Effects of inbreeding on aversive learning in Drosophila

Abstract

Inbreeding adversely affects life history traits as well as various other fitness‐related traits, but its effect on cognitive traits remains largely unexplored, despite their importance to fitness of many animals under natural conditions. We studied the effects of inbreeding on aversive learning (avoidance of an odour previously associated with mechanical shock) in multiple inbred lines of Drosophila melanogaster derived from a natural population through up to 12 generations of sib mating. Whereas the strongly inbred lines after 12 generations of inbreeding (0.75 < F < 0.93) consistently showed reduced egg‐to‐adult viability (on average by 28%), the reduction in learning performance varied among assays (average = 18% reduction), being most pronounced for intermediate conditioning intensity. Furthermore, moderately inbred lines (F = 0.38) showed no detectable decline in learning performance, but still had reduced egg‐to‐adult viability, which indicates that overall inbreeding effects on learning are mild. Learning performance varied among strongly inbred lines, indicating the presence of segregating variance for learning in the base population. However, the learning performance of some inbred lines matched that of outbred flies, supporting the dominance rather than the overdominance model of inbreeding depression for this trait. Across the inbred lines, learning performance was positively correlated with the egg‐to‐adult viability. This positive genetic correlation contradicts a trade‐off observed in previous selection experiments and suggests that much of the genetic variation for learning is owing to pleiotropic effects of genes affecting functions related to survival. These results suggest that genetic variation that affects learning specifically (rather than pleiotropically through general physiological condition) is either low or mostly due to alleles with additive (semi‐dominant) effects.

Effect of Inbreeding on Host Discrimination and Other Fitness Components in a Seed Beetle

“…One might predict that a complex behavior would be especially susceptible to inbreeding depression because phenotypic variation in behavior is commonly determined by nonadditive genetic effects, with strong dominance and/or epistasis (Meffert et al 2002, Mackay 2009). However, Nepoux et al (2010) found that moderate inbreeding (F ϭ 0.375) in Drosophila had no effect on two behavioral traits, aversive learning or odor responsiveness, even though it was sufÞcient to reduce egg-to-adult viability. They speculated that the absence of inbreeding depression for learning was a consequence of mostly additive-genetic variation and stabilizing selection.…”

“…They found no consistent decline in egg dispersion among four inbred lines, although there was considerable variation among lines. Their experimental design could not rule out a confounding effect of purging, however, in which the serial inbreeding used to generate inbred lines selectively eliminates deleterious recessive alleles from the population (see Nepoux et al 2010). As a consequence, the genetic load (and thus the estimate of inbreeding depression) in the test generation may have substantially underestimated the genetic load present in the initial outbred population.…”

Influence of Inbreeding on Female Mate Choice in Two Species of Drosophila

“…In a study of Drosophila melanogaster , inbred flies were less responsive to training to avoid certain odors than outbred ones and this effect may have arisen from reduced olfactory ability (Nepoux et al 2010). If females that are less perceptive make faster decisions the trend in the time taken for inbred and outbred females to choose is consistent with this hypothesis.…”

One generation of inbreeding does not affect covering behavior of the sea urchinStrongylocentrotus intermedius

“…Bleakley et al 2006;Mariette et al 2006) and invertebrates (e.g. Nepoux et al 2010;Stone 2012) have been playing an increasingly important role in revealing genetic mechanisms of biological phenomena (Bleakley et al 2006). Despite a number of publications on inbreeding depression in immune (Coffaro & Hinegardner 1977), morphological, and physiological traits (Harada et al 2008), to our knowledge, no information is available on the effects of inbreeding on behaviors of sea urchins.…”