Document Type
Article
Publication Title
Ecosphere
Publication Date
9-2019
Keywords
Aedes, Culex pipiens, density dependence, overcompensation, predator–prey
Abstract
Extrinsic mortality impinging on negative density-dependent populations can result in no change in the number of survivors (compensation) or an increase (overcompensation) by releasing the population from density-dependent effects on survivorship. The relationship between the level of extrinsic mortality (i.e., percentage of mortality) and the level and likelihood of overcompensation is theoretically important, but rarely investigated. We tested the hypothesis that overcompensation occurs below a threshold value of extrinsic mortality that is related to density-dependent mortality rate and that additive extrinsic mortality occurs above this threshold. This hypothesis predicts that survivorship vs. extrinsic mortality will (1) be best described by a two-segmented model with a threshold; (2) have a slope >0 below the threshold; and (3) have a slope = −1 above the threshold. We also tested whether mortality imposed by real predators and random harvest have equivalent effects on adult production and whether magnitude of overcompensation is related to species sensitivity to density dependence. These hypotheses were tested in the container mosquitoes Aedes aegypti, Aedes albopictus, Aedes triseriatus, and Culex pipiens (Diptera: Culicidae). Cohorts of 150 larvae were exposed to random harvest of 0–70% two days after hatch or to predation by 1–3 Mesocyclops longisetus (Crustacea: Copepoda). Overcompensation occurred in A. aegypti in a pattern consistent with predictions. Aedes triseriatus showed strong overcompensation but no evidence of a threshold, whereas A. albopictus and C. pipiens had survival consistent with compensatory mortality but no evidence of a threshold. Compared to random harvest, mortality from predation yielded greater adult production in A. aegypti and A. albopictus, lesser adult production in C. pipiens, and no difference in adult production in A. triseriatus. Our results are largely consistent with our hypothesis about overcompensation, with the caveat that thresholds for additive mortality appear to occur at very high levels of extrinsic mortality. Magnitudes of overcompensation for the three Aedes were inversely related to survival in the 0% mortality treatment, consistent with our hypothesis that overcompensation is related to sensitivity to density dependence. A broad range of extrinsic mortality levels can yield overcompensation, which may have practical implications for attempts to control pest populations.
Funding Source
NIAID grant 1R15AI124005-001 to SAJ and a Phi Sigma Biological Honor Society (Beta Lambda chapter) Robert D. Weigel Fund grant and Mockford-Thompson Fellowship to Z. Neale funded this work.
Recommended Citation
Neale, Zoey R. and Juliano, Steven A., "Finding the sweet spot: What levels of larval mortality lead to compensation or overcompensation in adult production?" (2019). Faculty Publications – Biological Sciences. 141.
https://ir.library.illinoisstate.edu/fpbiosci/141
DOI
10.1002/ecs2.2855
Appendix S1
Comments
First published in Ecosphere volume 10, issue 9 (Sep 2019). https://doi.org/10.1002/ecs2.2855.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.