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Demographic and genetic effects on reproduction as related to population size in a rare, perennial herb,Senecio integrifolius(Asteraceae)

Authors
Journal
Biological Journal of the Linnean Society
0024-4066
Publisher
Wiley Blackwell (Blackwell Publishing)
Publication Date
Volume
50
Issue
3
Identifiers
DOI: 10.1006/bijl.1993.1053
Keywords
  • —Allee Effect - Inbreeding - Genetic Load - Lethal Equivalents
Disciplines
  • Ecology
  • Geography
  • Medicine

Abstract

Abstract Seed-set of the rare and threatened plant Senecio integrifolius increased significantly with population size. Experimental studies as well as field observations showed this to be due to density-dependent seed-set (Allee effect). Hand-pollination revealed lower seed-set, and a lower germination rate of inbred progeny than of outbred progeny, with great differences among populations. Contrary to general predictions in models of minimum viable population sizes, the present study indicates little negative effects of inbreeding in small populations. A genetic load model was invoked to explain the results, hypothesizing that purging of deleterious alleles in small populations has reduced inbreeding depression. However, no clear correlation between population size and genetic load was found. The results in this paper suggest that demographic and environmental factors are of greater immediate importance than population genetics in determining extinction probabilities of small plant populations.

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