Alien tree’s sugary SOS exploited by thieving tramp ant: unidirectional benefit in a tritrophic mélange

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Alien tree’s sugary SOS exploited by thieving tramp ant: unidirectional benefit in a tritrophic mélange

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Description

Triadica sebifera (Euphorbiaceae), a centuries old invader of southern ecosystems, was virtually free from natural enemies until the specific, hypermetamorphic moth Caloptilia triadicae (Lepidoptera: Gracillariidae) appeared in 2004. Simultaneously, populations of the destructive tawny crazy ant, Nylanderia fulva (Hymenoptera: Formicidae), spread cospatially across the southeast. To examine potential interactions among these species, we sought answers to these questions: 1) does Caloptilia induce extrafloral nectar production in Triadica; 2) does N. fulva consume nectar, larvae, or both; and 3) does N. fulva provide indirect defense to the tree, or to its attacker? To understand these interactions, and their implications for southern ecosystems, we conducted a series of lab, greenhouse, and field experiments in coastal Texas. In response to herbivory by Caloptilia, potted Triadica saplings strongly induced extrafloral nectar production. Percent leaf damage explained 57% of the variation in cumulative nectar volume (p<.0001), and nectar volume on saplings with >20% of leaves damaged was significantly greater than on controls (p=0.0005). Nylanderia fulva exploited available nectar resources without attacking Caloptilia larvae. On potted saplings, nectar volume was significantly lower when ants were present (p=0.008), while no differences were observed in Caloptilia survivorship (p=0.56). Likewise, no differences in Caloptilia abundance or parasitism rates were observed when ants were excluded from naturally recruited Triadica saplings (p=0.97;p=0.8). Large Caloptilia infestations reduced trunk elongation in Triadica saplings (R2=0.32, p<.0001), but had no effect on leaf production, biomass, or survivorship. Because Triadica saplings supplied N. fulva workers a carbohydrate resource while sustaining heavy damage, and because neither Triadica nor Caloptilia benefited from worker foraging, N. fulva was the only beneficiary in this alien, tritrophic interaction.

Publication Date

4-24-2019

Project Designation

Graduate Research

Primary Advisor

Kathleen A Kargl, Chelse M Prather

Primary Advisor's Department

Biology

Keywords

Stander Symposium poster

Comments

Presenter: Emily Elizabeth Jones, Natalie Christina Martin

Alien tree’s sugary SOS exploited by thieving tramp ant: unidirectional benefit in a tritrophic mélange

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