MICHELANGELI, FABIAN A. American Museum of Natural History. Central Park West at 79th street. New York, NY 10024. - Fruit dispersal and character evolution in the Neotropical genus Tococa (Melastomataceae).
Tococa is a genus of 45 species of shrubs, small trees and
vines from Neotropical rain forests and savannas. In 39 species the
fruits are dispersed by birds, as it is the case in most other species
in the family. However, a monophyletic group of six species,
restricted to river banks and flooded forests of the Amazonas and
Orinoco basins, have fruits that are dispersed by either water or fish
(ichthyochory). Water/fish-dispersed fruits present several
morphological characteristics that differentiate them from bird
dispersed fruits. Bird-dispersed taxa have smaller, round, black
fruits that do not fall off the plant when mature, while
water/fish-dispersed taxa have large, blue fruits that fall off when
mature. The seeds of water/fish-dispersed taxa are club shaped and
larger than those of bird dispersed species, which are ovoid to round
or pyramidal. Additionally, the seeds of water/fish-dispersed species
are covered with glandular trichomes, which are absent from
bird-dispersed taxa. Moreover, glandular trichomes are not known from
any other Melastomataceae, including taxa that have been shown to be
ichthyochorus. There are also differences in the phenology of bird
dispersed and water/fish dispersed taxa. Even though ichthyochory has
not been demonstrated to be the main mode of fruit dispersal for any
of these six species of Tococa, many of the characters that
differentiate them from ornithochorous species could be easily
interpreted as adaptations to fish dispersal and not water dispersal.
Key words: fruit dispersal, fruit morphology, ichthyochory, Melastomataceae, seed morphology, Tococa