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Logo of annbotAboutAuthor GuidelinesEditorial BoardAnnals of Botany
 
Ann Bot. 2008 December; 102(6): 1031–1041.
Published online 2008 October 15. doi:  10.1093/aob/mcn195
PMCID: PMC2712411

Limitations to Reproductive Output and Genetic Rescue in Populations of the Rare Shrub Grevillea repens (Proteaceae)

Abstract

Background and Aims

When conserving rare plant species, managers are often faced with small and/or isolated populations displaying low levels of sexual reproduction and genetic variation. One option for reinvigorating these populations is the introduction of genetic material from other sites, but in some cases fitness may be reduced as a result of outbreeding depression. Here the pollination biology of the rare shrub Grevillea repens is studied across its natural range and reproductive responses following cross-pollination among populations are examined to determine factors that may be limiting sexual reproduction and the potential for genetic rescue.

Methods

Pollen manipulation treatments (self-, autogamous self-, cross- and open pollination) were applied to flowers to examine the breeding system and fruit and seed production in five populations of G. repens. Pollen production, presentation and viability were investigated and interpopulation crosses of increasing genetic distance performed among the populations.

Key Results

The study species is self-incompatible and displayed very low natural seed set over two seasons, due partly to low pollen viability in one of the populations. Within-population crossing increased fruit and seed production at some sites, indicating pollinator limitation. Interpopulation crosses further increased reproductive output in one population, suggesting mate limitation, and for this site there was a positive relationship between genetic distance among populations and the size of genetic rescue benefits. However, in other populations there was a decrease in fruit and seed set with increasing genetic distance.

Conclusions

The results highlight that management strategies involving interpopulation crosses can improve reproductive output in small, isolated populations of rare plants, but guidelines need to be developed on a population by population basis.

Key words: Grevillea repens, Proteaceae, genetic rescue, pollination ecology, self-incompatibility, breeding system, interpopulation cross, outbreeding depression, pollinator limitation, mate limitation, resource limitation

Articles from Annals of Botany are provided here courtesy of Oxford University Press