Australian Journal of Botany Australian Journal of Botany Society
Southern hemisphere botanical ecosystems
RESEARCH ARTICLE

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 B

A 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 http://dx.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.


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