Pollination by multiple species of nectar foraging Hymenoptera in Prasophyllum innubum, a critically endangered orchid of the Australian Alps

Tobias Hayashi; Bronwyn M. Ayre; Björn Bohman; Graham R. Brown; Noushka Reiter; Ryan D. Phillips

doi:10.1071/BT23110

RESEARCH ARTICLE (Open Access)

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Pollination by multiple species of nectar foraging Hymenoptera in Prasophyllum innubum, a critically endangered orchid of the Australian Alps

Tobias Hayashi ^A ^B ^C ^# , Bronwyn M. Ayre

^A ^B ^# , Björn Bohman ^D ^E , Graham R. Brown ^F ^G ^H , Noushka Reiter

^A ^B ^C and Ryan D. Phillips

^A ^B ^*

+ Author Affiliations

- Author Affiliations

^A Department of Environment and Genetics and the Research Centre for Future Landscapes, La Trobe University, Melbourne, Vic, Australia.

^B Royal Botanic Gardens Victoria, Science Division, Corner of Ballarto Road and Botanic Drive, Cranbourne, Vic 3977, Australia.

^C Ecology and Evolution, Research School of Biology, The Australian National University, Canberra, ACT 2600, Australia.

^D School of Molecular Sciences, The University of Western Australia, Crawley, WA, Australia.

^E Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Lomma, Sweden.

^F Natural Sciences, Museum and Art Gallery of the Northern Territory, GPO Box 4646, Darwin, NT 0801, Australia.

^G CSIRO Land and Water, Private Mail Bag 44, Winnellie, NT 0822, Australia.

^H Research Institute for Environment and Livelihoods, Charles Darwin University, Darwin, NT 0909, Australia.

^* Correspondence to: R.Phillips@latrobe.edu.au

Handling Editor: James Camac

Australian Journal of Botany 72, BT23110 https://doi.org/10.1071/BT23110

Submitted: 21 December 2023 Accepted: 11 June 2024 Published: 8 July 2024

© 2024 The Author(s) (or their employer(s)). Published by CSIRO Publishing. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

Context

Australia has numerous threatened species of terrestrial orchid, with a particularly high incidence of rarity in the genus Prasophyllum R.Br. Although there has been research on mycorrhizal associations and propagation, little is known about the reproductive ecology of threatened Prasophyllum. Understanding which animals are responsible for pollination and the impact of herbivores on reproduction may inform conservation actions.

Aims

For the nationally Critically Endangered Prasophyllum innubum, we aimed to determine the pollinator species, test for self-pollination, quantify levels of reproductive success and herbivory, and identify herbivores.

Methods

Pollinator observations were undertaken at wild populations of P. innubum, whereas an experiment testing for self-pollination was undertaken in shadehouse conditions. We quantified reproductive success and herbivory at two populations and attempted to identify herbivores using game cameras.

Key results

Pollination occurred via three species of bee and a sphecid wasp, all of which attempted feeding on floral nectar. Fruit set averaged 72–84% at wild sites, whereas only 6% of flowers set fruit via self-pollination when insects were excluded. Just 4% of inflorescences were completely consumed by herbivores, and no herbivory was captured on camera.

Conclusions

P. innubum has a generalist rewarding pollination system that confers high levels of reproductive success, with herbivory having little impact on reproduction.

Implications

Pollinator availability is unlikely to restrict conservation translocation site selection of P. innubum because of a generalist pollination system. If herbivores are a threat for this species, it is likely to be through alteration of habitat rather than direct grazing.

Keywords: Australia, conservation, Halictidae, Hymenoptera, Lasioglossum, orchid, pollination, Prasophyllum, reproduction, Specidae.

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