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Abstract Detail


Karnish, Alex [1], Bronstein, Judith [2].

Exploring Myrmecochory: Does Elaiosome Presence Affect Ant Seed Choice?

The seeds of over 11,000 species of flowering plants have elaiosomes (nutrient-rich fat bodies attached to seeds that act as a food reward) and are dispersed by ants. How the presence or size of an elaiosome determines what seeds ants choose and how that ultimately affects seed dispersal is poorly understood. Previous work on ant seed preference has been contradictory. Given a choice of seed species, ants have been shown to have no preference for elaiosome size, instead preferring to collect species with larger seeds. In contrast, intraspecific seed choice trials have shown that ants prefer seeds with larger elaiosomes regardless of seed size. To test whether elaiosome presence and size impacts ant choice, seed choice experiments were carried out with the harvester ant Pogonomyrmex barbatus and Datura wrightii (Solanaceae). In the field, wild colonies of harvester ants were presented with D. wrightii seeds with and without elaiosomes attached, and seed removal rates were recorded in order to test whether elaiosome presence increased the rate of dispersal. Unexpectedly, contrary to the general understanding of myrmecochory, rather than bringing the seeds to the colony, the ants picked up the seeds and moved them away. This happened regardless of elaiosome presence or absence. Furthermore, seeds with and without elaiosomes were moved away at the same rate (0.2 seeds per minute, p=0.79). These counterintuitive results raise the possibility that the seeds are coated in chemicals, such as oleic acid precursors, that may induce corpse-carrying behavior in the ants. These results also indicate that the interaction between D. wrightii and harvester ants may be a parasitic relationship, in which the ant is bearing the cost of carrying the seed without gaining the benefit of a food reward, rather than the mutualistic interaction that ant-mediated seed dispersal is widely considered to be.

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1 - University Of Arizona, Ecology And Evolutionary Biology, 1041 E. Lowell St., BioSciences West Rm. 305, Tucson, AZ, 85719, United States
2 - Dept Of Ecology & Evol Biology, Bio Sciences W-Univ Of Arizona, Tucson, AZ, 85721, United States

Seed dispersal

Presentation Type: Poster
Session: P, Ecology Posters
Location: Arizona Ballroom/Starr Pass
Date: Monday, July 29th, 2019
Time: 5:30 PM This poster will be presented at 6:15 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PEC030
Abstract ID:910
Candidate for Awards:Ecological Section Best Graduate Student Poster

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