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True omnivores are animals which feed on both plant and prey sources, allowing them to effect multiple trophic levels within a food web. Ants are well-known omnivores and many participate in honeydew mutualisms with aphids. The western thatching ant, Formica obscuripe, tends the mutualist aphid Aphis lupine and will directly feed on the stems and inflorescences of the aphids’ host plant, lupine, Lupinus spp. To understand the net effect of the thatching ant on lupine I looked at the ants effects on herbivores, aphids, and predators on the lupine, along with direct ant damage to the plant. I used a 2X2 factorial experiment crossing the observational factor, lupine near or far from ants with the manipulative factor, the presence or absence of aphids. Close proximity to thatching ants was associated with a significantly greater abundance of aphids, all ant species combined, the number of lupine flowers with chewing damage at the beginning of the experiment, the abundance of both other phloem feeding and chewing herbivores, and the average number of mature seeds and seed weight per infloresence. Ants were also associated with significantly decreased aphid predator abundance on lupine. A structural equation model revealed that the net effect of thatching ants on lupine is positive, with the number of mature lupine seeds increasing in the presence of ants, and with the ants direct effect on the lupine having the greatest overall effect on the plant. Possible explanations for this outcome include differences in microclimate between observation locations. Further studies should be conducted to determine if microhabitat or other unknown factors are responsible for the positive correlation between proximity to thatching ants and lupine fitness. Key Word The western thatching ant, Formica obscuripes, structural equation model, ant omnivory, Lupinus spp., aphid manipulation, Aphis lupine, honeydew mutualism
Knowledge graph centered on What's for lunch: deciphering ant omnivory on lupi with 14 nodes and 55 connections. Top connected: Ligusticum porteri, Lupinus, reproductive success, mutualistic relationships, Formica obscuripes.
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