ANGIOSPERM FLESHY FRUITS AND SEED DISPERSERS - A COMPARATIVE-ANALYSISOF ADAPTATION AND CONSTRAINTS IN PLANT-ANIMAL INTERACTIONS

Variation in phenotypic traits of angiosperm fleshy fruits has been ex plained as the result of adaptations to their mutualistic seed dispers ers. By analyzing the information available on fleshy fruit characteri stics of 910 angiosperm species, I assess the hypothesis of evolutiona ry association between fruit phenotypic traits and type of seed disper ser (birds, mammals, and mixed dispersers) and address explicitly and quantitatively alternative null hypotheses about phylogenetic effects. Phylogenetic affinity among plant taxa is accounted for by comparativ e methods including nested ANOVA, phylogenetic autocorrelation, and in dependent contrasts. Averaging over the 16 fruit traits examined, phyl ogenetic effects down to genus level explain 61% of total variance. Ph ylogenetic autocorrelations are strong among close relatives, reaching significance for II of the 16 fruit traits examined. When assessed by independent contrast methods, correlated evolution between type of di sperser and fruit traits is confined to fruit diameter. Differences am ong dispersal syndromes in other traits vanish after accounting for ph ylogenetic effects. These analyses reveal that seed dispersal syndrome s are not entirely interpretable as current adaptations to seed disper sers. Their status as exaptations can be assessed by combining experim ental studies of natural selection on fruit size and rigorous comparat ive and cladistic tests of adaptational hypotheses.