Ana Zangirolame Gonçalves / Unicamp Odontomachus hastatus ant carries prey to its nest: its debris nourishes the Quesnelia arvensis bromeliad, commonly found on Cardoso IslandAna Zangirolame Gonçalves / Unicamp
Some ant species contribute nutrients to their host plants, as in the case of the bromeliad Quesnelia arvensis. Commonly found in the Atlantic Forest of the Brazilian Southeast, it has green leaves with serrated edges and purple flowers. The feces and food remains of ants of the species Odontomachus hastatus, which make their nests among the roots of this plant, and Gnamptogenys moelleri, which shelter among its leaves, provide the plant with much of the nitrogen it needs to produce proteins and grow, according to researchers from the University of Campinas (Unicamp). In a laboratory experiment, biologist Ana Zangirolame Gonçalves quantified the contribution that three ant species make to the bromeliad’s diet. In a greenhouse, she simulated the temperature, moisture and soil conditions in which Quesnelia is found in the restingas, or coastal forests, of Cardoso Island on the southern coast of São Paulo State. She then brought in bromeliad specimens to live for two months with colonies of three ant species–Odontomachus hastatus, Gnamptogenys moelleri and Camponotus crassus. The first two are predators and generally consume small invertebrates. In the tests, they were fed larvae of beetles treated with a diet rich in nitrogen-15, a heaver and rarer variety of that chemical element. Camponotus crassus ants consume sweet nectar and liquids excreted by sap-eating insects. At 1.3 centimeters long, Odontomachus hastatus was the species providing the most nitrogen to the bromeliad—on average, 19% of the total nitrogen consumed by the plant. Much smaller at only 0.5 cm, Gnamptogenys moelleri and Camponotus crassus contributed 16% and 11%, respectively (PLOS One, March 22, 2016). “The findings reinforce the idea that ants can redistribute nutrients among different areas of the forest,” the researchers write. “That role,” says Gonçalves, “is even more important in nutrient-poor environments.”
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