Outbreeding causes developmental instability in Drosophila subobscura

Abstract

A possible effect of interpopulation hybridization is either outbreeding depression, as a consequence of breakdown of coadapted gene complexes which can increase developmental instability (DI) of the traits, or increased heterozygosity, which can reduce DI. One of the principal methods commonly used to estimate DI is the variability of fluctuating asymmetry (FA). We analysed the effect of interpopulation hybridization in Drosophila subobscura through the variability in the wing size and the FA of wing length and width for both sexes in parental, F1 and F2 generations. The results of the wing size per se in intra-and interpopulation hybrids of D. subobscura do not explicitly reveal the significance of either of the two hypotheses. However, the results of the FA of the wing traits give a different insight. The FA of wing length and width generally increases in interpopulation crosses in F1 with respect to the FA in the parental generation, which suggests the possibility that outbreeding depression occurred in the first generation after the hybridization event. We generally observed that the FA values for the wing length and width of interpopulation hybrids were higher in F1 and F2 generations, compared to intrapopulation hybrids in same generations. These results suggest that the association between coadaptive genes with the same evolutionary history are the most probable mechanism that maintains the developmental homeostasis in Drosophila subobscura populations.

Local adaptation at fine spatial scale through chromosomal inversions and mito-nuclear epistasis: Findings in Drosophila subobscura (Diptera: Drosophilidae)

“…We propose that locally adapted alleles within chromosomal inversions forming coadaptive gene complexes, together with joint selection acting on mitochondrial and nuclear genomes, are responsible for the presence of local adaptations to specifi c microhabitats in D. subobscura, despite high gene fl ow. This hypothesis is supported by the signifi cant outbreeding depression reported by Kurbalija et al (2010) in inter-population hybrids from geographically close but environmentally distinct microhabitats. The occurrence of signifi cant outbreeding depression in the F 1 generation could be explained by factors such as underdominance, epistatic interactions or disruption of local adaptations (Edmands, 2007;Escobar et al, 2008) as in the cited study.…”

Temperature‐specific acclimation effects on adult locomotor performance of inbred and crossbredDrosophila melanogaster

“…Inbreeding leads to an increase in homozygosity and, with partial dominance or overdominance, often to inbreeding depression. The fixation of incompatible gene combinations as a result of genetic drift during the inbreeding process is also suggested to partly explain inbreeding depression (Kristensen et al , ; Kurbalija et al , ). All six maze runs where the offspring are reared at 30 °C show heterosis according to the criteria outlined above compared with just one in six runs at each of the two lower temperatures (Table ).…”

Effect of lead pollution on fitness and its dependence on heterozygosity in Drosophila subobscura

“…The results obtained with inversion polymorphism as an adaptive molecular marker suggest that populations in different habitats have been subjected to habitat-specific selection regimes (Stamenkovic-Radak et al 2012). Literature data indicate that D. subobscura populations are genetically diverse (according to putatively adaptive polymorphism), even on a small geographic scale, with frequent strong and unpredictable consequences of interpopulation hybridization (Kurbalija et al 2010). Results for chromosome markers and mtDNA to some extent suggest adaptive population divergence and local adaptation to specific microhabitat characteristics (terrain topology, temperature, humidity, insolation and vegetation coverage).…”

“…The results of hybridization in terms of fitness depend largely on the genetic differences between populations. If they are genetically similar, effects of hybridization may be beneficial; but with increased genetic divergence, hybridization may lead to outbreeding depression, as a result of disruption of local adaptation under-dominance or breakdown of coadapted gene complexes (Edmands 2007;Kurbalija et al 2010).…”

“…In Drosophila, lead pollution affects various fitness components such as development (Cohn et al 1992;Stark and Banks 2003;Kenig et al 2013), longevity, fecundity and even complex behavioural traits such as courtship (Cohn et al 1992;Massie et al 1992;Hirsch et al 2003). On the other hand, studies on the effects of different levels of population heterozygosity on fitness components in many species showed both benefits and outbreeding depression (Tallmon et al 2004;Kurbalija et al 2010).…”