Floral Pigments and Nectar Constituents of Two Bat-Pollinated Plants: Coloration, Nutritional, and Energetic Considerations

Abstract

Anthocyanin pigments and nectar constituents of Cheirostemon platanoides and Kigelia pinnata were analyzed in an effort to define provisionally a syndrome of floral phytochemical characters. Amounts and composition of sugar, protein, amino acid, and phenolic nectar constituents are presented. Genetic homology with related taxa appears to dominate over special adaptation to pollination by bats in determining floral pigments, but some evidence of adaptative change is present in nectar sugar composition. The contribution of nectar constituents to bat nutrition and energetics is discussed. THE EXISTENCE OF SYNDROMES of morphological characters associated with particular classes of pollinators is well documented. Recent evidence suggests that adaptively significant syndromes of phytochemical characters may also be associated with pollinator classes. Such studies have centered around floral pigments (Harborne and Smith 1978) and nectar constituents, especially sugars (Baker 1978). The existence of a morphological syndrome is well established (Faegri and Pijl 1966). This report provisionally defines a corresponding phytochemical bat syndrome. The taxa under investigation are Cheirostemon platanoides Humboldt and Bonpland (Chi ranthodendron pentadactylon Larreat.) (Sterculiaceae) and Kigelia pinnata DC. (Bignoniaceae). Cheirostemon is a monotypic genus native to montane cloud forests of southern Mexico and Guatemala. Kigelia consists of six species and is native to tropical Africa. Both of these taxa have been reported as classical bat-pollinated plants (Vogel 1958, Harris and Baker 1958). MATERIALS AND METHODS Nectar samples were taken from Cheirostemon platanoides plants cultivated at the Botanic Garden of the University of California at Los Angeles and from Kigelia pinnata cultivated at the Los Angeles State and County Arboretum. Samples were frozen and stored at -20 C until analysis. Corolla colors were determined by comparison with Royal Horticultural Society (London) Colour Chart standards. Corolla pigments were extracted into acidified methanol and purified by one-dimensional paper chromatography in BAW (BuOHHOAc-H20, 4:1:5). Pigments were identified by determining of Rf values with four solvents using standard methods (Harborne 1967). Total solids in nectar were determined in the field with a hand refractometer. Nectar sugar composition was determined by paper chromatography with appropriate standards using an ethyl acetatepyridine-water (12:4:5) solvent. Sugars were visualized using a benzidine spray, and subjective judgments of relative amounts were made on the basis of