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Life cycle expression of inbreeding depression in Eucalyptus regnans and intergenerational stability of its mixed mating system


Griffin, AR and Potts, BM and Vaillancourt, RE and Bell, JC, Life cycle expression of inbreeding depression in Eucalyptus regnans and intergenerational stability of its mixed mating system, Annals of Botany, 124, (1) pp. 179-187. ISSN 0305-7364 (2019) [Refereed Article]

Copyright Statement

Copyright 2019 the authors

DOI: doi:10.1093/aob/mcz059


Background and Aims: Many plants exhibit a mixed mating system. Published models suggest that this might be an evolutionarily stable rather than a transitional state despite the presence of inbreeding depression, but there is little empirical evidence. Through field experimentation, we studied the role of inbreeding depression in eliminating inbred progeny from the reproductive cohort of the forest tree Eucalyptus regnans, and demonstrate a stable mixed primary mating system over two successive generations.

Methods: Two field experiments were conducted using seed from natural populations. We sowed open-pollinated seeds to simulate a natural regeneration event and determined isozyme genotypes of dominant and suppressed individuals over 10 years. We also planted a mixture of open-pollinated, outcross and selfed families with common maternal parentage; monitored survival of cross types over 29 years; and determined the percentage of outcrosses in open-pollinated seed from a sample of reproductively mature trees using microsatellite analysis.

Key Results: Both experiments demonstrated progressive competitive elimination of inbred plants. By 29 years, the reproductive cohort in the planted experiment consisted only of outcrosses which produced seed which averaged 66 % outcrosses, similar to the estimate for the parental natural population (74 %).

Conclusions: Selective elimination of inbred genotypes during the intense intra-specific competition characteristic of the pre-reproductive phase of the life cycle of E. regnans results in a fully outcrossed reproductive population, in which self-fertility is comparable with that of its parental generation. The mixed mating system may be viewed as an unavoidable consequence of the speciesí reproductive ecology, which includes the demonstrated effects of inbreeding depression, rather than a strategy which is actively favoured by natural selection.

Item Details

Item Type:Refereed Article
Keywords:Eucalyptus regnans, forest trees, inbreeding, mixed mating, outcrossing rate, demography, genetic structure
Research Division:Biological Sciences
Research Group:Genetics
Research Field:Genetics not elsewhere classified
Objective Division:Plant Production and Plant Primary Products
Objective Group:Forestry
Objective Field:Native forests
UTAS Author:Griffin, AR (Professor Rod Griffin)
UTAS Author:Potts, BM (Professor Brad Potts)
UTAS Author:Vaillancourt, RE (Professor Rene Vaillancourt)
ID Code:134309
Year Published:2019
Web of Science® Times Cited:7
Deposited By:Plant Science
Deposited On:2019-08-07
Last Modified:2020-08-07

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