Pollination of Diuris maculata (Orchidaceae) by male Trichocolletes venustus bees
James O. Indsto A B F , Peter H. Weston A , 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, La Trobe University, Bundoora, Vic. 3086, Australia.
E Earth and Life Sciences, Macquarie University, North Ryde, NSW 2113, Australia.
F Corresponding author. Email: James.Indsto@bigpond.com
Australian Journal of Botany 54(7) 669-679 https://doi.org/10.1071/BT05146
Submitted: 29 August 2005 Accepted: 18 May 2006 Published: 19 October 2006
Abstract
In a previous study, the Australian terrestrial orchid Diuris maculata sensu lato, from a site near Melbourne in Victoria, was suggested to be a floral mimic of several sympatric legume species. The widespread distribution of this orchid species (or species complex) suggests that there may be a number of different model and pollinator species throughout this range, and that additional studies are necessary to characterise its pollination adequately. In this study, the pollination of D. maculata in the Sydney region, mainly at Scheyville National Park, was compared with the results previously obtained in Victoria. At Scheyville National Park, Trichocolletes venustus was the only native bee species found in significant numbers, and the flowers it visited were almost exclusively the legumes Hardenbergia violacea and Daviesia ulicifolia ssp. ulicifolia. Fifty per cent (14 of 28) of captured male bees carried D. maculata orchid pollinaria, or remnants, which were identified by AFLP fingerprinting. Female bees, which appeared about 10–14 days after males, were not observed visiting the orchid or carrying orchid pollinaria. We confirmed that D. maculata flowers lack nectar, and noted that the pea-like flowers possess an UV false nectar guide comparable to the true UV nectar guide of the legume flowers. Colorimetric analysis showed the colour separation between D. ulicifolia ssp. ulicifolia and the orchid is small enough to be likely to produce foraging errors, consistent with mimicry. We conclude that guild mimicry of a diversity of ‘egg and bacon’ legumes best explains the pollination of D. maculata s.l., rather than precise mimicry of any one pea species. Preliminary observations suggest that pea-flower mimicry may range from being highly precise in some species, through to being much more generalised, but still retaining elements of mimicry. The novel finding of comparable UV patterns in Diuris species and putative pea models applies to most species in the genus and we found that the rare D. aequalis shows remarkable similarity in colour, shape and UV patterns to the sympatric legume Gompholobium huegelii, and is likely to be a mimic of this species.
Acknowledgments
This article is part completion of a Master of Science degree at the University of Wollongong by J. I. 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 Andrew Perkins for advice on orchid localities and timing of flowering. We also thank Col Bower for his critical reading of the manuscript and numerous helpful suggestions. This is publication Number 2 from the Ecology and Genetics Group at the University of Wollongong.
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