Reproductive effort in two subtidal populations of the limpet, Patelloida mufria

The reproductive cycle and reproductive effort (RE) of 2 populations of the acmaeid limpet Patelloida mufria were investigated in a subtidal region of N.S.W., Australia. These two populations had vastly different densities, rates of growth and mortality. Nonetheless, their patterns of spawning were remarkably similar with 5 spawning periods during the year of monitoring, and their values for RE were very similar; individuals from each population spawned about 35% of their somatic weight each 6 months. This does not, therefore, conform with theories that the RE of populations should be correlated with their rates of mortality. The results for P. mufria were compared with those of 4 populations of Cellana tramoserica and 2 of P. alticostata which had been studied previously at this location. There was still no general correlation between RE and mortality, but by only using certain combinations of these 8 populations (i.e. only one from each species at a time), positive or negative correlations could be obtained. This illustrated the need to ensure that intraspecific variability is accounted for in any analysis of life-history strategies. Finally, it was concluded that instead of the absolute vale of RE being important, the amount of flexibility in this and other traits may represent the real difference in strategies amongst species.