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[edit]
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[edit]
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[edit]
Autocorrelation is the principal method by which delayed density dependence can be detected. Time series are analysed for repeating patterns.[9]
See also[edit]
References[edit]
- ^ 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.
- ^ a b 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.
- ^ a b 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.
- ^ 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.
- ^ 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.
- ^ a b 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.
- ^ 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.
- ^ 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.
- ^ (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.