Generalised pollination of Diuris alba (Orchidaceae) by small bees and wasps
James O. Indsto A B F , Peter H. Weston A F , Mark A. Clements C , Adrian G. Dyer D , Michael Batley E and Robert J. Whelan BA National Herbarium of New South Wales, Royal Botanic Gardens and Domain Trust, NSW 2000, Australia.
B Institute for Conservation Biology, University of Wollongong, NSW 2522, Australia.
C Centre for Plant Biodiversity Research, National Botanic Gardens, Canberra, ACT 2600, Australia.
D Department of Clinical Vision Sciences, Faculty of Health Sciences, LaTrobe University, Bundoora, Vic. 3086, Australia.
E Earth and Life Sciences, Macquarie University, North Ryde, NSW 2113, Australia.
F Corresponding authors. Email: James.Indsto@optusnet.com.au or peter.weston@rbgsyd.nsw.gov.au
Australian Journal of Botany 55(6) 628-634 https://doi.org/10.1071/BT06207
Submitted: 16 October 2006 Accepted: 26 March 2007 Published: 27 September 2007
Abstract
Most Diuris species possess flowers of pea-like form and colour, and occur in association with flowering peas of the tribe Mirbeliae. Previous studies of the pollination of Diuris maculata sensu lato have found evidence for guild mimicry of pea flowers. The flowers of Diuris alba are also pea-like in form but not in colour, and this species is frequently found in habitats where peas are uncommon or absent. We investigated the pollination of Diuris alba, which we expected may have a distinct pollination system at Lake Munmorah, New South Wales. Many Diuris species lack floral rewards, but D. alba produced a small amount of nectar. Flower visitors, and hence putative pollinators, were mainly female Exoneura bees, but also the wasps Eurys pulcher and a Paralastor species. Reproductive success of D. alba, both in woodland containing abundant Dillwynia retorta and in heathland where this pea was absent, was higher than in the previously studied D. maculata s.l. We suggest that the pollination of D. alba is more generalised than that found in the legume guild mimic D. maculata s.l. Although its flowers may display structural similarity to pea flowers, other characteristics suggest that its pollination system has diverged from a presumed pea-mimicry ancestral condition.
Acknowledgements
This article is part completion of a Master of Science degree by JI. We acknowledge the financial support of the Joyce Vickery Scientific Research Fund, the Australian Orchid Foundation and the Hermon Slade Orchid Fund. We thank the NSW National Parks and Wildlife Service for permits to complete the study and John Riley and Boris Branwhite for advice on orchid localities and timing of flowering. We thank the Physics Department at Monash University for use of their spectrophotometer.
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