displacement may partly account for the coexistence of these two modes of reproduction at a geographical scale.

Differential energy allocation as an adaptation to different habitats in the parasitic wasp Venturia canescens

“…Therefore, we cannot claim that the differences found are a general feature of the two reproductive modes. However, previous results showing (1) consistent differences between the two modes of reproduction in line with adaptive considerations (Li et al 2003;Amat et al 2006;Thiel et al 2006) and (2) a lack of influence of geographical location Thiel et al 2006), strengthen the findings of this work.…”

Are individuals from thelytokous and arrhenotokous populations equally adept as biocontrol agents? Orientation and host searching behavior of a fruit fly parasitoid

“…Ardeh et al (2005a, b) found no differences between arrhenotokous and thelytokous Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae) with respect to host discrimination. Amat et al (2006) saw no differences in the oviposition behaviors of arrhenotokous and thelytokous Venturia canescens Gravenhorst (Hymenoptera: Ichneumonidae), although arrhenotokous females exhibited longer patch residence times. Subsequently, Amat et al (2009) found similar responses by both populations to parasitized hosts, but thelytokous females adjusted their patch residence time by using cues from conspecifics while arrhenotokous wasps did not.…”

Occurrence of arrhenotoky and thelytoky in a parasitic wasp Venturia canescens (Hymenoptera: Ichneumonidae): Effect of endosymbionts or existence of two distinct reproductive modes?

“…Recent studies on V. canescens appear to demonstrate niche differentiation that could explain the coexistence of the two reproductive modes, i.e. thelytokous individuals seem to be more adapted to anthropogenic and arrhenotokous individuals to natural habitats (Amat et al, 2006(Amat et al, , 2009Thiel et al, 2006;Pelosse et al, 2007Pelosse et al, , 2010Foray et al, 2011). Future studies should investigate the genetic basis of thelytoky in V. canescens since thelytoky in the parasitoid wasp Lysiphlebus fabarum (Hymenoptera: Braconidae) is determined by a single recessive gene (Engelstädter et al, 2011;Sandrock & Vorburger, 2011).…”

“…A key point of contention is in the imbalance between the obvious demographic and genetic costs of sex (Maynard-Smith, 1978) vs the lack of demonstrated short term advantages. Niche differentiation, highlighted by environmental dependent differences in fitness of sexual and asexual forms, seems to be a fruitful avenue of investigation to resolve this issue (Amat et al, 2006(Amat et al, , 2009Tobler & Schlupp, 2010). In order to evaluate this hypothesis, it is necessary to compare closely related sexual and asexual species or individuals of the same species that occur sympatrically.…”

“…In the hymenopteran parasitoid, Venturia canescens Gravenhorst (Hymenoptera: Ichneumonidae), the natural co-occurrence of wasps with two different modes of reproduction, arrhenotoky (called "sexual") and thelytoky ("asexual"), has been interpreted as evidence for two coexisting modes of reproduction (Schneider et al, 2002;Amat et al, 2006;Thiel et al, 2006;Pelosse et al, 2007) rather than the induction of thelytokous parthenogenesis. However, the prevalences of reproductive parasites in V. canescens has to be clarified because Cook & Butcher (1999) and EMMANUEL DESOUHANT that prokaryotes are unlikely to be implicated in the thelytokous parthenogenesis in V. canescens.…”