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Ecologically Effective Population Sizes

The extinction risks of threatened species have traditionally been assessed by the use of tools of Population Viability Analysis (PVA). Species interactions, however, have seldom been accounted for in PVA:s. The omission of species interactions in risk assessments may lead to mistakes when setting target sizes of populations. Even a slight decrease in the abundance of a species may result in changes in the community structure; in the worst case leading to a highly impoverished community.

Of critical importance to conservation is therefore the question of how many individuals of a certain species that is needed in order to uphold the ecological role of the species and not merely its persistence. In other words, what is the ecologically effective population size of a species or the minimum ecologically viable population?

We use dynamical models of food webs to estimate ecologically effective population sizes.   The questions we address include:

  • How do species characteristics like trophic position, trophic uniqueness and body mass affect the ecologically effective population size of a species?
  • How do web characteristics like species richness and connectance affect ecologically effective population sizes of species?
  • How much do ecologically effective population sizes differ from traditional Minimum Viable Population (MVP) sizes?

Torbjörn Säterberg, Stefan Sellman & Bo Ebenman

Responsible for this page: Alva Curtsdotter

Last updated: 02/18/11