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Population variation and individual maximum size in two leech populations: energy extraction from cannibalism or niche widening?
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
2013 (English)In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 172, no 1, 119-127 p.Article in journal (Refereed) Published
Abstract [en]

The theory of cannibal dynamics predicts a link between population dynamics and individual life history. In particular, increased individual growth has, in both modeling and empirical studies, been shown to result from a destabilization of population dynamics. We used data from a long-term study of the dynamics of two leech (Erpobdella octoculata) populations to test the hypothesis that maximum size should be higher in a cycling population; one of the study populations exhibited a delayed feedback cycle while the other population showed no sign of cyclicity. A hump-shaped relationship between individual mass of 1-year-old leeches and offspring density the previous year was present in both populations. As predicted from the theory, the maximum mass of individuals was much larger in the fluctuating population. In contrast to predictions, the higher growth rate was not related to energy extraction from cannibalism. Instead, the higher individual mass is suggested to be due to increased availability of resources due to a niche widening with increased individual body mass. The larger individual mass in the fluctuating population was related to a stronger correlation between the densities of 1-year-old individuals and 2-year-old individuals the following year in this population. Although cannibalism was the major mechanism regulating population dynamics, its importance was negligible in terms of providing cannibalizing individuals with energy subsequently increasing their fecundity. Instead, the study identifies a need for theoretical and empirical studies on the largely unstudied interplay between ontogenetic niche shifts and cannibalistic population dynamics.

Place, publisher, year, edition, pages
2013. Vol. 172, no 1, 119-127 p.
Keyword [en]
Cannibalism, Population variation, Individual growth, Hump-shaped growth density relationships, Long-term study
National Category
Evolutionary Biology
URN: urn:nbn:se:umu:diva-72703DOI: 10.1007/s00442-012-2468-8ISI: 000317686800011OAI: diva2:627164
Available from: 2013-06-11 Created: 2013-06-10 Last updated: 2013-06-11Bibliographically approved

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Persson, Lennart
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