Fruiting and Fitness in Crataeugs Monogyna: The Effects of Frugivores and Seed Predators

Abstract

The factors influencing variation in the rates of loss of fruit from Crataegus monogyna individuals are examined for one population near Liverpool, England. In contrast to the expectations from optimal foraging theory, there appears to be no simple relationship between fruit abundance and the activities of frugivores. A number of factors may influence rates of fruit loss including: bush width; inter-bush distance; the damage caused by seed predators. Because of correlation between fruiting characters there is a weak relationship between numbers of fruit and their consumption by frugivores. Fruit on larger, more fecund bushes also suffer high rates of seed predation. The outcome of opposing selective influences may be that fruit on smaller bushes have higher fitness. Fluctuations in frugivore and predator abundance may help maintain the observed high variance in fruit characters.