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It's a Jungle Out There ... for Nearly All Ecosystems

Paper Reviewed
Barton, B.T. and Ives, A.R. 2014. Direct and indirect effects of warming on aphids, their predators, and ant mutualists. Ecology 95: 1479-1484.

Authors Barton and Ives (2014) write that "species exist within communities of other interacting species, so that an exogenous force that directly affects one species can indirectly affect all other members of the community." And in the case of climate change, as they continue, "many species may be affected directly and subsequently initiate numerous indirect effects that propagate throughout the community," with the end result that the net effect of climate change on any one species may be a melded function of direct and indirect effects experienced by many co-occurring species.

Further examining this topic, Barton and Ives investigated the direct and indirect effects of climate warming on corn leaf aphids - a pest of corn and other grasses - by performing an experimental manipulation of temperature that also impacted aphid predators and two types of aphid-tending ants. Quoting the two researchers, results indicated that "although warming had a positive direct effect on aphid population growth rate, warming reduced aphid abundance when ants and predators were present." This occurred, as they describe it, "because winter ants, which aggressively defend aphids from predators under control temperatures, were less aggressive toward predators and less abundant when temperatures were increased." In contrast, as they continue, "warming increased the abundance of cornfield ants, but they did not protect aphids from predators with the same vigor as winter ants," such that warming "broke down the ant-aphid mutualism and counterintuitively reduced the abundance of this agricultural pest."

It's truly a jungle out there in the real world of natural ecosystems, both big and small; and one must know how the interacting species of an ecosystem respond to both atmospheric CO2 enrichment and changes in various climatic elements in order to determine the ultimate consequences for the species of primary interest, which in this case were corn and a number of other grasses.

Posted 3 October 2014