Maintenance of Fertility in the Face of Meiotic Drive

Abstract

Selfish genetic elements that gain a transmission advantage through the destruction of sperm have grave implications for drive male fertility. In the X-linked SR meiotic drive system of a stalk-eyed fly, we found that drive males have greatly enlarged testes and maintain high fertility despite the destruction of half their sperm, even when challenged with fertilising large numbers of females. Conversely, we observed reduced allocation of resources to the accessory glands that probably explains the lower mating frequency of SR males. Body size and eyespan were also reduced, which are likely to impair viability and precopulatory success. We discuss the potential evolutionary causes of these differences between drive and standard males.

Selfish genetic elements and male fertility

“…In some taxa, sperm death is compensated by increased production (e.g. stalk-eyed fly, Teleopsis dalmanii) [46,47].…”

Meiotic drive does not cause condition‐dependent reduction of the sexual ornament in stalk‐eyed flies

“…This is associated with extended lifespan and the production of additional litters in later life (Ferrari et al., 2019). These life history changes contrast with resistance to drive and female polyandry because they enhance the fitness and spread of the meiotic driver itself (Meade et al., 2020). There are parallels here to alterations in host behaviour associated with other selfish genetic elements such as Wolbachia , though it is often unclear whether changes are detrimental or beneficial to host fitness (Awrahman et al., 2013; Wedell, 2019).…”

“…The allocation of increased resources to testes presumably means that SR males have less to invest in other traits. This may explain the reduced accessory gland size of SR males, as testes and accessory glands develop over a period of several weeks post‐eclosion (Baker et al., 2003; Meade et al., 2020; Rogers et al., 2008). It is less obvious why increased investment in testes constrains eyespan development, as the latter reflects pre‐eclosion resource allocation.…”

“…A meiotic drive stock was obtained in 2012 by Sam Cotton from the same Ulu Gombak location. Meiotic drive is maintained following a standard protocol (Meade et al., 2020; Presgraves et al., 1997). Briefly, females heterozygous for SR (X SR X ST ) are crossed to ST (X ST Y) males and the female offspring are discarded.…”

“…Comp162710 is an indel marker developed in the laboratory of Jerry Wilkinson (personal communication) to identify X SR chromosomes that carry a small allele (201 bp) and X ST chromosomes that carry a large allele (286 bp). This marker has been successfully used previously (Meade et al., 2020). Comp167210 fragment lengths were assayed by gel electrophoresis on a 3% agarose gel with a 0.5× TBE buffer.…”