Pollinator specificity, cryptic species and geographical patterns in pollinator responses to sexually deceptive orchids in the genus Chiloglottis: the Chiloglottis gunnii complex
Colin C. Bower A C and Graham R. Brown BA FloraSearch, PO Box 300, Orange, NSW 2800, Australia.
B C/- Museums and Galleries of the Northern Territory, PO Box 4646, Darwin, NT 0801, Australia.
C Corresponding author. Email: colbower@bigpond.net.au
Australian Journal of Botany 57(1) 37-55 https://doi.org/10.1071/BT08164
Submitted: 5 September 2008 Accepted: 19 January 2009 Published: 23 March 2009
Abstract
Australian sexually deceptive orchids are typically highly pollinator specific, each species having a single unique hymenopteran pollinator species. Pollinator specificity in six of the nine described species in the Chiloglottis gunnii Lindl. complex was investigated by using field pollinator-choice tests, with Chiloglottis taxa translocated within and among biogeographical regions. Specific pollinators revealed the existence of five undescribed cryptic taxa in the C. gunnii complex, three within C. pluricallata D.L.Jones and two within C. valida D.L.Jones, in addition to the six described species. Of the 11 Chiloglottis taxa, 10 had a single thynnine-wasp pollinator throughout their sometimes large distributions, whereas one, C. valida, had a second pollinator in parts of its distribution. Eleven pollinators belonged to the genus Neozeleboria and one to Eirone. Pollinator-choice testing showed that cross-attraction of pollinators occurs between three geographically isolated Chiloglottis taxa on the New South Wales (NSW) New England Tableland and taxa in the South Eastern Highlands of NSW and Victoria. The data suggested there is sharing of chemical attractants and supported the recognition of at least five odour types within Chiloglottis, each encompassing one to three orchid taxa and their pollinators. The following two broad generalisations are made: (1) there is no cross-attraction of pollinators among sympatric Chiloglottis species, i.e. sympatric orchid taxa do not share attractant odours; and (2) all Chiloglottis species have different specific pollinators, although they may share attractant odours allopatrically. Some 28 thynnine-wasp species were attracted as minor non-pollinating responders to Chiloglottis taxa; five of these were pollinators of other Chiloglottis species. These wasps were much more taxonomically diverse than the pollinators, belonging to six genera, and suggest that some orchid-odour components are widely shared within the sex pheromones of the Thynninae.
Acknowledgements
David Jones, Rod Peakall, Jim Mant and Florian Schiestl are thanked for their insights, feedback and discussions over the period of this study. Gary Backhouse, Everett Foster, Alan Logan, Jeff Jeanes, Laurie Porteus, John Riley, the late Ron Tunstall and Hans Wapstra helped with details of orchid locations. The manuscript benefited greatly from review by Rod Peakall. Specimens for this study were collected by the senior author under permits issued to the Australian National Herbarium by the NSW National Parks and Wildlife Service, NSW State Forests and Natural Resources and Environment (Vic.). Permit numbers for Tasmania were FA98152 and FA98154 (Parks and Wildlife Service (Tas.)). The Director of the National Herbarium, Canberra, is thanked for allowing the senior author to work as an Associate of the herbarium. Financial assistance from the Australian Orchid Foundation is gratefully acknowledged.
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