SLIDE 3 Heredity (1996) 76, 83–91; doi:10.1038/hdy.1996.11
Variation in inbreeding depression among families and populations of Clarkia tembloriensis (Onagraceae)
Timothy P Holtsford1
1Division of Biological Sciences, University of Missouri, Columbia, MO 65203, USA
Received 9 June 1995. Top
Abstract The relationship between the self-fertilization rate of a population and the severity of inbreeding depression is difficult to predict because the underlying genetics may be complex. However, it is important to understand this relationship, and the degree to which inbreeding depression varies among families within populations, if we are to understand the evolution of plant mating systems. Inbreeding depression was studied in glasshouse trials using seed derived from two populations of Clarkia tembloriensis, Cantua Creek and Idria. These had very different rates of self-fertilization (s) and inbreeding coefficients (F) (s = 0.74, F = 0.77 in the CC-1 population; 5 = 0.16, F = 0.10 in the I-1 population). Outcrossing between these populations was equivalent to outcrossing within them; there was no evidence for outbreeding depression or increased heterosis from interpopulation
- crosses. The more self-fertilizing CC-1 population had fewer recessive lethal genes than the
- utbreeding I-1 population. However, cumulative inbreeding depression at the end of flowering was
not significantly different between these populations. Inbreeding has seemingly purged the lethal genes from the CC-1 population but overall mutational load, especially in characters that are manifest late in the life history, is still substantial despite a history of inbreeding. Variation in inbreeding depression among families within these two populations was surprisingly large. The range
- f variation among families was five to seven times larger than the difference in inbreeding
depression between populations. Variation in inbreeding depression among families should make these populations more susceptible to the invasion of genes which increase the rate of self- fertilization.
Keywords: Clarkia, inbreeding depression, mating system, self-fertilization
Colonial naked mole rats do not show much inbreeding depression
VIRAL EPIZOOTIC REVEALS INBREEDING DEPRESSION IN A HABITUALLY INBREEDING MAMMAL
Adin Ross-Gillespie 1,2,3 , M. Justin O'Riain 1 , and Lukas F. Keller 4 1 Department of Zoology, University of Cape Town, Rondebosch 7700, South Africa 2 E-mail: A.Ross-Gillespie@ed.ac.uk 4 Zoologisches Museum, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland Correspondence to 3 Present address: Institute of Evolutionary Biology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, United Kingdom. Associate Editor: H. Kokko Correspondence to 3 Present address: Institute of Evolutionary Biology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, United Kingdom. KEYWORDS Coronavirus • disease susceptibility • Heterocephalus glaber • inbreeding depression • purging ABSTRACT Inbreeding is typically detrimental to fitness. However, some animal populations are reported to inbreed without incurring inbreeding depression, ostensibly due to past "purging" of deleterious alleles. Challenging this is the position that purging can, at best, only adapt a population to a particular environment; novel selective regimes will always uncover additional inbreeding load. We consider this in a prominent test case: the eusocial naked mole-rat (Heterocephalus glaber), one of the most inbred of all free-living mammals. We investigated factors affecting mortality in a population of naked mole-rats struck by a spontaneous, lethal coronavirus outbreak. In a multivariate model, inbreeding coefficient strongly predicted mortality, with closely inbred mole-rats (F 0.25) over 300% more likely to die than their outbred counterparts. We demonstrate that, contrary to common assertions, strong inbreeding depression is evident in this
- species. Our results suggest that loss of genetic diversity through inbreeding may render populations vulnerable to local extinction from
emerging infectious diseases even when other inbreeding depression symptoms are absent. Received January 29, 2007 Accepted May 8, 2007 DIGITAL OBJECT IDENTIFIER (DOI) 10.1111/j.1558-5646.2007.00177.x
Predicting inbreeding depression
Scenario
What is the chance of suffering “Inbreeding depression” when mating with close relatives
Genetic load Large population High
(large number of rare semilethal alleles)
Low Recently small population Intermediate
(purged some detrimentals of large effect)
Intermediate
(fixed some detrimentals with small effect)
Long-term small population Low
(purged detrimentals of medium or large effect)
High
(fixed many detrimentals with small effect) Genetic load = Reduction of the mean fitness resulting from detrimental variation for a population compared to a population without lowered fitness.
Hedrick, P. W. 2001. Conservation Genetics: where are we now? Trends in Ecology and Evolution 16:629-636
Inbreeding avoidance
Plants Self-incompatiblity Male and female parts flower at different times Heterostyly (females and male parts are far from each
Male and females are different plants Animals Mate choice (mice smell whether they belong to the same MHC type or not) Migration behavior (Young lions get driven from their pack)
Larkspur Delphinium nuttallianum
0.08 a 30 0.65 b 10 0.42 b 3 0.30 a 1 Overall fitness Distance between parents (m)
