Behavioural variability in marine larvae

Despite increasing recognition of the importance of larval settlement, recent models have concentrated on small and large scale hydrodynamic effects as determinants of larval settlement. Implicit in most of these discussions is the assumption that variability in larval behaviour either does not exist, or is unimportant. We present evidence that this is an inaccurate description of larval behaviour at the time of settlement. There exists considerable variation in behaviour at a number of scales, even under controlled laboratory conditions. For almost all species examined, responses to attractive and discrete stimuli were non‐uniform. The causes of variability in larval behaviour both within and between populations are largely unexplored. We suggest that variable behaviour, in response to discrete stimuli, may be a selectable trait. If so, the manifestation of such variability in individuals within a population is simply the expression of an adaptive trail. By this reasoning, differences in larval behaviour between populations are evidence for varying selective pressures. We conclude with an examination of possible consequences to a population, arising from variable larval behaviour.