PT  - JOURNAL ARTICLE
AU  - Eduardo G P Fox
AU  - Xiaoqing Wu
AU  - Lei Wang
AU  - Li Chen
AU  - Yong-Yue Lu
AU  - Yijuan Xu
TI  - Venom Isosolenopsin A Delivers Rapid Knockdown of Fire Ant Competitors
AID  - 10.1101/454637
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 454637
4099  - http://biorxiv.org/content/early/2018/10/26/454637.short
4100  - http://biorxiv.org/content/early/2018/10/26/454637.full
AB  - Fire ant venoms are composed of insecticidal alkaloids named ‘solenopsins’. Whilst species-specific differences are reported, little attention was given to caste-specific venom adaptations. The venom of fire ants queens has remained poorly studied. Founding queens must succeed in isolation in the field, where venom is bound to play a role against competitor species. The venoms of fire ant queens are strikingly similar across different species, in being mainly composed of the alkaloid isosolenopsin A, regardless of the chemical diversity of the worker caste. From assuming this pattern as the evolutionary result of stabilising trait selection, we hypothesise a shared mechanism explaining the conserved venom composition among the fire ant queens of different species. Here we report that fire ant queen venom and its major compounds are much quicker to neutralise competitor ants than the more diverse venoms of workers. Three representative competitor ant species sympatric with invasive fire ants were selected, exposed on the head to venoms from invasive fire ant workers and queens of two main invasive species, Solenopsis invicta and S. geminata. The venom diversity in the worker caste of these species represent extremes in the chemical diversity of fire ants. Queen venoms delivers quicker knockdown of rival foragers than worker venoms. The effects are traced back to synthetic solenopsins demonstrating solenopsin A analogues are particularly efficient as contact neurotoxins. The observed effects are comparable to nicotine. Overall the venoms of S. invicta seem more lethal than of S. geminata, regardless of knockdown speed. We believe these are fundamental aspects in the chemical ecology of the invasive ants which have been long overlooked, and emphasise on the need for further studies into the venom biology of founding queens.