Physiological adaptations to climate change in pro-ovigenic parasitoids Damien Denis a,n , Jean-Se ´ bastien Pierre a , Joan van Baaren a , Jacques J.M. van Alphen a,b,c a UMR 6553 ECOBIO, Universite´ de Rennes I, Campus de Beaulieu, Avenue du Ge ´ne´ral Leclerc, 35 042 Rennes cedex, France b Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, PO Box 94248, 1090 GE Amsterdam, The Netherlands c Netherlands Centre for Biodiversity Naturalis, PO Box 9517, 2300 RA Leiden, The Netherlands article info Article history: Received 21 April 2011 Received in revised form 5 June 2012 Accepted 6 June 2012 Available online 20 June 2012 Keywords: Parasitoids Pro-ovigenic Climate change Egg load Stochastic dynamic programming abstract Temperature increase can affect physiological and behavioural constraints. Here, we use a stochastic dynamic modelling approach to predict changes in physiological adaptations and behaviour in response to temperature increase of pro-ovigenic parasitoids (i.e., parasitoids that mature all of their eggs before emergence). Adults of most species of parasitoids, are not capable of de novo lipogenesis. The allocation of lipids accumulated during the larval stage determines adult lifespan and fecundity. In females, lipids can be allocated either to egg production or to adult lipid reserves leading to a trade-off between fecundity and lifespan. Our results show that selection by an increase in ambient temperature, favours a smaller initial egg load and a larger amount of lipids for maintenance. The cost of habitat exploitation increases with temperature because the rate of lipid consumption increases. Hence, lifetime reproductive success decreases. When the optimal activity rate shifts to match the higher ambient temperature, these effects become less pronounced. & 2012 Elsevier Ltd. All rights reserved. 1. Introduction Levitus et al. (2001) estimate that the global mean temperature has risen by 0.6 70.2 1C over the past century. In the near future, this increase in temperature is expected to accelerate. Some models predict that in the next decade global mean temperature will increase from 0.3 to 1.3 1C and temperate regions will probably experience a greater increase in temperature than tropical ones (Knutti et al., 2002; Stott and Kettleborough, 2002). It is difficult to predict how animal populations might adapt to a warmer climate because an increase in temperature could lead to a shift in distribution pattern (Pearson, 2006; Peterson et al., 2002), to changes in phenology (reviewed in Visser and Both, 2005), and in adaptation of morphology, physiology and beha- viour (Root et al., 2003; Walther, 2002; Hance et al., 2007; Gienapp et al., 2008). The evolutionary response of a species to a warmer climate will most likely include all of these, and investigation of each of these possible responses is needed for integrative predictions about the ability of animals to adapt to changes in climate. Several studies have investigated the physiological and beha- vioural responses that individual organisms use to cope with an increase in temperature. Temperature increase may affect metabolic and development rates (Huey and Kingsolver, 1989; Logan et al., 1976) or induce migration behaviour (Pearson, 2006; Peterson et al., 2002). Insect parasitoids are a useful biological model for investi- gating the effects of climate change on fitness, because their physiological and behavioural responses can easily be measured under laboratory conditions, and because there is a direct link between foraging behaviour and fitness. Moreover, adults of most parasitoid species, are incapable of de novo lipogenesis, and the allocation of lipids accumulated during the larval stage determines the budget for longevity and fecundity (Casas et al., 2005; Visser and Ellers, 2008; Visser et al., 2010). In females, lipids can be allocated to either egg production or stored as reserves leading to a trade-off between fecundity and longevity (Ellers and van Alphen, 1997; Pexton and Mayhew, 2002). Pro-ovigenic parasitoids, because they mature all their eggs during pre-adult development, are a suitable model to explore the effect of temperature on this trade off. In response to an increase in average temperature, parasitoids could shift the trade-off between fecundity and longevity and adapt their rate of activity. The observation that ectotherms from temperate and tropical areas differ in thermal tolerance can be taken as evidence that natural selection has shaped activity patterns in relation to ambient temperature (Addo-Bediako et al., 2000; Deutsch et al., 2008). Like other ectotherms, para- sitoids can adjust their activity rate as a function of temperature (Hance et al., 2007). As yet, no theory has been developed to predict how selection by a warmer climate would affect physiol- ogy and behaviour of parasitoids. Predicting such effects is not Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/yjtbi Journal of Theoretical Biology 0022-5193/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jtbi.2012.06.005 n Corresponding author. E-mail address: joan.van-baaren@univ-rennes1.fr (Joan van Baaren). Journal of Theoretical Biology 309 (2012) 67–77