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Australian Journal of Zoology Australian Journal of Zoology Society
Evolutionary, molecular and comparative zoology
RESEARCH ARTICLE (Open Access)

Ant mediated dispersal of spiny stick insect (Extatosoma tiaratum) eggs and Acacia longifolia seeds is ant-species dependent

Hannah R. Smart https://orcid.org/0000-0002-4558-5845 A B * , Nigel R. Andrew A and James C. O’Hanlon A C
+ Author Affiliations
- Author Affiliations

A Insect Ecology Lab, School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia.

B Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751, Australia.

C School of Science and Technology, University of New England, Armidale, NSW 2351, Australia.

* Correspondence to: H.smart@westernsydney.edu.au

Handling Editor: Paul Cooper

Australian Journal of Zoology 70(4) 105-114 https://doi.org/10.1071/ZO22036
Submitted: 8 September 2022  Accepted: 16 February 2023   Published: 27 April 2023

© 2022 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

Myrmecochory is a widespread mutualism between angiosperm plants and ants, where seed dispersal is facilitated by a nutrient-rich appendage known as the elaiosome. Some species of phasmids (Phasmatodea) have convergently evolved an appendage, the egg capitulum, that is analogous to the elaiosome. Research into ant-mediated dispersal of phasmid eggs is limited. It is unknown whether there are species-specific interactions between ants and phasmid eggs, nor if this variation in ant species behaviour towards eggs parallels behaviour towards seeds. We observed the behaviour of five Australian ant species towards Extatosoma tiaratum eggs and Acacia longifolia seeds. We found that ant species show significant variation in the likelihood of dispersing phasmid eggs and plant seeds. Iridomyrmex purpureus removed the largest quantities of eggs and seeds. Rhytidoponera metallica also removed large amounts of seeds but less eggs. Three species did not remove any eggs but removed small amounts of seeds. We found a species-specific component to dispersal of phasmid eggs and seeds by ants, indicating that this mutualism may depend on partner identity and abundance. Although seeds and eggs have convergently evolved to exploit ant behaviours, they elicit different behaviours in certain ant species, highlighting the complex nature of this interaction.

Keywords: animal vectors, ants, coevolution, dispersal, eggs, mutualism, myrmecochory, phasmids, seeds.


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