Signal convergence in fruits: a result of selection by frugivores?

LOMÁSCOLO, SILVIA B.; SCHAEFER, H. MARTIN

Journal of Evolutionary Biology

Wiley-Blackwell Publishing

Año: 2010 vol. 23 p. 614 - 624

1010-061X

The Dispersal Syndrome hypothesis remains contentious, stating that apparently non-random associations of fruit characteristics result from selection by seed dispersers. We examine a key assumption under this hypothesis, i.e. that fruit traits can be used as reliable signals by frugivores.  We first test this assumption by looking at whether fruit color allows birds and primates to distinguish between fruits commonly dispersed by birds or primates.  Second, we test whether the colors of fruits dispersed by primates are more contrasting to primates than the colors of bird-dispersed fruits, expected if fruit color is an adaptation to facilitate detection by seed dispersers.  Third, we test whether fruit color has converged in unrelated plant species dispersed by similar frugivores.  We use vision models based on peak sensitivities of birds’ and primates’ cone cells.  We base our analyses on the visual systems of two types of birds (violet and ultraviolet-based) and three types of primates (trichromatic primates from the Old and the New Worlds, and a dichromatic New World monkey).  Using a Discriminant Function Analysis, we find that all frugivore groups can reliably discriminate between bird and primate dispersed fruits.  Fruit color can be a reliable signal to different seed dispersers.  However, the colors of primate-dispersed fruits are less contrasting to primates than those of bird-dispersed fruits.  Fruit color convergence in unrelated plants is independent of phylogeny and can be better explained by disperser type, which supports the hypothesis that frugivores are important in fruit evolution.  We discuss adaptive and non-adaptive hypotheses that can potentially explain the pattern we found.