Biology of invasive Argentine ants Andrew Suarez, University of Illinois

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1 Biology of invasive Argentine ants Andrew Suarez, University of Illinois Characteristics that may make Argentine ants proficient colonists General nesting and dietary requirements allows close association with humans and disturbance Have many queens Colony reproduction occurs by budding Unicolonial colony structure

2 Rice Canyon Total native ant diversity: 26 species

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4 Mechanisms responsible for invasion success in Argentine ants: Escape from natural enemies, predators and parasites. Pre-adapted to disturbed environments. Different competitive environment - competitive release. Increased competitive ability

5 The fire ant and the Argentine ant are native to the same part of South America! native range of L. humile from Wild 2004 native range of S. invicta from Mescher 2003

6 Insight from comparisons between native and introduced populations: Community competitive hierarchies Trophic ecology: Carbon and nitrogen isotope analyses Variation in colony structure / colony size

7 Stable isotopes Nitrogen Natural abundance: 14 N ~99.63% 15 N ~0.37%

8 Stable Isotope Analysis δ = [(R sample / R standard ) 1] x 1000 R = heavy/light N: 15 N/ 14 N Nitrogen ~ 2-3 enrichment with each trophic level - Higher δ 15 N values indicate higher trophic level TL1 TL2 TL3 TL4 TL5

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10 Forelius cf. breviscapus (1) Pheidole triconstricta (1) Brachymyrmex sp. B (1) Forelius brasiliensis (6) Pheidole cf. obscurithorax (2) Odontomachus haematodus (3) Pogonomyrmex sp. A (3) Dorymyrmex sp. A (2) Solenopsis (Diplorhoptrum) sp. A (2) Azteca sp. A (1) Brachymyrmex sp. A (5) Dorymyrmex thoracicus (5) Pheidole sp. A (Flavens group) (1) Paratrechina sp. A (6) Solenopsis (Diplorhoptrum) sp. B (1) Linepithema humile (14) Camponotus blandus (2) Crematogaster rochai (3) Camponotus cf. mus (2) Pseudomyrmex urbanus (1) Pseudomyrmex rufiventris (3) Pseudomyrmex denticollis (2) Crematogaster cf. quadriformis (2) Solenopsis (Diplorhoptrum) sp. C (1) Acromyrmex heyerii (5) Cephalotes maculatus (1) Camponotus rufipes (2) Camponotus punctulatus/germani (8) Camponotus sp. A (2) Cephalotes jheringi (3) Cyphomyrmex nr. major (1) Cephalotes depressus (3) Acromyrmex lundi (6) Leptothorax sp. A (1) Pseudomyrmex acanthibus (1) Pseudomyrmex gracilis (1) Predators (31) Leaf herbivores (37) Phloem feeders (6) Plants (21) Native population δ 15 N

11 Wasmannia auropunctata (2) Linepithema humile (6) Pheidole laevinota (3) Solenopsis richteri (6) Ectatomma edentatum (3) Crematogaster sp. B (2) Pogonomyrmex naegelli (3) Crematogaster sp. A (2) Dorymyrmex sp. A (1) Pseudomyrmex PSW-19 (3) Acromyrmex heyerii (4) Solenopsis (Diplorhoptrum) sp. A (2) Pseudomyrmex phyllophilus (5) Acromyrmex lundi (4) Pheidole aberrans (1) Camponotus sp. A (2) Solenopsis (Diplorhoptrum) sp. B (1) Pheidole obscurifrons (1) Pogonomyrmex coarctatus (3) Cephalotes jheringi (1) Predators (21) Leaf Herbivores (11) Phloem feeders (10) Plants (15) Native population δ 15 N

12 Pheidole vistana (5) Neivamyrmex cf. leonardi (1) Forelius mccooki (10) Solenopsis xyloni (8) Linepithema humile (8) Messor andrei (8) Crematogaster californica (9) Pseudomyrmex apache (2) Predators (5) Herbivores (14) Plants (6) Introduced population δ 15 N

13 Neivamyrmex opacithorax (1) Pheidole vistana (7) Formica moki (1) Pogonomyrmex subnitidus (10) Crematogaster californica (4) Dorymyrmex insanus (8) Linepithema humile (8) Solenopsis xyloni (5) Prenolepis imparis (3) Solenopsis molesta (2) Camponotus dumetorum (12) Myrmecocyctus testaceus (1) Predators (6) Herbivores (6) Plants (6) Introduced population δ 15 N

14 Relative Trophic Position OT HE OC SW EL TO native range (Argentina) introduced range (California) Tillberg et al. 2007

15 Rice Canyon

16 Rice Canyon Change in Argentine ant δ15n during invasion: Invasion front: DF = 4, H = 4, P = 0.41 Behind invasion front: DF = 5, H = 13.28, P = 0.021

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19 Recruitment to Carbohydrate Baits by Solenopsis invicta Baits on the Ground Baits at 1 m on Trees Proportion of Baits with Fire Ants Villa Ocam po, Site 1 Villa Ocam po, Site 2 College Station, TX Overton, TX Auburn, AL Proportion of Vials with Fire Ants Villa Ocam po, Site 1 Villa Ocam po, Site 2 College Station, TX Overton, TX Auburn, AL Argentina USA Argentina USA Wilder, Eubanks, Suarez, Holway, unpub. data

20 Menke et al. in press

21 Pogonomyrmex badius mixed diet: insects & seeds

22 Elemental Composition of Castes 9 8 AH CC 7 Carbon:Nitrogen Minor Major Queen AH Minor Major Queen CC Male

23 Trophic Ecology of Castes Callibration Samples Nitrogen Isotope Ratio *** AH CC Predator Herbivore Seeds Minor Major Queen AH Minor Major Queen CC Male Smith and Suarez (2010)