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Host plant quality, spatial heterogeneity, and the stability of mite predator-prey dynamics.

Daugherty MP - Exp. Appl. Acarol. (2010)

Bottom Line: However, the highest level of plant quality did not produce the least stable dynamics, which is inconsistent with the "paradox of enrichment".Heterogeneity in plant productivity had modest effects on stability, with the only significant difference being less variable T. urticae densities in the heterogeneous compared to the corresponding homogeneous treatment.These results are generally congruent with metapopulation theory and other models for spatially segregated populations, which predict that stability should be governed largely by relative movement rates of predators and prey--rather than patch quality.

View Article: PubMed Central - PubMed

Affiliation: Department of Integrative Biology, University of California, Berkeley, CA 94720, USA. matt.daugherty@ucr.edu

ABSTRACT
Population dynamics models suggest that both the over-all level of resource productivity and spatial variability in productivity can play important roles in community dynamics. Higher productivity environments are predicted to destabilize consumer-resource dynamics. Conversely, greater heterogeneity in resource productivity is expected to contribute to stability. Yet the importance of these two factors for the dynamics of arthropod communities has been largely overlooked. I manipulated nutrient availability for strawberry plants in a multi-patch experiment, and measured effects of overall plant quality and heterogeneity in plant quality on the stability of interactions between the phytophagous mite Tetranychus urticae and its predator Phytoseiulus persimilis. Plant size, leaf N content and T. urticae population growth increased monotonically with increasing soil nitrogen availability. This gradient in plant quality affected two correlates of mite population stability, population variability over time (i.e., coefficient of variation) and population persistence (i.e., proportion of plant patches colonized). However, the highest level of plant quality did not produce the least stable dynamics, which is inconsistent with the "paradox of enrichment". Heterogeneity in plant productivity had modest effects on stability, with the only significant difference being less variable T. urticae densities in the heterogeneous compared to the corresponding homogeneous treatment. These results are generally congruent with metapopulation theory and other models for spatially segregated populations, which predict that stability should be governed largely by relative movement rates of predators and prey--rather than patch quality.

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Tetranychus urticae (a) and Phytoseiulus persimilis (b) density (total number of all stages/cm of leaf length per plant) within a cage among fertilizer levels over time
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Fig2: Tetranychus urticae (a) and Phytoseiulus persimilis (b) density (total number of all stages/cm of leaf length per plant) within a cage among fertilizer levels over time

Mentions: Although individual plants in each of the treatments showed dynamics that may represent predator–prey cycles, after averaging among plants and between replicates the treatments all show a strong monotonic decline (Fig. 2). Both predator mite and especially spider mite densities started higher at higher fertilizer levels but declined quickly—to very low densities by the last census. At the end of the study, across all treatments, 41% of plant patches showed local apparent extinction of T. urticae and 48% had no P. persimilis. Densities were consistently low in the Low treatment. For both species, the densities in the Heterogeneous treatment were qualitatively more similar to the Medium treatment than the other two fertilizer levels. The high and low fertilized plants in the Heterogeneous treatment most closely followed the trajectories of the High and Low fertilized treatments, respectively—especially for T. urticae dynamics (Fig. 2a).Fig. 2


Host plant quality, spatial heterogeneity, and the stability of mite predator-prey dynamics.

Daugherty MP - Exp. Appl. Acarol. (2010)

Tetranychus urticae (a) and Phytoseiulus persimilis (b) density (total number of all stages/cm of leaf length per plant) within a cage among fertilizer levels over time
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3040825&req=5

Fig2: Tetranychus urticae (a) and Phytoseiulus persimilis (b) density (total number of all stages/cm of leaf length per plant) within a cage among fertilizer levels over time
Mentions: Although individual plants in each of the treatments showed dynamics that may represent predator–prey cycles, after averaging among plants and between replicates the treatments all show a strong monotonic decline (Fig. 2). Both predator mite and especially spider mite densities started higher at higher fertilizer levels but declined quickly—to very low densities by the last census. At the end of the study, across all treatments, 41% of plant patches showed local apparent extinction of T. urticae and 48% had no P. persimilis. Densities were consistently low in the Low treatment. For both species, the densities in the Heterogeneous treatment were qualitatively more similar to the Medium treatment than the other two fertilizer levels. The high and low fertilized plants in the Heterogeneous treatment most closely followed the trajectories of the High and Low fertilized treatments, respectively—especially for T. urticae dynamics (Fig. 2a).Fig. 2

Bottom Line: However, the highest level of plant quality did not produce the least stable dynamics, which is inconsistent with the "paradox of enrichment".Heterogeneity in plant productivity had modest effects on stability, with the only significant difference being less variable T. urticae densities in the heterogeneous compared to the corresponding homogeneous treatment.These results are generally congruent with metapopulation theory and other models for spatially segregated populations, which predict that stability should be governed largely by relative movement rates of predators and prey--rather than patch quality.

View Article: PubMed Central - PubMed

Affiliation: Department of Integrative Biology, University of California, Berkeley, CA 94720, USA. matt.daugherty@ucr.edu

ABSTRACT
Population dynamics models suggest that both the over-all level of resource productivity and spatial variability in productivity can play important roles in community dynamics. Higher productivity environments are predicted to destabilize consumer-resource dynamics. Conversely, greater heterogeneity in resource productivity is expected to contribute to stability. Yet the importance of these two factors for the dynamics of arthropod communities has been largely overlooked. I manipulated nutrient availability for strawberry plants in a multi-patch experiment, and measured effects of overall plant quality and heterogeneity in plant quality on the stability of interactions between the phytophagous mite Tetranychus urticae and its predator Phytoseiulus persimilis. Plant size, leaf N content and T. urticae population growth increased monotonically with increasing soil nitrogen availability. This gradient in plant quality affected two correlates of mite population stability, population variability over time (i.e., coefficient of variation) and population persistence (i.e., proportion of plant patches colonized). However, the highest level of plant quality did not produce the least stable dynamics, which is inconsistent with the "paradox of enrichment". Heterogeneity in plant productivity had modest effects on stability, with the only significant difference being less variable T. urticae densities in the heterogeneous compared to the corresponding homogeneous treatment. These results are generally congruent with metapopulation theory and other models for spatially segregated populations, which predict that stability should be governed largely by relative movement rates of predators and prey--rather than patch quality.

Show MeSH