Delayed density dependence

In population ecology delayed density dependence describes a situation where population growth is controlled by negative feedback operating with a time lag.[1]

Population cycles

Delayed density dependence has been used by ecologists to explain population cycles.[2] Ecologists have been unable to successfully explain regular population cycles for many decades delayed density dependence may hold the answer.[2] Here populations are allowed to increase above their normal capacity because there is a time lag until negative feedback mechanisms bring the population back down. This effect has been used to explain the widely fluctuating population cycles of lemmings,[3] forest insects as well as the population cycles of larger mammals such as moose and wolves.[4] Other causes of population cycles include cycling abiotic factors.[5]

Causes

The causes of delayed density dependence vary in each situation. In lemmings, food supply and predation are the most important factors that lead to delayed density dependence.[3] Competition between life stages is another cause. In some species of moth the practice of egg cannibalism takes place where older moths eat eggs of their own species.[6] This produces imbalances in the population levels of different generations leading to delayed density dependence.[6] Disease is another causative factor. The delay is introduced because of the time it takes for enough susceptible individuals to be present for the disease to spread again.[7] The delay to sexual maturity introduces delayed density dependence in many instances. In this case there is density dependent inhibition applied to organisms when they are sexually immature.[8] When this generation reaches sexual maturity there are fewer offspring, continuing the pattern.

Methods of Detection

Autocorrelation is the principal method by which delayed density dependence can be detected. Time series are analysed for repeating patterns.[9]

References

  1. ↑ BONSALL, M.B., HASAN, N. and NAKAMURA, K., 2007. Density dependence and noise determine the long-term dynamics of two species of lady beetle (Coleoptera: Coccinellidae: Epilachninae) in the Indonesian tropics. Ecological Entomology, 32(1), pp. 28-37.
  2. 1 2 TURCHIN, P., TAYLOR, A.D. and REEVE, J.D., 1999. Dynamical role of predators in population cycles of a forest insect: An experimental test. Science, 285(5430), pp. 1068-1071.
  3. 1 2 FRAMSTAD, E., STENSETH, N.C., BJORNSTAD, O.N. and FALCK, W., 1997. Limit cycles in Norwegian lemmings: Tensions between phase-dependence and density-dependence. Proceedings of the Royal Society B: Biological Sciences, 264(1378), pp. 31-38.
  4. ↑ POST, E., STENSETH, N.C., PETERSON, R.O., VUCETICH, J.A. and ELLIS, A.M., 2002. Phase dependence and population cycles in a large-mammal predator-prey system. Ecology, 83(11), pp. 2997-3002.
  5. ↑ HUNTER, M.D. and PRICE, P.W., 2000. Detecting cycles and delayed density dependence: A reply to Turchin and Berryman. Ecological Entomology, 25(1), pp. 122-124.
  6. 1 2 BRIGGS, C.J., SAIT, S.M., BEGON, M., THOMPSON, D.J. and GODFRAY, H.C.J., 2000. What causes generation cycles in populations of stored-product moths? Journal of Animal Ecology, 69(2), pp. 352-366.
  7. ↑ BJØRNSTAD, O.N., SAIT, S.M., STENSETH, N.C., THOMPSON, D.J. and BEGON, M., 2001. The impact of specialized enemies on the dimensionality of host dynamics. Nature, 409(6823), pp. 1001-1006.
  8. ↑ COOKE, K.L., ELDERKIN, R.H. and HUANG, W., 2006. Predator-prey interactions with delays due to juvenile maturation. SIAM Journal on Applied Mathematics, 66(3), pp. 1050-1079.
  9. ↑ (1998). Insect populations in theory and in practice: 19th Symposium of the Royal Entomological Society 10–11 September 1997 at the University of Newcastle. Dordrecht, Kluwer Academic.

See also

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