Under the guidance of faculty adviser Dr. Jeffrey Doyle, graduate student Anne Bruneau of Cornell University will study the molecular systematics, morphology, and pollination biology of species in the legume genus Erythrina. Several species are cultivated as street trees in the tropics, used as living fences, or planted as shade trees in coffee and cacao plantations. All Erythrina species have red or orange flowers and are pollinated by either hummingbirds or perching birds (order Passeriformes). Species pollinated by perching birds have wide, gaping flowers that are oriented toward branches or branch tips; species pollinated by hummingbirds have narrow-tubed flowers that face outwards and only birds that hover can obtain nectar, and thereby effect pollination. Hummingbird pollination has been considered more specialized than pollination by perching birds, but this has never been critically tested. Considerable biological and horticultural interest has resulted in the availability of nearly all 112 species in the genus in living collections. Laboratory work will focus on molecular markers of species diversification, obtained from analyses of chloroplast DNA and nuclear ribosomal DNA. Combined molecular and morphological evidence will produce a robust phylogenetic tree for the group. Field work will document the specific pollinators of those remaining species not yet studied. The researchers can then determine the evolutionary relationships between hummingbird- and perching bird-pollinated species and test whether the evolutionary change occurred once or several times among species of this genus.
