Inter-population variation in male mating behaviours in the sailfin mollie, Poecilia latipinna

Male sailfin mollies show size-dependent variation in sexual behaviour. The level of variation between six north Florida populations in rates of condition-dependent behaviours was estimated and whether behavioural variation is ordered with respect to male body size distributions was determined. In five of six populations, courtship display rates increased with male length, supporting previous evidence. Several results were not consistent with those reported elsewhere. Rates of gonopodial thrusting and gonoporal nibbling were not related to male body length. Courtship display rates adjusted for male body size were not ordered with respect to male body size distributions. High adjusted courtship rates were characteristic of populations where males were predominantly large and where they were predominantly small. No consistent pattern of variation existed between populations in the relationships of the three behaviour patterns to one another. Variation between populations in size-dependent behaviour is therefore far more extensive but less patterned than previously reported. These results imply that evolution can adjust the rates of the three behaviour patterns both independently of one another and of body size, and that the direction of behavioural evolution is not likely to be constrained by covariances within any single natural population. (C) 1996 The Association for the Study of Animal Behaviour.