Question: Is there evidence for limiting similarity in the timing of fruit production by a bird-dispersed plant community? Is the rate of fruit removal in each plant species inversely related to fruit availability in other species? Can simple measurements of fruit phenologies (i.e. temporal changes in fruit availability) obscure important fruit attributes that influence their removal by birds?
Location: Vancouver Island, British Columbia, Canada.
Methods: Periods of fruit availability were measured in ten woody angiosperm species for two years. In the second year, the fate of individual fruits was quantified to disentangle dates of fruit maturation, removal and mortality from measurements of availability.
Results: Null model analyses of fruit availability distributions showed no evidence for limiting similarity. However, fruit removal rates of most plant species were correlated with their relative abundance in the community, indicating fruits were removed more rapidly when other fruits were less abundant. Species with similar periods of fruit availability often had different dates of fruit maturation, rates of fruit removal and fruit persistence times, indicating fruit availability measurements can obscure important bird-fruit interactions.
Conclusions: Competition for dispersers appears to occur. However, it has not resulted in limiting similarity in fruit availability distributions. A likely explanation for this discrepancy is that fruit availability distributions often confound several important fruit attributes that can independently influence fruit removal by birds.
Nomenclature: Hitchcock & Cronquist (1994).