Date Published: December 16, 2009
Publisher: Public Library of Science
Author(s): Jörg U. Ganzhorn, Summer Arrigo-Nelson, Sue Boinski, An Bollen, Valentina Carrai, Abigail Derby, Giuseppe Donati, Andreas Koenig, Martin Kowalewski, Petra Lahann, Ivan Norscia, Sandra Y. Polowinsky, Christoph Schwitzer, Pablo R. Stevenson, Mauricio G. Talebi, Chia Tan, Erin R. Vogel, Patricia C. Wright, Dennis Marinus Hansen. http://doi.org/10.1371/journal.pone.0008253
Abstract: The ecological factors contributing to the evolution of tropical vertebrate communities are still poorly understood. Primate communities of the tropical Americas have fewer folivorous but more frugivorous genera than tropical regions of the Old World and especially many more frugivorous genera than Madagascar. Reasons for this phenomenon are largely unexplored. We developed the hypothesis that Neotropical fruits have higher protein concentrations than fruits from Madagascar and that the higher representation of frugivorous genera in the Neotropics is linked to high protein concentrations in fruits. Low fruit protein concentrations in Madagascar would restrict the evolution of frugivores in Malagasy communities.
Partial Text: Primate communities of Madagascar are known for the paucity of frugivorous species. In contrast, the high representation of frugivores but under-representation of truly folivorous vertebrates in the Neotropics has been a long-standing enigma in ecology –. Neotropical primate communities (often used as proxy for mammal communities in general , , ), contain more frugivorous genera and species when compared to the Old World primate radiations of Africa/Asia, and these in turn have more frugivores than primate communities of Madagascar , . Explanations for the different numbers of frugivores and folivores include phenological patterns of food resources and plant species diversity. First, it has been postulated for the Neotropics, that young leaves are rare at the time of year when fruit abundance is low. This makes it unlikely that species in the Americas can fall back on young leaves during times of fruit shortage  and does not favor the evolution of folivores. Second, food plant diversity, and in particular the regional species richness of figs as keystone fruit trees during times of food shortage, has been linked to the diversity of frugivores , . Madagascar has very few species of figs and fruit production is erratic due to high climatic stochasticity –. Thus, both factors may contribute to the paucity of frugivores in Madagascar though the generalization of both hypotheses has been questioned and modified by analyses of extended datasets –.
The nitrogen concentrations in ripe fruits were significantly lower at sites in Madagascar than in the Neotropics (Madagascar: 1.09±0.28%, n = 9 sites; Neotropics: 1.37±0.29%, n = 14 sites; MWU-test: z = 2.49, p = 0.011; Fig. 1; Table 1).
On average, protein concentrations in the vegetable food of primates do not differ between regions. This indicates, that the protein requirements of species from different radiations are independent of their phylogenetic history, even though some of the strepsirhine primates of Madagascar can have reduced metabolic rates , . In contrast to the overall vegetable food composition, fruits in the Neotropics and in Madagascar vary in their nitrogen concentrations. This pattern is not due to different sample size, since, despite the fact that fruits have been sampled most comprehensively in Madagascar, the larger number of samples per site does not lower the average protein concentration when compared to the fruits eaten most frequently (Table 3). Thus, the differences between regions are unlikely due to sampling artifacts.