No evidence for optimal fitness at intermediate levels of inbreeding in Drosophila melanogaster

Abstract

Optimal outbreeding theory predicts fitness benefits to intermediate levels of inbreeding. In the present study, we test for linear (consistent with inbreeding depression) and nonlinear (consistent with optimal outbreeding) effects of inbreeding on reproductive fitness in male and female Drosophila melanogaster. We found linear declines in fitness associated with increased inbreeding for egg-to-adult viability, but not the number of eggs laid or sperm competitive ability. Egg-to-adult viability was also lower in the progeny of inbred males and females mated to unrelated individuals. However, there was no evidence for optimal fitness at intermediate levels of inbreeding for any trait. The present study highlights the importance of considering biologically realistic levels of inbreeding and cross-generational effects when investigating the costs and benefits of mating with relatives.

Kin recognition inDrosophila: the importance of ecology and gut microbiota

“…It seems that two types of cues are used by D. melanogaster to determine their investment in copulation, the first related to the food eaten during development, ultimately linked to gut bacteria alteration, and the second, relatedness. Our surprising result that gut bacteria masked kin recognition based on relatedness supports the idea that the risk of inbreeding may be low in this species (Tan et al, 2012) or that the costs associated with inbreeding are not high enough to promote the evolution and/or maintenance of inbreeding avoidance through kin recognition (Robinson et al, 2009;Ala-Honkola et al, 2011). This is also supported by the level of polyandry exhibited by this species, with females remating every3-5 days (Markow, 1996(Markow, , 2002.…”

“…D. melanogaster is a generalist fruit fly species feeding on various fruit sources (Lutz, 1914;Evans, 1916;Jaenike, 1983;Lachaise et al, 1988;Miller et al, 2011), whose female are polyandrous, remating every 3-5 days (Markow, 1996(Markow, , 2002. Although we expect some inbreeding costs in the monandrous species and the species living in dense aggregations, these costs are less clear and results are somewhat contradictory in D. melanogaster Richardson, 1974, 1976;Tompkins and Hall, 1984;Spiess, 1987;Robinson et al, 2009Robinson et al, , 2012Ala-Honkola et al, 2011;Tan et al, 2012). Our study aims at testing simultaneously whether Drosophila have evolved kin recognition according to their ecologies and how this could be influenced by bacteria variations associated with food specificities.…”

“…Adults expressed a strong homogametic preference in mates presenting similarities in their odours, and gut bacteria were directly implicated in the recognition process. In D. melanogaster, various studies have attempted to test its ability to both recognise kin and avoid inbreeding (Spiess, 1987;Mack et al, 2002;Robinson et al, 2009Robinson et al, , 2012Tan et al, 2012), but controversies remain. It is clear that mating with related individuals leads to inbreeding costs, but uncertainty remains on the costs/benefits associated with mating with individuals of varying degrees of relatedness.…”

Assortative mating for relatedness in a large naturally occurring population of Drosophila melanogaster

“…Another possibility is that offspring produced by more closely related pairs suffered lower egg‐to‐adult survival due to inbreeding depression. In a previous laboratory study investigating similar levels of inbreeding in pedigrees derived from this population we found significant linear inbreeding depression for egg‐to‐adult viability (Robinson et al. , 2009), making the later scenario probable.…”

Incestuous Sisters: Mate Preference for Brothers over Unrelated Males in Drosophila melanogaster

“…Whether observed mate preference may cause inbreeding depression in D. melanogaster is not clear yet. Robinson and colleagues [44], [61] found a negative relationship between the degree of genetic similarity within a pair and both egg-to-adult-viability and number offspring at emergence. Increased relatedness also decreased male ability to secure a mating when competing with non-inbred males [62].…”