Can primates and birds differentiate between primate and bird fruits based on color?

LOMÁSCOLO, SILVIA B.; SCHAEFER, H. MARTIN

San José, California

Congreso; Annual Meeting of the Ecological Society of America; 2007

Ecological Society of America

Some researchers think seed dispersers are important for the evolution of fruiting plants, evidenced by the existence of apparently non-random combinations of fruits traits that match the perceptive and foraging abilities of frugivores, and therefore these syndromes are hypothesized to have evolved under the selective pressure of frugivores.  This is called the Dispersal Syndrome Hypothesis, and assumes that fruit syndromes are a signal to "good dispersers", and may render the fruits cryptic to "bad dispersers".But other evolutionary biologists in the field believe that syndromes are determined by phylogeny or plant life form and are not selected by frugivores.Now we're left with conflicting evidence and a controversy in the field of seed dispersal.  We approach the question of whether seed dispersers are important for the evolution of fruiting plants by testing the Dispersal Syndromes Hypothesis. One of the main assumptions of the Dispersal Syndrome Hypothesis is that color is signaling the ripeness of fruits to good seed dispersers, and therefore the specific questions that we need to ask about color are: 1. Can a bird distinguish between "bird fruits" and  "primate fruits"?; and 2. Can a primate distinguish between "bird fruits" and  "primate fruits"? These are the questions that we're trying to answer in this study.  Color was measured using a spectrometer; we used color vision models specific to primates and birds; the color data and the seed disperser data were obtained from the literature and partly from our own data, which makes this the largest reflectance data analyzed to this date; and we controlled for phylogenetic effects with a Phylogenetic Discriminant Function Analysis.Our results indicate that primates and birds can discriminate between bird and primate fruits on the basis of color. This pattern still holds when phylogeny is controlled, both for birds and for primates, still with pretty high accuracy. This is the first time a study has used color vision models of specific seed dispersers to evaluate how fruit color is perceived from the disperser's perspective. If any progress is to be made towards understanding the importance of seed dispersers in the evolution of fruits, then we must measure color from the frugivore's perspective.