Sustained positive consequences of genetic rescue of fitness and behavioural traits in inbred populations of Drosophila melanogaster

Abstract

One solution to alleviate the detrimental genetic effects associated with reductions in population size and fragmentation is to introduce immigrants from other populations. While the effects of this genetic rescue on fitness traits are fairly well known, it is less clear to what extent inbreeding depression and subsequent genetic rescue affect behavioural traits. In this study, replicated crosses between inbred lines of Drosophila melanogaster were performed in order to investigate the effects of inbreeding and genetic rescue on egg‐to‐adult viability and negative geotaxis behaviour—a locomotor response used to measure, e.g. the effects of physiological ageing. Transgenerational effects of outcrossing were investigated by examining the fitness consequences in both the F1 and F4 generation. The majority of inbred lines showed evidence for inbreeding depression for both egg‐to‐adult viability and behavioural performance (95% and 66% of lines, respectively), with inbreeding depression being more pronounced for viability compared with the locomotor response. Subsequent outcrossing with immigrants led to an alleviation of the negative effects for both viability and geotaxis response resulting in inbred lines being similar to the outbred controls, with beneficial effects persisting from F1 to F4. Overall, the results clearly show that genetic rescue can provide transgenerational rescue of small, inbred populations by rapidly improving population fitness components. Thus, we show that even the negative effects of inbreeding on behaviour, similar to that of neurodegeneration associated with physiological ageing, can be reversed by genetic rescue.

Inbreeding-Driven Innate Behavioral Changes in Drosophila melanogaster

“…Considering the genetic basis of behavior, inbreeding could influence the organism's behavior through the accumulation of certain traits over generations. However, very few studies have been conducted on D. melanogaster in this regard, and existing studies are mostly focused on courtship and locomotor activities of adult flies [24][25][26]28,29]. In this study, we demonstrate how different levels of inbreeding influence seven of the key innate behaviors of D. melanogaster.…”

“…However, to maximize genetic heterogeneity, instead of jar-to-jar transfer, progeny of multiple jars was collected and mixed together to create a new jar of a founder population during the whole course of line maintenance (>150 generations). Moreover, most studies in which the effect of inbreeding has been investigated in D. melanogaster indigenously developed and used lines of fruit flies that were maintained under laboratory conditions for many years [27][28][29]. Nevertheless, it is interesting to explore the nature of alleles in inbred flies that have accumulated over generations due to inbreeding.…”

“…Studies in relation to learning and locomotor activity showed more inter-line variations in inbred D. melanogaster [27,28]. However, Jorgensen et al observed a cumulative decline in locomotor activity in the inbred flies compared to outbred flies [29].…”