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

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. Some phasmids have evolved a strategy that utilises ants to disperse eggs. We investigated whether there are species-specific interactions between ants and eggs and if variation in ant behaviour towards eggs parallels that towards seeds. We found that some species show different behavioural responses to eggs and seeds, suggesting a species-specific component to dispersal. Photograph by Hannah Smart. [ABSTRACT FROM AUTHOR]