The correlated evolution of fruit size and color in Ficus (Moraceae) supports the dispersal syndrome hypothesis

LOMÁSCOLO, SILVIA B.; SPERANZA, PABLO; KIMBALL, REBECCA T.

Miami, Florida

Congreso; Association for Tropical Biology and Conservation Annual Meeting; 2004

Association for Tropical Biology and Conservation

The influence of seed dispersers in the evolution of fruiting plants has often been questioned by studies of fruit evolution.  Most such studies, however, have failed to take into account the phylogenetic history of the plants under study, which may confound fruit variation due to common ancestry with adaptive variation; have used inefficient means of controlling for phylogenetic history, such as focusing on conservative taxonomic levels; or have ignored traits that are important for fruit recognition by frugivores, such as fruit color.  We are testing the hypothesis that fruit traits evolve in response to the selective pressure of seed dispersers.  Under this hypothesis, we predict the existence of two dispersal syndromes, which we define as sets of fruit traits that appear together more often that expected by chance.  (1) Mammal Syndrome fruits should be dull-colored and large, because mammals are commonly nocturnal and rely more heavily on olfaction than on visual cues for finding fruits, and because they have teeth, which allows them to eat fruits piecemeal.  (2) Bird Syndrome fruits should be brightly colored and small, because birds are mostly diurnal and have acute color vision, and because they lack teeth and commonly swallow fruits whole.  We performed a comparative analysis on 57 species of Ficus (Moraceae) from the Old World tropics.  Our analysis was done on a phylogeny based on molecular and morphological data.  Data on fruit traits were obtained from published sources and in the field.  Preliminary results from a Correlated Changes test support the existence of dispersal syndromes as defined above and suggest that seed dispersers may shape fruit evolution.  Alternative hypotheses and suggestions for more accurate measurements of fruits traits are discussed.