The pesky Argentine ant, which has proliferated throughout the coastal regions of California, invading homes and displacing native species of ants, is also contributing to a sharp decline in the state's population of coastal horned lizards.
In separate papers published this month in the journals Conservation Biology and Ecological Applications, a team of San Diego biologists show that the severe decline in coastal horned lizards in southern California in recent years is intimately tied to the proliferation of Argentine ants, which have displaced many of the larger, native ant species on which the lizards feed.
"While habitat loss is often considered the leading reason for the decline of threatened species, the mechanisms responsible for their decline are often unknown," says Andrew V. Suarez, who conducted the research on both studies while a graduate student at the University of California, San Diego.
"These two studies are relatively unique in that we were able to identify a causal agent contributing to the decline of horned lizards-an invasive ant species. Moreover, this pattern was evident over a really large area ranging from the Mexican border to Los Angeles-a scale at which very few studies have been conducted."
"Our work demonstrates that invasions can have community-wide effects," adds Suarez, now a postdoctoral fellow at the University of California, Berkeley. "Essentially, the impacts of Argentine ants in California starts with the displacement of native ants and then cascades throughout the ecosystem."
The tiny dark-brown and black ants, which are about two millimeters in length, are thought to have entered the United States aboard ships carrying coffee or sugar from Argentina during the 1890s, then expanded throughout California and the southern parts of the United States. In the Southeast and much of the South, their proliferation is limited to some extent by the introduction of fire ants.