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Inbreeding adversely affects fitness traits in many plant and animal species, and the magnitude, stability and genetic basis of inbreeding depression (ID) will have short- and longterm evolutionary consequences. The effects of four degrees of inbreeding (selfing, f¼50%; full- and half-sib matings, f¼25 and 12.5%; and unrelated outcrosses, f¼0%) on survival and growth of an island population of Eucalyptus globulus were studied at two sites for over 14 years. For selfs, ID in survival increased over time, reaching a maximum of 49% by age 14 years. However, their inbreeding depression for stem diameter remained relatively stable with age, and ranged from 28 to 36% across years and sites. ID for survival was markedly greater on the more productive site, possibly due to greater and earlier onset of inter-tree competition, but was similar on both sites for the diameter of survivors. The deleterious trait response to increasing inbreeding coefficients was linear for survival and diameter. Nonsignificant quadratic effects suggested that epistasis did not contribute considerably to the observed ID at the population level. Among- and within-family coefficients of variation for diameter increased with inbreeding degree, and the variance among the outcrossed families was significant only on the more productive site. The performance of self-families for diameter was highly stable between sites. This suggests that, for species with mixed mating systems, environmentally stable inbreeding effects in open-pollinated progenies may tend to mask the additive genotype-by-environment interaction for fitness traits and the adaptive response to the environment. Heredity (2011) 107, 50–60; doi:10.1038/hdy.2010.154; published online 12 January 2011

Item Type:	Refereed Article
Keywords:	outcrossing; selfing; inbreeding depression; additive and non-additive genetic effects; genotype-by-environment interaction; age trends
Research Division:	Agricultural, Veterinary and Food Sciences
Research Group:	Forestry sciences
Research Field:	Tree improvement (incl. selection and breeding)
Objective Division:	Plant Production and Plant Primary Products
Objective Group:	Forestry
Objective Field:	Hardwood plantations
UTAS Author:	Tilyard, P (Mr Paul Tilyard)
UTAS Author:	Potts, BM (Professor Brad Potts)
ID Code:	72171
Year Published:	2011
Web of Science® Times Cited:	33
Deposited By:	Plant Science
Deposited On:	2011-08-23
Last Modified:	2017-11-09
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