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From cryptic herbivore to predator: stable isotopes reveal consistent variability in trophic levels in an ant population
Author(s) -
Roeder Karl A.,
Kaspari Michael
Publication year - 2017
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1002/ecy.1641
Subject(s) - trophic level , ecology , herbivore , ant , predator , biology , population , stable isotope ratio , myrmecophyte , predation , demography , sociology , pollen , physics , quantum mechanics , nectar
Abstract Populations may collectively exhibit a broad diet because individuals have large diet breadths and/or because subpopulations of specialists co‐occur. In social insect populations, the diet of the genetic individual, the colony, may similarly arise because workers are diet generalists or castes of specialists. We used elemental and isotopic methods to explore how the invasive red imported fire ant, Solenopsis invicta , achieves its status as a trophic generalist. In one 0.5‐ha old field, 31 S. invicta colonies ranged from 1°‐consumer to 2°‐predator (δ 15 N's 0.35–7.38‰), a range comparable to that shown in sampled ant communities. Moreover, a colony's trophic rank was stable despite δ 15 N fluctuating 2.98‰ over the year. Colonies that fed at higher trophic levels were not larger, but consumed more C 3 ‐based resources. Individual worker mass, however, did increase with δ 15 N ( r 2 = 0.29, P < 0.001). The ninefold variation in worker mass within a colony generated trophic variance approximately 15% of the population of colonies. Combined, we show how intraspecific trait variation contributes to the trophic breadth of S. invicta , and suggest mechanisms that further explain how their trophic signature varies across space, but remains stable over time.