POLLINATION ECOLOGY OF 4 DALECHAMPIA SPECIES (EUPHORBIACEAE) IN NORTHERN NATAL, SOUTH-AFRICA

Citation
Ws. Armbruster et Ke. Steiner, POLLINATION ECOLOGY OF 4 DALECHAMPIA SPECIES (EUPHORBIACEAE) IN NORTHERN NATAL, SOUTH-AFRICA, American journal of botany, 79(3), 1992, pp. 306-313
Citations number
24
Language
INGLESE
art.tipo
Article
Journal title
ISSN journal
0002-9122
Volume
79
Issue
3
Year of publication
1992
Pages
306 - 313
Database
ISI
SICI code
0002-9122(1992)79:3<306:PEO4DS>2.0.ZU;2-Y
Abstract
The pollination ecology of four Dalechampia species was studied in thr ee areas in northern Natal, South Africa. All species were pollinated by resin- and/or pollen-collecting megachilid bees (Hymenoptera: Megac hilidae). The most common of these at all study sites was Heriades sp. (Megachilini), which collected both pollen and resin. This bee was th e primary pollinator of D. galpinii and D. volubilis, and a secondary pollinator of D. aff parvifolia and D. capensis. The primary pollinato rs of these latter two Dalechampia were Pachyanthidium near cucullatum and P. cordatum (Anthididiini), respectively. These are larger bees t hat collected mainly resin. Other visitors varied among Dalechampia sp ecies and among sites. Pairs of Dalechampia species were often found i n sympatry (within 30 m of each other) and shared pollinators to varyi ng extents. "Transfer experiments," in which we placed inflorescences of two Dalechampia species together, reinforced observations of flower discrimination by bees foraging among naturally occurring sympatric p airs. Heriades sp. showed no obvious discrimination between Dalechampi a species, but Pachyanthidium spp. "preferred" the Dalechampia species with the greater resin reward. Occasionally, however, Pachyanthidium would visit less rewarding species. Thus, although sympatric African D alechampia species showed some pollinator partitioning, it was much we aker than found among New World species, and cannot alone explain the general absence of Dalechampia hybrids in northern Natal.