CHEMICAL ECOLOGY ABSTRACTS
Plant-Ant Symbioses in the Understory Melastomataceae of Two Neotropical Rain Forests
García, A.E.1, F. A. Michelangeli1, F.I. Michelangeli2, and E. Rodriguez1
(1Cornell University, 2IVIC; Research conducted at the Yutajé research station and IVIC, Venezuela 1996)
The symbiotic associations between ants and plants are common phenomena in tropical rainforests. By far Melastomataceae is the plant family with the largest amount of species with such associations. Two different study sites were chosen for the present study. In both study sites, all Melastomataceae species bearing ant domatia were identified and collected along with their inhabiting ants. Exclusion experiments were also performed in order to assess the importance of the ants to the biology of the plants. Azteca was the only ant genus present at one of the sites, while at the other Pheidole sp. and Crematogaster sp. were found in association with the plants. The genera of Melastomataceae present were Tococa Aubl. and Myrmidone Mart. The diversity of ant species per host and per locality is discussed. Data of other ant-plant associations in the same area (i.e. Fabaceae, Moraceae, and Boraginaceae) is also considered.
Hummingbird-Plant Interactions in the Venezuelan Amazon
Burke, J.C.1, D. Rosane2, F.I. Michelangeli3, and E. Rodriguez1
(1Cornell University, 2Fundación Terramar, 3IVIC; Research conducted at the Yutajé research station and IVIC, Venezuela 1997)
Hummingbirds and plants often posess a symbiotic relationship. Plants provide life-sustaining nectar for the birds to consume, while hummingbirds provide effective means of pollination for the plants. Coevolution has brought about the morphological changes in both parties that have enabled them to maximize the efficiency of their relationship. The extent of this relationship between 7 species of Venezuelan Amazonian hummingbirds, and the flowering plants Hamelia patens Jacq. (Rubiaceae), Costus spiralis (Jacquin) Roscoe (Costaceae), and Costus guanaiensis Rusby (Costaceae) was investigated. Observations of feeding behavior at floral patches showed that 57% of the H. patens flowers visited by A. versicolor were probed, and 94% of the C. spiralis flowers visited by P. squalidus were probed. SEM analysis of pollen grain samples taken from the beaks of P. squalidus and C. notatus showed that the most abundant pollen on their beaks belonged to the genus Costus. Costus spiralis appeared to have the most rewarding relationship with C. notatus. A. versicolor benefits from its relationship with H. patens, although evidence suggests that it may not be the most efficient pollinator of this plant species.
Mysterious Mushrooms of the Neotropics: The Ecology, Chemistry, Biological Activity, and Ethnomycology of Four Color Variants of Cookeina sulcipes (Berk.) Kuntze (Pezizales, Sarcosyphaceae)
Samuels, K.¹, T. Iturriaga2, F.I. Michelangeli3, and E. Rodriguez4
(¹Emory University, 2Universidad Simon Bolivar, 3IVIC, 4Cornell University; Research conducted at the Yutajé research station and IVIC, Venezuela 1997)
Neotropical rain forests contain one of the world's most diverse assemblages of fungal species. In spite of this variety, the fungi of the tropics and sub-tropics are poorly studied and understood in terms of their chemistry and ecology. Past chemical and antibacterial research on these fungi has focused mainly upon a few species of edible jelly fungi and soil bacteria which have yielded promising anti-cancer and antibacterial compoounds, respectively. This project presents the results of an investigation into the ecology, chemistry, and biological activity (i.e. anti-bacterial, anti-viral, anti-malarial, and cytotoxic properties) of Cookeina sulcipes, as well as a cursory investigation of potential medicinal and/or nutritional use of this species among Piaroa communities in the area surrounding the Yutajé research station. The ecological component of this study investigates the distribution of this abundant (both throughout the tropics and in the Yutajé region) fungal species, with a particular focus on the habitat features that may cause the expression of four different color varieties of C. sulcipes. Preliminary ecological data suggests that there is a correlation between the four diferent color varieties of C. sulcipes and their apothecia size. Data also suggests a correlation between habitat type and the frequency and abundance of the color varieties of this fungal species, with the greatest diversity being found in the white-water terra-firme rain forest. Assay results demonstrate a mild inhibitory effect against Salmonella sp. This species of fungi was not found to be used nutritionally nor medicinally by the Piaroa, although reports exist that this species is eaten by indigenous people in Mexico.
Chemical Ecology of Food Items of Five Frugivorous Amazonian Birds
Schwartz, M.J.1, D. Rosane2, F.I. Michelangeli3, and E. Rodriguez1
(1Cornell University, 2Fundación Terramar, 3IVIC; Research conducted at the Yutajé research station and IVIC, Venezuela 1997)
Birds have long puzzled observers by eating fruits known to contain toxic compounds. Birds may be using a fruit's based on the palatability of anti-bacterial, anti-fungal, or anti-parasitic properties compounds. It is also possible fruits have evolved mild toxicity in order to improve dispersion. Five frugivorous neotropical birds, Ara chloroptera, Pionites melanocephala, Amazonas ochrocephala, Tyrannus savana, and Etaenia cristata, were observed over a six-week period with regards to diet. Items the birds ate were recorded, collected, and identified. Of primary interest was the chemical composition of food items. An extraction of each food item was done with 70% ethanol to determine the presence and type of secondary compounds the birds were ingesting. Fruits were collected from the following genera: Caryocar Linn. (Caryocaraceae), Byrsonima L.C. Rich. ex Kunth (Malpighiaceae), Alchornea Sw. (Euphorbiaceae), Protium Burm f. (Burseraceae), Erythroxylum P. Browne (Erythroxylaceae). Protease inhibitors were found in the pulp of Alchornea sp. and Erythroxylum sp. Caryocar sp. was found to have cytotoxic activity. Further work is being conducted on the potential biomedical uses of these compounds.
