PARENT SESSION
Oral Session #86: Invasive species: Ants and other invertebrates.
Presiding: J. Morrison
Thursday, August 8. 1:00 PM to 3:45 PM. Greenlee Meeting Room, TCC.

Linking theory and natural history to predict the impact of invasive ants on native mutualisms.

NESS, JOSHUA^*,1, ¹ Institute of Ecology, University of Georgia, Athens, GA

ABSTRACT- Communities invaded by the exotic ants Solenopsis invicta, Linepithema humile, and Pheidole megacephala experience dramatic increases in ant abundance and decreases in arthropod richness and diversity, relative to similar uninvaded sites. These well-studied changes in composition are accompanied by less-appreciated contractions in the ranges of dietary preferences and foraging strategies within the invaded communities. This contraction has implications for provision of benefits in food-for-service mutualisms, an interaction prevalent in most tropical and temperate terrestrial communities. I focus on the effects of these invasions on the participants of three mutualisms in which ants are traditional partners: myrmecochorous plants, honeydew-producing homopterans, and nectaried plants. Models predict that the highly territorial and polydomous nests of all three invasive ant species should lead to diminished seed dispersal distances, and seed dispersal will be directed into, rather than across or from, invaded habitats. Models of ant - Homoptera interactions link the transition from tending to predation with the proximity to nests and the protein vs. carbohydrate deficiencies of these colonies. Elevated abundance and tending of homopterans by L. humile and P. megacephala, but not S. invicta, support these predictions. Lastly, the dietary preferences and physiology of L. humile and P. megacephala appear better-suited for nectar collection than that of S. invicta, although nectaried plants are rarer in the biomes typically invaded by the former two species.

KEY WORDS: myrmecochory, exotics, tending, mutualism