Effects of temporal variation in temperature and density dependence on insect population dynamics
Abstract Understanding the effects of environmental variation on insect populations is important in light of predictions about increasing climatic variability. This paper uses the univoltine western corn rootworm (WCR, Diabrotica virgifera virgifera LeConte) as a case study and employs deterministic...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Wiley
2016-05-01
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| Series: | Ecosphere |
| Subjects: | |
| Online Access: | https://doi.org/10.1002/ecs2.1287 |
| _version_ | 1818233515720835072 |
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| author | C. V. Haridas Lance J. Meinke Bruce E. Hibbard Blair D. Siegfried Brigitte Tenhumberg |
| author_facet | C. V. Haridas Lance J. Meinke Bruce E. Hibbard Blair D. Siegfried Brigitte Tenhumberg |
| author_sort | C. V. Haridas |
| collection | DOAJ |
| description | Abstract Understanding the effects of environmental variation on insect populations is important in light of predictions about increasing climatic variability. This paper uses the univoltine western corn rootworm (WCR, Diabrotica virgifera virgifera LeConte) as a case study and employs deterministic and stochastic modeling to evaluate how insect population dynamics is shaped by density‐dependent survival and annual variation in temperature, which are key in regulating insect populations. Field data showed that larval survival varied significantly between years but was constant for a range of densities. Survival dropped only beyond a threshold density, a feature resembling generalized Ricker functions used in modeling density‐dependent survival due to scramble competition for resources. We used soil temperature data for 20 yr to model annual variation in developmental time and survival. The deterministic model, where the developmental time was same across years, showed that though survival was high and did not change for a range of densities (i.e., density‐independent survival), predicted densities were large enough that strong density dependence could occur in the field (i.e., predicted densities fall in the region where survival drops sharply) and that populations could exhibit stable equilibrium, cycles, etc. Interestingly, populations with lower density‐independent survival were less likely to produce stable equilibrium compared to populations with higher density‐independent survival. We found that population densities were at stable equilibrium when both mean developmental time and fertility were relatively low or when developmental time and fertility were relatively high. This in turn implies that, in warmer regions, where mean developmental time will be lower, stability is more likely for insect populations with low fertility; species in warmer regions will experience cyclical and unstable dynamics when fertility is high. While increase in the mean developmental time reduces overall survival, increasing variation in developmental time could increase mean survival, a consequence of the Jensen's inequality, since survival was a concave decreasing function of developmental time. Hence, both mean and variability in temperature affect the dynamics of insect populations. Finally, we found that stochastic variation in soil temperature produced large variation in predicted population densities that could potentially enhance or diminish the effect of density dependence. |
| first_indexed | 2024-12-12T11:23:25Z |
| format | Article |
| id | doaj.art-9f3d6e714aea403daedeaed2cccb5706 |
| institution | Directory Open Access Journal |
| issn | 2150-8925 |
| language | English |
| last_indexed | 2024-12-12T11:23:25Z |
| publishDate | 2016-05-01 |
| publisher | Wiley |
| record_format | Article |
| series | Ecosphere |
| spelling | doaj.art-9f3d6e714aea403daedeaed2cccb57062022-12-22T00:25:59ZengWileyEcosphere2150-89252016-05-0175n/an/a10.1002/ecs2.1287Effects of temporal variation in temperature and density dependence on insect population dynamicsC. V. Haridas0Lance J. Meinke1Bruce E. Hibbard2Blair D. Siegfried3Brigitte Tenhumberg4School of Biological Sciences University of Nebraska‐Lincoln 412 Manter Hall Lincoln Nebraska 68588 USADepartment of Entomology University of Nebraska‐Lincoln Lincoln Nebraska 68583 USAPlant Genetics Research Unit University of Missouri Columbia Missouri 65211 USADepartment of Entomology University of Nebraska‐Lincoln Lincoln Nebraska 68583 USASchool of Biological Sciences University of Nebraska‐Lincoln 412 Manter Hall Lincoln Nebraska 68588 USAAbstract Understanding the effects of environmental variation on insect populations is important in light of predictions about increasing climatic variability. This paper uses the univoltine western corn rootworm (WCR, Diabrotica virgifera virgifera LeConte) as a case study and employs deterministic and stochastic modeling to evaluate how insect population dynamics is shaped by density‐dependent survival and annual variation in temperature, which are key in regulating insect populations. Field data showed that larval survival varied significantly between years but was constant for a range of densities. Survival dropped only beyond a threshold density, a feature resembling generalized Ricker functions used in modeling density‐dependent survival due to scramble competition for resources. We used soil temperature data for 20 yr to model annual variation in developmental time and survival. The deterministic model, where the developmental time was same across years, showed that though survival was high and did not change for a range of densities (i.e., density‐independent survival), predicted densities were large enough that strong density dependence could occur in the field (i.e., predicted densities fall in the region where survival drops sharply) and that populations could exhibit stable equilibrium, cycles, etc. Interestingly, populations with lower density‐independent survival were less likely to produce stable equilibrium compared to populations with higher density‐independent survival. We found that population densities were at stable equilibrium when both mean developmental time and fertility were relatively low or when developmental time and fertility were relatively high. This in turn implies that, in warmer regions, where mean developmental time will be lower, stability is more likely for insect populations with low fertility; species in warmer regions will experience cyclical and unstable dynamics when fertility is high. While increase in the mean developmental time reduces overall survival, increasing variation in developmental time could increase mean survival, a consequence of the Jensen's inequality, since survival was a concave decreasing function of developmental time. Hence, both mean and variability in temperature affect the dynamics of insect populations. Finally, we found that stochastic variation in soil temperature produced large variation in predicted population densities that could potentially enhance or diminish the effect of density dependence.https://doi.org/10.1002/ecs2.1287climate changedegree‐daysdensity dependenceDiabrotica virgifera virgifera LeConteenvironmental variationgeneralized Ricker function |
| spellingShingle | C. V. Haridas Lance J. Meinke Bruce E. Hibbard Blair D. Siegfried Brigitte Tenhumberg Effects of temporal variation in temperature and density dependence on insect population dynamics Ecosphere climate change degree‐days density dependence Diabrotica virgifera virgifera LeConte environmental variation generalized Ricker function |
| title | Effects of temporal variation in temperature and density dependence on insect population dynamics |
| title_full | Effects of temporal variation in temperature and density dependence on insect population dynamics |
| title_fullStr | Effects of temporal variation in temperature and density dependence on insect population dynamics |
| title_full_unstemmed | Effects of temporal variation in temperature and density dependence on insect population dynamics |
| title_short | Effects of temporal variation in temperature and density dependence on insect population dynamics |
| title_sort | effects of temporal variation in temperature and density dependence on insect population dynamics |
| topic | climate change degree‐days density dependence Diabrotica virgifera virgifera LeConte environmental variation generalized Ricker function |
| url | https://doi.org/10.1002/ecs2.1287 |
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