Differential mating success in populations of seaweed flies (Coelopa frigida)

Abstract

The reproductive success of seaweed flies (Coelopa frigida) was studied in natural populations. The sizes of females, both mothers and those not producing eggs, as well as of the males available to be fathers, were estimated from their wing lengths. The animals were also classified for their genotype at the alcohol dehydrogenase (Adh) locus-a polymorphic locus tightly associated with a large chromosomal inversion. The fathers' genotypes were inferred from the genotypes of the mother and her offspring. Males of different Adh genotypes had different reproductive success. Reproductive success of genotypes was negatively correlated with the mean sizes of males. Differences in the reproductive success of females could be accounted for by their differential egg laying capacity, and is probably not a consequence of their mating behaviour. The incidence of progeny with mixed paternity varied from 20 per cent initially, to about 65 per cent when the animals had been mating for 6 days. It appears from previous work that large males are more successful in laboratory trials, yet under natural conditions genotypes associated with large male size have low mating success. Ways of reconciling these results and their relevance to understanding the inversion polymorphisms are discussed.

Genetic differences in mating success and female choice in seaweed flies (Coelopa frigida)

“…In mass matings female success wa:s homogeneous whereas heterogeneity was observed between genotypes among the results reported here. Furthermore, the pattern of mating was predominantly negatively assortative in the results of Day and Butlin (1987) whereas in the present experiments the flies tended to exhibit positive assortment.…”

“…1985) and larval survival (Butlin et aL, 1984). There is also differential male mating success between genotypes (Butlin et a!., 1982b; and populations exhibit negative assortative mating with respect to the af3 inversion (Day and Butlin, 1987). A recent analysis of mating (Crocker and Day, 1987) suggested that female seaweed flies might be choosing their mates on the basis of inversion genotype, and that there might, in addition, be an element of male choice.…”

Environmental correlates of inversion frequencies in natural populations of seaweed flies (Coelopa frigida)

“…Inversion frequencies in natural populations strongly suggest that the polymorphism is maintained by selection, and laboratory experiments indicate that at least three types of selection may operate: heterokaryotypic advantage in egg to adult viability (Butlin et a!., 1984), variation in development time (Day et a!., 1980), and sexual selection (Butlin et a!., 1982b, Day et a!., 1987. This is therefore a promising system in which to study the connection between environmental parameters and inversion frequencies.…”

Non-random mating in natural populations of the seaweed fly, Coelopa frigida

“…The materials and experimental procedures are fully described in the accompanying paper (Day et a!., 1987).…”

“…Finally, Bateson (1983) (Butlin et aL, 1982a;Day et a!., 1987), and also significant differences in the fecundities of individuals (Butlin et aL, 1985). This report is concerned with a further aspect of reproductionwho mates with whom?…”