Meiotic drive systems are associated with low frequency chromosomal inversions. These are expected to accumulate deleterious mutations due to reduced recombination and low effective population size. We test this prediction using the “sex-ratio” (SR) meiotic drive system of the Malaysian stalk-eyed fly Teleopsis dalmanni.SR is associated with a large inversion (or inversions) on the X chromosome. In particular, we study eyespan in males carrying the SR chromosome, as this trait is a highly exaggerated, sexually dimorphic trait, known to have heightened condition-dependent expression. Larvae were raised in low and high larval food stress environments. SR males showed reduced eyespan under the low and high stress treatments but there was no evidence of a condition-dependent decrease in eyespan under high stress. Similar but more complex patterns were observed for female eyespan, with evidence of additivity under low stress and heterosis under high stress. These results do not support the hypothesis that reduced sexual ornament size in meiotic drive males is due to a condition-dependent response to the putative increase in mutation load. Instead, reduced eyespan likely reflects compensatory resource allocation to different traits in response to drive-mediated destruction of sperm.  

Experiment_1_data

Raw data from the first experiment. Column A, "ID", refers to the unique identifier assigned to each fly. Column B, "Sex", refers to the sex of the fly, with F denoting females and M denoting males. Column C, "Cross", refers to the parental cross that generated the fly. Cross A was a cross between females heterozygous for SR meiotic drive and males hemizygous for SR drive. Cross B was a cross between females heterozygous for SR meiotic drive and wild-type, standard (ST) males. Column D, "Treatment", refers to the experimental treatment, either "High stress" or "Low stress". Column E, "Egg.date" refers to the date that the egg from which the fly larva hatched was collected and plated onto developmental "egg-lays", in the DD/MM/YYYY format. Column F, "Collection.date", refers to the date that the adult fly eclosed from its pupa and was collected for measurement, in the DD/MM/YYYY format. Column G, "Dev.time", refers to the total development time of the fly, in days. This is number of days between the "Egg.date" and the "Collection.date". Column H, "Measure.date", refers to the date the fly was measured, in the DD/MM/YYYY format. Column I, "Eyespan", refers to the eyespan of the adult fly, in millimetres, measured as the distance between the distal tips of the eyebulbs. Column J, "Thorax" refers to the length of the adult fly's thorax, in millimetres. It is measured from the anterior-most point of the prothorax to a point that that bisects where the posterior pair of legs attach to the thorax. Column K, "Genotype" refers to the genotype of the fly. SRSR denotes females homogygous for SR. SRX denotes females heterozygous for SR, XX denotes females homozygous for the standard ST X chromosome. SRY denotes SR drive males, and XY denotes standard males.

Experiment_2_data

Raw data from the second experiment, where eggs from Cross A and Cross B were combined on egg lays prior to development. Column A, "Individual.ID", refers to the unique identifier assigned to each fly. Column B, "Cage.ID" refers to a unique identifer of the cage in which flies were allowed to develop and eclose. Column C, "Treatment" refers to the experimental treatment, either "Low stress" or "High stress." Column D, "Sex" refers to the sex of the fly, with F denoting females and M denoting males. Column E, "Eyespan", refers to the eyespan of the adult fly, in millimetres, measured as the distance between the distal tips of the eyebulbs. Column F, "Thorax" refers to the length of the adult fly's thorax, in millimetres. It is measured from the anterior-most point of the prothorax to a point that that bisects where the posterior pair of legs attach to the thorax.  Column G, "Egg.date" refers to the date that the egg from which the fly larva hatched was collected and plated onto developmental "egg-lays", in the DD/MM/YYYY format. Column H, "Measure.date", refers to the date the fly was measured, in the DD/MM/YYYY format. Column I, "Genotype" refers to the genotype of the fly. SRSR denotes females homogygous for SR. SRX denotes females heterozygous for SR, XX denotes females homozygous for the standard ST X chromosome. SRY denotes SR drive males, and XY denotes standard males.