A grant has been awarded to Dr. Richard Olmstead and Ms. Susan Grose at the University of Washington to study the evolution of a mammal dispersed fruit in Central America. The study group is the three genera in the Crescentieae, a tribe in the family Bignoniaceae (Trumpet creeper family). The closest relative of these plants is a group of trees in the genus Tabebuia, a tree with dry fruits similar to those of Trumpet creeper. The goals of the research are first to determine the evolutionary relationships of the species under study, and second to analyse the changes that have taken place to produce a fruit palatable to animals from one that is dry and woody. Samples will be collected on an expedition to Mexico and Guatemala. DNA sequence analysis will be used to determine the relationships among the species of Crescentieae and Tabebuia. This work will take place at the University of Washington. The changes that have taken place in the fruit tissues will be studied at the University of Zurich using light and electron microscopy techniques.
This study will enhance our understanding of the relationship between flower and fruit development and the evolution of functionally important traits in a lineage of flowering plants. The Crescentieae are thought to have been eaten by now extinct ice-age mammals, which dispersed the undigested seeds. It is not known which, if any, animals in modern times are eating and dispersing the fruits. Today, Crescentieae are very rare and the species have very localised distributions. They are constantly facing threats of extinction due to deforestation. Understanding how these plants evolved is one step in determining appropriate courses of action for conservation of plant species whose seed dispersers have gone extinct.
