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Dispersal strategies of phytophagous insects at a local scale: adaptive potential of aphids in an agricultural environment.

Lombaert E, Boll R, Lapchin L - BMC Evol. Biol. (2006)

Bottom Line: We further show that the effect of dispersal parameters on aphid fitness depended strongly on plant characteristics.Parameters defining the dispersal strategies of aphids at a local scale are key components of the fitness of these insects and may thus be essential in the adaptation to agricultural environments that are structured in space and time.Moreover, the fact that the effect of dispersal parameters on aphid fitness depends strongly on plant characteristics suggests that traits defining aphid dispersal strategies may be a cornerstone of host-plant specialization.

View Article: PubMed Central - HTML - PubMed

Affiliation: Unité de Lutte Biologique, INRA, 06903 Sophia-Antipolis, France. lombaert@antibes.inra.fr

ABSTRACT

Background: The spread of agriculture greatly modified the selective pressures exerted by plants on phytophagous insects, by providing these insects with a high-level resource, structured in time and space. The life history, behavioural and physiological traits of some insect species may have evolved in response to these changes, allowing them to crowd on crops and to become agricultural pests. Dispersal, which is one of these traits, is a key concept in evolutionary biology but has been over-simplified in most theoretical studies. We evaluated the impact of the local-scale dispersal strategy of phytophagous insects on their fitness, using an individual-based model to simulate population dynamics and dispersal between leaves and plants, by walking and flying, of the aphid Aphis gossypii, a major agricultural pest, in a melon field. We compared the optimal values for dispersal parameters in the model with the corresponding observed values in experimental trials.

Results: We show that the rates of walking and flying disperser production on leaves were the most important traits determining the fitness criteria, whereas dispersal distance and the clustering of flying dispersers on the target plant had no effect. We further show that the effect of dispersal parameters on aphid fitness depended strongly on plant characteristics.

Conclusion: Parameters defining the dispersal strategies of aphids at a local scale are key components of the fitness of these insects and may thus be essential in the adaptation to agricultural environments that are structured in space and time. Moreover, the fact that the effect of dispersal parameters on aphid fitness depends strongly on plant characteristics suggests that traits defining aphid dispersal strategies may be a cornerstone of host-plant specialization.

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Effect of dispersal parameters on fitness criteria. Effect of varying walking (Aw, Bw) and flying (Af, Bf) disperser aphid production parameters on the maximum number of aphids observed in the greenhouse (nmax, solid lines) and the production of propagules (nprop, doted lines). Arrows indicate the experimentally observed values of the parameters. Half error bars represent the standard deviation obtained from the 10 simulations of each point.
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Figure 3: Effect of dispersal parameters on fitness criteria. Effect of varying walking (Aw, Bw) and flying (Af, Bf) disperser aphid production parameters on the maximum number of aphids observed in the greenhouse (nmax, solid lines) and the production of propagules (nprop, doted lines). Arrows indicate the experimentally observed values of the parameters. Half error bars represent the standard deviation obtained from the 10 simulations of each point.

Mentions: Fig. 3 shows the values of the two fitness criteria, nmax and nprop (see methods), when each of the four dispersal parameters were varied individually, the other three parameters in each case being set to the values estimated from Experiment 1. Sets of 10 simulations were run for each of 21 values from 0 to 0.15 for Aw, from -1 to 0.7 for Bw, from 0 to 10-6 for Af and from 1.5 to 4 for Bf. Both optimality criteria were maximal for a range of values of Aw between 0.005 and 0.03 when the observed value was 0.0238. For Bw, both criteria were maximal for a range of values between -0.5 and 0.1 when the observed value was 0.01. nmax increased sharply then gradually decreased for values of Af above 5E-8, and nprop increased continuously with Af when the observed value was 2.16E-9. A maximum of nmax was observed for Bf = 2.4 and a maximum of nprop was obtained with Bf = 3 when the observed value was 1.97. The observed values for the dispersal parameters of walking individuals were thus compatible with the optimal fitness calculated with the simulation model. In contrast, the observed dispersal parameters of flying individuals gave calculated fitness parameters far lower than the theoretical maximum.


Dispersal strategies of phytophagous insects at a local scale: adaptive potential of aphids in an agricultural environment.

Lombaert E, Boll R, Lapchin L - BMC Evol. Biol. (2006)

Effect of dispersal parameters on fitness criteria. Effect of varying walking (Aw, Bw) and flying (Af, Bf) disperser aphid production parameters on the maximum number of aphids observed in the greenhouse (nmax, solid lines) and the production of propagules (nprop, doted lines). Arrows indicate the experimentally observed values of the parameters. Half error bars represent the standard deviation obtained from the 10 simulations of each point.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1622755&req=5

Figure 3: Effect of dispersal parameters on fitness criteria. Effect of varying walking (Aw, Bw) and flying (Af, Bf) disperser aphid production parameters on the maximum number of aphids observed in the greenhouse (nmax, solid lines) and the production of propagules (nprop, doted lines). Arrows indicate the experimentally observed values of the parameters. Half error bars represent the standard deviation obtained from the 10 simulations of each point.
Mentions: Fig. 3 shows the values of the two fitness criteria, nmax and nprop (see methods), when each of the four dispersal parameters were varied individually, the other three parameters in each case being set to the values estimated from Experiment 1. Sets of 10 simulations were run for each of 21 values from 0 to 0.15 for Aw, from -1 to 0.7 for Bw, from 0 to 10-6 for Af and from 1.5 to 4 for Bf. Both optimality criteria were maximal for a range of values of Aw between 0.005 and 0.03 when the observed value was 0.0238. For Bw, both criteria were maximal for a range of values between -0.5 and 0.1 when the observed value was 0.01. nmax increased sharply then gradually decreased for values of Af above 5E-8, and nprop increased continuously with Af when the observed value was 2.16E-9. A maximum of nmax was observed for Bf = 2.4 and a maximum of nprop was obtained with Bf = 3 when the observed value was 1.97. The observed values for the dispersal parameters of walking individuals were thus compatible with the optimal fitness calculated with the simulation model. In contrast, the observed dispersal parameters of flying individuals gave calculated fitness parameters far lower than the theoretical maximum.

Bottom Line: We further show that the effect of dispersal parameters on aphid fitness depended strongly on plant characteristics.Parameters defining the dispersal strategies of aphids at a local scale are key components of the fitness of these insects and may thus be essential in the adaptation to agricultural environments that are structured in space and time.Moreover, the fact that the effect of dispersal parameters on aphid fitness depends strongly on plant characteristics suggests that traits defining aphid dispersal strategies may be a cornerstone of host-plant specialization.

View Article: PubMed Central - HTML - PubMed

Affiliation: Unité de Lutte Biologique, INRA, 06903 Sophia-Antipolis, France. lombaert@antibes.inra.fr

ABSTRACT

Background: The spread of agriculture greatly modified the selective pressures exerted by plants on phytophagous insects, by providing these insects with a high-level resource, structured in time and space. The life history, behavioural and physiological traits of some insect species may have evolved in response to these changes, allowing them to crowd on crops and to become agricultural pests. Dispersal, which is one of these traits, is a key concept in evolutionary biology but has been over-simplified in most theoretical studies. We evaluated the impact of the local-scale dispersal strategy of phytophagous insects on their fitness, using an individual-based model to simulate population dynamics and dispersal between leaves and plants, by walking and flying, of the aphid Aphis gossypii, a major agricultural pest, in a melon field. We compared the optimal values for dispersal parameters in the model with the corresponding observed values in experimental trials.

Results: We show that the rates of walking and flying disperser production on leaves were the most important traits determining the fitness criteria, whereas dispersal distance and the clustering of flying dispersers on the target plant had no effect. We further show that the effect of dispersal parameters on aphid fitness depended strongly on plant characteristics.

Conclusion: Parameters defining the dispersal strategies of aphids at a local scale are key components of the fitness of these insects and may thus be essential in the adaptation to agricultural environments that are structured in space and time. Moreover, the fact that the effect of dispersal parameters on aphid fitness depends strongly on plant characteristics suggests that traits defining aphid dispersal strategies may be a cornerstone of host-plant specialization.

Show MeSH
Related in: MedlinePlus