Floral Biology of Markea neurantha Hemsley (Solanaceae), a Bat-pollinated Epiphyte

Abstract

The floral biology of Markea neurantha Hemsley, a bat-pollinated epiphytic shrub, was studied in the eastern lowlands of Costa Rica. Individual plants may flower for months but only a few buds open each night. Anthesis occurs at dusk and copious amounts of a dilute, hexose-dominated nectar are secreted. Nectar production is highest in the early evening and is effectively terminated by midnight. The open corollas begin to abscise by 2200 hr and do not remain on the plant until dawn. Temporal patterns of nectar and pollen availability and extrinsic bat activity correspond closely. Details of the floral phenology and morphology of M. neuran.tha; are consistent with Baker's (1973) hypothesis that this plant is adapted for pollination by traplining bats. INTRODUCTION Bats which feed largely or exclusively on flowers comprise a unique and interesting element of tropical vertebrate communities. Although information on the ecology of nectivorous bats is slowly accumulating (cf. Baker, 1973; Heithaus et at., 1974, 1975), much remains to be learned. In this context, it seems important to understand the nature of the vegetative resources exploited by these chiropterans. This paper reports information on the floral biology of Markea neurantha Hemsley (Solanaceae), a Central American bat-pollinated shrub, discusses these data in terms of bat-plant coevolution, and indicates some aspects of bat-flower relationships deserving future study. MATERIALS AND METHODS We studied Markea in the field from 2-4 August 1977 at Finca La Selva, a field station of the Organization for Tropical Studies, in Heredia Province, Costa Rica. Finca La Selva, located on the Rio Puerto Viejo, occupies a zone of transition between the Tropical Wet and Premontane Wet Forests of Holdridge (1967). Nectar was collected with 10 microliter (,ul) glass microcapillary tubes introduced into the corolla. Sugar concentration of fresh nectar was measured in sucrose equivalents (% dissolved solids) with a Bausch and Lomb pocket refractometer. Nectar was spotted on filter paper and pollen was collected in a 10% sucrose solution for later analyses. Separation of the amino acid constituents of nectar and pollen was effected in the laboratory by polyamide Thin Layer Chromatography. Separated amino acid spots were removed from the plate, and the fluorescent derivatives eluted with 0.3 mls of chloroform:methanol:acetic acid (7:2:2 v/v/v). Fluorescence was then measured using a microcuvette attachment on the High Sensitivity sample holder of a Turner Filter Fluorometer, Model III (I. Baker, pers. comm.). Results are expressed as proportions of total fluorescence. Most of the field data were derived from inflorescences enclosed by standard Japanese mist nets, but otherwise exposed. Four inflorescences were also enclosed in paper bags in situ and sampled at intervals during, the night. Pollen was removed 1 Present address: Division of Mammals, Museum of Zoology, University of Michigan, Ann Arbor 48109. 2 Present address: Department of Botany, Duke University, Durham, North Carolina 27706. 3 Present address: Department of Ecology and Evolutionary Biology, University of Arizona; Tucson 85721. 4 Present address: Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts 02138. 5 Present address: Department of Ecology and Evolution, State University of New York at Stony Brook, Stony Brook 11794.