Effects of bottlenecks on quantitative genetic variation in the butterfly Bicyclus anynana

Abstract

The effects of a single population bottleneck of differing severity on heritability and additive genetic variance was investigated experimentally using a butterfly. An outbred laboratory stock was used to found replicate lines with one pair, three pairs and 10 pairs of adults, as well as control lines with approximately 75 effective pairs. Heritability and additive genetic variance of eight wing pattern characters and wing size were estimated using parent-offspring covariances in the base population and in all daughter lines. Individual morphological characters and principal components of the nine characters showed a consistent pattern of treatment effects in which average heritability and additive genetic variance was lower in one pair and three pair lines than in 10 pair and control lines. Observed losses in heritability and additive genetic variance were significantly greater than predicted by the neutral additive model when calculated with coefficients of inbreeding estimated from demographic parameters alone. However, use of molecular markers revealed substantially more inbreeding, generated by increased variance in family size and background selection. Conservative interpretation of a statistical analysis incorporating this previously undetected inbreeding led to the conclusion that the response to inbreeding of the morphological traits studied showed no significant departure from the neutral additive model. This result is consistent with the evidence for minimal directional dominance for these traits. In contrast, egg hatching rate in the same experimental lines showed strong inbreeding depression, increased phenotypic variance and rapid response to selection, highly indicative of an increase in additive genetic variance due to dominance variance conversion.

Genetic Variation and Selection Response in Model Breeding Populations of Brassica rapa Following a Diversity Bottleneck

“…Following a bottleneck, V A has increased for various quantitative traits related to fitness, but decreased in traits with simpler inheritance in several animal experiments (Saccheri et al 2001). No direct evaluations of this kind have been made in plant breeding populations.…”

“…Restrictions in population size have recently been a focus of numerous studies in evolutionary genetics regarding population subdivision and inbreeding (Saccheri et al 2001), founder effects (Goodnight 1988), and domestication (Whitt et al 2002). Following a bottleneck, additive genetic variance (V A ) may increase due to contributions from dominance (Robertson 1952;Willis and Orr 1993) and epistatic variances (Cheverud and Routman 1996;Naciri-Graven and Goudet 2003), in particular for traits closely related to fitness (Zhang et al 2004).…”

What keeps ‘living dead’ alive: demography of a small and isolated population of Maculinea (= Phengaris) alcon

“…Apart from its sheer size, strong isolation and resource limitation as discussed above, it apparently suffers from low genetic diversity, suggesting genetic drift due to isolation and/or that it underwent a prolonged bottleneck or possibly even a series of such events in the past (Saccheri et al 2001). One potential consequence of reduced genetic diversity is low adaptability to changing environmental conditions, e.g.…”

Consequences of fragmentation for the ability to adapt to novel environments in experimental Drosophila metapopulations

“…As a consequence, research into the adaptive response of subdivided populations to environmental challenges is of major importance for conservation biology. Recent studies on plants, butterflies and Drosophila have shown that the adaptive response generally decreases with increasing levels of inbreeding, e.g., due to a pronounced reduction of the effective population size (Frankham et al 1999;Whitlock and Fowler 1999;Saccheri et al 2001;Reed et al 2003;Bouzat 2005, 2006;Briggs and Goldman 2006). However, except for a few (Frankham et al 1999;Willi and Hoffmann 2009), most of these studies involve the adaptive response for quantitative characters that under natural conditions are not, or only peripherally, related to fitness.…”