Cannibalism and resource competition determine population structure and regulation in experimental guppy populations
(English)Manuscript (preprint) (Other academic)
Cannibalism and intraspecific resource competition, separately or in combination, can be important factors in regulating populations. Cannibalistic voracity and size of offspring have been shown to be two important factors in determining the extent to which cannibalism can regulate a population. We investigated guppy populations originating from two different environments and that differ in cannibalistic voracity and size of offspring. We investigated mechanisms behind density independent and density dependent relationships by varying the availability of juvenile refuges and harvesting of large females. One population (Turure) had a lower total biomass than the other population (Quare) and showed stronger density dependence in the treatments without refuges. In contrast, the Quare population showed a stronger density dependence when refuges were present. We suggest that the presence of refuges decreased cannibalism and increased competition leading to stronger density dependence through decreased fecundity of females and juvenile growth and survival. Harvest of large females decreased cannibalism but decreased reproductive output even more which led to extinctions of the Turure populations when no refuges were present. When refuges were present harvesting had only a small effect related to that few females grew large enough to be harvested.
IdentifiersURN: urn:nbn:se:umu:diva-36130OAI: oai:DiVA.org:umu-36130DiVA: diva2:352122