DOI: 10.5061/dryad.cf0468k
title: Data from: Ejaculate sperm number compensation in stalk-eyed flies carrying a selfish meiotic drive element

description: Meiotic drive genes cause the degeneration of non-carrier sperm to bias
 transmission in their favour. Males carrying meiotic drive are expected to
 suffer reduced fertility due to the loss of sperm and associated harmful
 side-effects of the mechanisms causing segregation distortion. However,
 sexual selection should promote adaptive compensation to overcome these
 deleterious effects. We investigate this using SR, an X-linked meiotic
 drive system in the stalk-eyed fly, Teleopsis dalmanni. Despite sperm
 destruction caused by drive, we find no evidence that SR males transfer
 fewer sperm to the female’s spermathecae (long-term storage organs).
 Likewise, migration from the spermathecae to the ventral receptacle for
 fertilisation is similar for SR and wildtype male sperm, both over short
 and long time-frames. In addition, sperm number in storage is similar even
 after males have mated multiple times. Our study challenges conventional
 assumptions about the deleterious effects of drive on male fertility. This
 suggests that SR male ejaculate investment per ejaculate has been adjusted
 to match sperm delivery by wildtype males. We interpret these results in
 the light of recent theoretical models that predict how ejaculate
 strategies evolve when males vary in the resources allocated to
 reproduction or in sperm fertility. Adaptive compensation is likely in
 species where meiotic drive has persisted over many generations and
 predicts a higher stable frequency of drive maintained in wild
 populations. Future research must determine exactly how drive males
 compensate for failed spermatogenesis, and how such compensation may
 trade-off with investment in other fitness traits.
description: Sperm allocation with
 variation in female quality.To test for differences
 in sperm allocation by SR and ST males, we examined sperm storage by
 females after a single mating. Males were tested with large and small
 females to test whether sperm allocation varied with female quality.
 Allocation was assessed through counts of sperm stored in the
 spermathecae.Spermathecae.csvSperm movement to the site of fertilisation.We examined sperm that migrated to the ventral receptacle (VR), the site of egg fertilisation, when females were mated to an SR or ST male. Males were tested with large and small females, and the proportion of VR pouches that were filled (contained a sperm) or empty were counted.VR.csvSperm allocation across sequential matings (multiple mating).To examine SR and ST male sperm number across successive matings, sperm allocation was assessed through counts of sperm stored in spermathecae after a male’s first, second, and third mating. In this experiment, we did not vary female size, but selected mid-sized females with eyespan between 5.25mm – 5.95mm.MultipleMating.csvSperm allocation across sequential matings (third mating).To examine sperm number after successive matings, sperm allocation was assessed through counts of sperm stored in spermathecae on a male’s third mating. Females were mid-sized as before.ThirdMating.csv