Limits...
Optimal resource allocation to survival and reproduction in parasitic wasps foraging in fragmented habitats.

Wajnberg E, Coquillard P, Vet LE, Hoffmeister T - PLoS ONE (2012)

Bottom Line: Although the associated ecological consequences have been studied by several authors, the evolutionary effects on interacting species have received little research attention.As observed in real animal species, the model is based on the existence of a negative trade-off between survival and reproduction resulting from competitive allocation of resources to either somatic maintenance or egg production.The evolutionary consequences of these results are discussed.

View Article: PubMed Central - PubMed

Affiliation: INRA, Sophia Antipolis Cedex, France. wajnberg@sophia.inra.fr

ABSTRACT
Expansion and intensification of human land use represents the major cause of habitat fragmentation. Such fragmentation can have dramatic consequences on species richness and trophic interactions within food webs. Although the associated ecological consequences have been studied by several authors, the evolutionary effects on interacting species have received little research attention. Using a genetic algorithm, we quantified how habitat fragmentation and environmental variability affect the optimal reproductive strategies of parasitic wasps foraging for hosts. As observed in real animal species, the model is based on the existence of a negative trade-off between survival and reproduction resulting from competitive allocation of resources to either somatic maintenance or egg production. We also asked to what degree plasticity along this trade-off would be optimal, when plasticity is costly. We found that habitat fragmentation can indeed have strong effects on the reproductive strategies adopted by parasitoids. With increasing habitat fragmentation animals should invest in greater longevity with lower fecundity; yet, especially in unpredictable environments, some level of phenotypic plasticity should be selected for. Other consequences in terms of learning ability of foraging animals were also observed. The evolutionary consequences of these results are discussed.

Show MeSH

Related in: MedlinePlus

Effect of habitat patch quality and the probability for a parasitoid female to emerge on a host-containing habitat patch on the optimized values of the parameter G2.Average (±SE) optimized values of G2 defining the range of phenotypic plasticity (see Figure 1) for parasitoid females foraging for hosts in environments with different habitat patch qualities and having different probabilities to start their life on a habitat patch.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3368906&req=5

pone-0038227-g005: Effect of habitat patch quality and the probability for a parasitoid female to emerge on a host-containing habitat patch on the optimized values of the parameter G2.Average (±SE) optimized values of G2 defining the range of phenotypic plasticity (see Figure 1) for parasitoid females foraging for hosts in environments with different habitat patch qualities and having different probabilities to start their life on a habitat patch.

Mentions: The cost associated to phenotypic plasticity (G2) has an obvious effect (Fig. 4). The higher the cost, the less females should invest in being phenotypically plastic (F4,736 = 18.71, p<0.0001). However, when the cost is not too high, it becomes profitable to maintain some phenotypic plasticity, especially when females cannot be certain they will find hosts in their natal habitat patch (effect of the probability to be born on a host-containing habitat patch: F4,736 = 13.18, p<0.0001). The optimized level of phenotypic plasticity was also influenced by the quality of the habitat patches available in the environment (F6,736 = 18.02, p<0.0001; Fig. 5). That is, in low-quality habitat patches, it appeared that the probability that a female starts her life on a host-containing habitat patch was not important. In this case, females should have an intermediate level of phenotypic plasticity. The most likely reason for this is that, under these conditions, females spend a little time on small patches and a large amount of time travelling between habitat patches. Thus, whether or not they start their life by dispersing would not have a significant importance. With better-quality patches, however, being phenotypically plastic becomes important for females that are uncertain about starting their life on a host-containing habitat patch or not, i.e., for intermediate values of p. Furthermore, the optimal level of phenotypic plasticity significantly increased with the time females spend travelling between patches (F4,736 = 34.48, p<0.0001; Fig. 6). When the time needed to reach each habitat patch is short, females spend most of their time on habitat patches containing hosts and are thus optimally allocating their resources to fecundity rather than to survival (see Fig. 2), without a need to maintain a substantial level of phenotypic plasticity. In contrast, when the time needed to reach each habitat patch increases, females should invest more into longevity (see Fig. 2), but should be able to trade this back for eggs when hosts are encountered. In these cases, phenotypic plasticity should be maintained.


Optimal resource allocation to survival and reproduction in parasitic wasps foraging in fragmented habitats.

Wajnberg E, Coquillard P, Vet LE, Hoffmeister T - PLoS ONE (2012)

Effect of habitat patch quality and the probability for a parasitoid female to emerge on a host-containing habitat patch on the optimized values of the parameter G2.Average (±SE) optimized values of G2 defining the range of phenotypic plasticity (see Figure 1) for parasitoid females foraging for hosts in environments with different habitat patch qualities and having different probabilities to start their life on a habitat patch.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3368906&req=5

pone-0038227-g005: Effect of habitat patch quality and the probability for a parasitoid female to emerge on a host-containing habitat patch on the optimized values of the parameter G2.Average (±SE) optimized values of G2 defining the range of phenotypic plasticity (see Figure 1) for parasitoid females foraging for hosts in environments with different habitat patch qualities and having different probabilities to start their life on a habitat patch.
Mentions: The cost associated to phenotypic plasticity (G2) has an obvious effect (Fig. 4). The higher the cost, the less females should invest in being phenotypically plastic (F4,736 = 18.71, p<0.0001). However, when the cost is not too high, it becomes profitable to maintain some phenotypic plasticity, especially when females cannot be certain they will find hosts in their natal habitat patch (effect of the probability to be born on a host-containing habitat patch: F4,736 = 13.18, p<0.0001). The optimized level of phenotypic plasticity was also influenced by the quality of the habitat patches available in the environment (F6,736 = 18.02, p<0.0001; Fig. 5). That is, in low-quality habitat patches, it appeared that the probability that a female starts her life on a host-containing habitat patch was not important. In this case, females should have an intermediate level of phenotypic plasticity. The most likely reason for this is that, under these conditions, females spend a little time on small patches and a large amount of time travelling between habitat patches. Thus, whether or not they start their life by dispersing would not have a significant importance. With better-quality patches, however, being phenotypically plastic becomes important for females that are uncertain about starting their life on a host-containing habitat patch or not, i.e., for intermediate values of p. Furthermore, the optimal level of phenotypic plasticity significantly increased with the time females spend travelling between patches (F4,736 = 34.48, p<0.0001; Fig. 6). When the time needed to reach each habitat patch is short, females spend most of their time on habitat patches containing hosts and are thus optimally allocating their resources to fecundity rather than to survival (see Fig. 2), without a need to maintain a substantial level of phenotypic plasticity. In contrast, when the time needed to reach each habitat patch increases, females should invest more into longevity (see Fig. 2), but should be able to trade this back for eggs when hosts are encountered. In these cases, phenotypic plasticity should be maintained.

Bottom Line: Although the associated ecological consequences have been studied by several authors, the evolutionary effects on interacting species have received little research attention.As observed in real animal species, the model is based on the existence of a negative trade-off between survival and reproduction resulting from competitive allocation of resources to either somatic maintenance or egg production.The evolutionary consequences of these results are discussed.

View Article: PubMed Central - PubMed

Affiliation: INRA, Sophia Antipolis Cedex, France. wajnberg@sophia.inra.fr

ABSTRACT
Expansion and intensification of human land use represents the major cause of habitat fragmentation. Such fragmentation can have dramatic consequences on species richness and trophic interactions within food webs. Although the associated ecological consequences have been studied by several authors, the evolutionary effects on interacting species have received little research attention. Using a genetic algorithm, we quantified how habitat fragmentation and environmental variability affect the optimal reproductive strategies of parasitic wasps foraging for hosts. As observed in real animal species, the model is based on the existence of a negative trade-off between survival and reproduction resulting from competitive allocation of resources to either somatic maintenance or egg production. We also asked to what degree plasticity along this trade-off would be optimal, when plasticity is costly. We found that habitat fragmentation can indeed have strong effects on the reproductive strategies adopted by parasitoids. With increasing habitat fragmentation animals should invest in greater longevity with lower fecundity; yet, especially in unpredictable environments, some level of phenotypic plasticity should be selected for. Other consequences in terms of learning ability of foraging animals were also observed. The evolutionary consequences of these results are discussed.

Show MeSH
Related in: MedlinePlus