Research News

    Invasive non-native species may look a lot like their native counterparts, but they don't always act like them and their presence can be incredibly disruptive to normal predator-prey interactions within native food webs. This can have profound ecological consequences when the species most affected is a 'foundation species' that supports biodiversity by creating extensive habitat. Such is the case for the Olympia oyster Ostreola conchaphila, a native species in California estuaries that provides critical nursery habitat for a suite of species including crabs, anemones, and fishes. Even though these remnant reefs of Olympia oysters are normally preyed upon by native predatory snails, they are protected to some extent by the presence of native rock crabs that both consume native snails and force all others to spend more time hiding from crabs rather than eating oysters. Enter invasive snails and crabs that were accidentally introduced from the Atlantic to the Pacific coast and the whole dynamic changes, as revealed by Dr. David Kimbro, a postdoctoral associate at the Florida State University Coastal and Marine Laboratory (FSUCML) and his colleagues.

Kimbro (FSUCML), together with Edwin Grosholz, Adam Baukus, Sarikka Attoe, and Caitlin Coleman-Hulbert (University of California, Davis), and Nicholas Nesbitt and Nicole Travis (Bodega Marine Laboratory), demonstrated that the presence of invasive species, which take the place of the native crabs and snails in the less saline parts of the estuary, completely destroyed the native oyster population. The root cause is the change in interactions between oysters, snails, and crabs. The invasive snail, also known as the Atlantic oyster drill, is unfamiliar with crab predators, and thus fails to avoid them as the native snails do. Moreover, the invasive European green crab, which is smaller than the native crab, cannot effectively control the snail population. This artificial and devastating mis-match between predator and prey then allows high numbers of invasive snails to negatively impact the biological diversity of a pristine California estuary by consuming and eliminating critical oyster habitat.

“You might think that similar looking invasive and native species could be swapped in a system with no real consequence,” says Kimbro. “But what we've shown is that functionally, this is not the case. While the native predator-prey interactions that benefit oyster reefs are intricate and took a long time to develop, the invasive crab and snail do not have the historical exposure that is necessary to recreate these important interactions.”

“I agree,“ says John Stachowicz of University of California, Davis. “Like a long-married couple, native crabs and snails have figured out how to coexist, leaving oyster populations intact. But the lack of experience that introduced crabs and snails have with each other led to destruction of parts of the oyster population. In that respect, the study serves as a warning that predicting consequences of adding new species to our ecosystems will not be easy.”

"In addition, this elegant experiment has true value for management and conservation,” says Hunter Lenihan, marine ecologist at the Bren School, University of California, Santa Barbara. “Plans are being drawn up along the west coast to restore native oysters, and much time and money will be wasted if restoration efforts fail. Kimbro and his colleagues have identified an important restoration bottleneck--invasive species attacks on oysters--that must be dealt with prior to oyster population enhancement and the rebuilding of remnant reefs. Like the eastern oyster, west coast oysters are ecosystem engineers that build reefs that support production of many fish species. More thought must now be given to controlling oyster loss vis a vis predation."

“The study also raises a specter for us in Florida for several reasons,” says Felicia Coleman, Director of the FSU Coastal and Marine Laboratory. “First, we have a remarkably productive native oyster population at risk in the Apalachicola Bay. These oysters are sustainably harvested and provide critically important settlement habitat for a remarkable array of species, so its loss would be devastating. And second, because in Florida's benign climate, exotic species have a fairly easy go of it getting established. One need only follow the trajectories of lionfish, Australian pine, Brazilian pepper, and Burmese python for a gaze through the looking glass.”

As human activities increasingly move species beyond their natural borders, predator-prey mismatches between native and exotic species may lead to further losses of critical habitat that support marine biodiversity and ecosystem function.

For further information contact:

Dr. David Kimbro, FSU Coastal and Marine Laboratory, Phone 850.697.4092, dkimbro@bio.fsu.edu

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