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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.

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Trade-off between lifespan and egg load describing the main parameters used in the simulation model.The initial reproductive strategy is defined by G1 and each animal has a certain phenotypic plasticity defined by the range G2, but pays a linearly proportional cost for it, both in survival time and egg load. A third parameter G3 (not shown) defines a learning ability used by the animal to move along such a phenotypic plasticity. Optimal values of the parameters G1, G2 and G3 in different habitats are estimated by means of a genetic algorithm (see text).
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pone-0038227-g001: Trade-off between lifespan and egg load describing the main parameters used in the simulation model.The initial reproductive strategy is defined by G1 and each animal has a certain phenotypic plasticity defined by the range G2, but pays a linearly proportional cost for it, both in survival time and egg load. A third parameter G3 (not shown) defines a learning ability used by the animal to move along such a phenotypic plasticity. Optimal values of the parameters G1, G2 and G3 in different habitats are estimated by means of a genetic algorithm (see text).

Mentions: Animals in the model are assumed to follow a linear trade-off between lifespan and egg load as has been experimentally observed by [31] and [49], and used in theoretical studies by several authors (e.g., [22], [28], [50]). Hence, the model assumes that animals have a limited amount of resources that are allocated either to somatic maintenance and survival or to the production of eggs. The range of such a trade-off was arbitrarily defined to be between 0 and 1000 time steps for longevity, and between 0 and 1000 eggs for egg load. Using different values would lead to a change in scale without qualitatively affecting the results obtained. The reproductive strategy used by each animal along the trade-off was described by a parameter G1 (see Fig. 1), which we expressed in terms of longevity, defining the end point of each simulated generation, the animal running out of either time or eggs to lay.


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)

Trade-off between lifespan and egg load describing the main parameters used in the simulation model.The initial reproductive strategy is defined by G1 and each animal has a certain phenotypic plasticity defined by the range G2, but pays a linearly proportional cost for it, both in survival time and egg load. A third parameter G3 (not shown) defines a learning ability used by the animal to move along such a phenotypic plasticity. Optimal values of the parameters G1, G2 and G3 in different habitats are estimated by means of a genetic algorithm (see text).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0038227-g001: Trade-off between lifespan and egg load describing the main parameters used in the simulation model.The initial reproductive strategy is defined by G1 and each animal has a certain phenotypic plasticity defined by the range G2, but pays a linearly proportional cost for it, both in survival time and egg load. A third parameter G3 (not shown) defines a learning ability used by the animal to move along such a phenotypic plasticity. Optimal values of the parameters G1, G2 and G3 in different habitats are estimated by means of a genetic algorithm (see text).
Mentions: Animals in the model are assumed to follow a linear trade-off between lifespan and egg load as has been experimentally observed by [31] and [49], and used in theoretical studies by several authors (e.g., [22], [28], [50]). Hence, the model assumes that animals have a limited amount of resources that are allocated either to somatic maintenance and survival or to the production of eggs. The range of such a trade-off was arbitrarily defined to be between 0 and 1000 time steps for longevity, and between 0 and 1000 eggs for egg load. Using different values would lead to a change in scale without qualitatively affecting the results obtained. The reproductive strategy used by each animal along the trade-off was described by a parameter G1 (see Fig. 1), which we expressed in terms of longevity, defining the end point of each simulated generation, the animal running out of either time or eggs to lay.

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