Efficiency of selection, as measured by single nucleotide polymorphism variation, is dependent on inbreeding rate in Drosophila melanogaster

Abstract

It is often hypothesized that slow inbreeding causes less inbreeding depression than fast inbreeding at the same absolute level of inbreeding. Possible explanations for this phenomenon include the more efficient purging of deleterious alleles and more efficient selection for heterozygote individuals during slow, when compared with fast, inbreeding. We studied the impact of inbreeding rate on the loss of heterozygosity and on morphological traits in Drosophila melanogaster. We analysed five noninbred control lines, 10 fast inbred lines and 10 slow inbred lines; the inbred lines all had an expected inbreeding coefficient of approximately 0.25. Forty single nucleotide polymorphisms in DNA coding regions were genotyped, and we measured the size and shape of wings and counted the number of sternopleural bristles on the genotyped individuals. We found a significantly higher level of genetic variation in the slow inbred lines than in the fast inbred lines. This higher genetic variation was resulting from a large contribution from a few loci and a smaller effect from several loci. We attributed the increased heterozygosity in the slow inbred lines to the favouring of heterozygous individuals over homozygous individuals by natural selection, either by associative over-dominance or balancing selection, or a combination of both. Furthermore, we found a significant polynomial correlation between genetic variance and wing size and shape in the fast inbred lines. This was caused by a greater number of homozygous individuals among the fast inbred lines with small, narrow wings, which indicated inbreeding depression. Our results demonstrated that the same amount of inbreeding can have different effects on genetic variance depending on the inbreeding rate, with slow inbreeding leading to higher genetic variance than fast inbreeding. These results increase our understanding of the genetic basis of the common observation that slow inbred lines express less inbreeding depression than fast inbred lines. In addition, this has more general implications for the importance of selection in maintaining genetic variation.

Trait specific consequences of fast and slow inbreeding: lessons from captive populations of Drosophila melanogaster

“…This suggests that, in our lines, purging is not more efficient with slower rates of inbreeding. A study of 40 SNP markers showed that our slow inbred lines actually maintain higher levels of molecular variation compared to fast inbred lines despite the same expected level of inbreeding (Demontis et al 2009). This is interesting as it emphasizes that selection acts differently in slow and fast inbred lines.…”

Single nucleotide polymorphism of the growth hormone (GH) encoding gene in inbred and outbred domestic rabbits

“…Several interesting results and analyses have been presented in this line (Kristensen and Sorensen, 2005;Demontis et al, 2009;Ayroles et al, 2009;Paige, 2010;Vermeulen et al, 2013).…”

“…According to most researchers, inbreeding leads to reduced heterozygosity and respectively, lower genetic diversity of populations (Falconer and Mackay, 1996;Кeller, 2002;Charlesworth and Willis, 2009;Nietlisbach et al, 2016;Tanchev, 2016). Some studies and analyses however provide evidence that the process of inbreeding-induced reduction of heterozygous genotypes within a population is multifactorial, although the most influential factors are its size, heterogeneity and the rate of achieving a specific inbreeding level (Maiwashe and Blackburn, 2004;Frankham, 2002;Charlesworth and Charlesworth, 1999;Demontis et al, 2009;Liao and Reed, 2009). Hence, the main purpose of the present study was to investigate the genetic C/T variability of the growth hormone (GH) gene in outbred New Zealand White and inbred synthetic populations of rabbits through PCR-RFLP.…”

Adapting to climate change: a perspective from evolutionary physiology

“…Moreover, although assisted translocation of entire species may be difficult, translocation of genotypes adapted to different conditions is likely to be much more feasible and might provide an insurance policy against future change (Broadhurst et al 2008, Hedrick & Fredrickson 2010, but see Bijlsma et al 2010. In this regard, assessments of movements of individuals into areas perhaps already occupied by other populations of the species may have to move away from the consideration of neutral markers only (which will show differences based mostly on time of isolation) and consider genes that are likely to have significance in the context of environmental responses (Demontis et al 2009, Pertoldi et al 2010. Genome-based evolutionary physiology has much to offer here too.…”