Lifespan, interbreeding, and social context: the effects on Drosophila melanogaster.

Chromosomal differences in the heterogametic sex (XY or ZW) of organisms has been suggested to lead to a greater quantity of recessive, potentially maladaptive, allele expression in the heterogametic sex compared to the homogametic sex (XX or ZZ), this is known as the unguarded-X hypothesis (Sultanova et al. 2018). One of the key features of the unguarded-X hypothesis is that when inbreeding occurs in will have a greater effect on the lifespan of the homogametic sex compared to the heterogametic sex, due to increasing the expressed frequency of maladaptive recessive mutations in the homogametic sex, as any maladaptive recessive mutations would already be expressed in the heterogametic sample (Sultanova et al. 2018).

Through the use of different inbreeding scenarios (inbred, partially inbred, and outbred) Sultanova et al. (2018) investigated the effects of inbreeding on male and female lifespan and fitness, in relation to social context in flies (specifically Drosophila melanogaster). The social contexts used were isolation, single sex groups, and mixed sex groups (Sultanova et al. 2018).

It was generally found that inbreeding reduced the lifespan of flies, and that the lifespans of female flies were greatly shortened compared to the male flies when they were inbred (Sultanova et al. 2018). However, it should be noted that inbred female reduction in lifespan occurred in all social contexts, but that in inbred males the reduced lifespan was observed in the isolation and single sex groups, and not in the mixed sex groups (Sultanova et al. 2018). It should also be noted that there was no observed positive effect on fitness to counterbalance the negative effect of inbreeding on lifespan (Sultanova et al. 2018). However, these results do not exactly match those of other studies looking at other species of organism, which Sultanova et al. (2018) suggest indicates differences in the genetic architecture related to lifespan across species.

As Sultanova et al. (2018) note this illustrates that the issue of how genetic variation relates to lifespan length across species is a complex matter where further research is needed.

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References

Sultanova, Z., Andic, M., and Carazo, P., 2018. The “unguarded-X” and the genetic architecture of lifespan: Inbreeding results in a potentially maladaptive sex-specific reduction of female lifespan in Drosophila melanogaster. Evolution. 72: 540-552.

Image: WellGenetics Inc., 2018. Drosophila CRISPR genome editing services. https://wellgenetics.com/genomeediting.html Accessed 04/02/18

Victoria Lockwood