|CHAPMAN, J - Oregon State University|
|ITANI, GYO - Kochi University|
|MARKHAM, JOHN - Arch Cape Marine Laboratory|
Submitted to: Biological Invasions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2011
Publication Date: 6/1/2012
Citation: Chapman, J.W., Dumbauld, B.R., Itani, G., Markham, J.C. 2012. An introduced Asian parasite threatens northeastern Pacific estuarine ecosystems. Biological Invasions. 14:1221-1236.
Interpretive Summary: Most species of marine invertebrates are assumed to be native to the area where they are found until contrary evidence appears. This results in significant bias and poor interpretations of community ecology and ecosystem dynamics in cases like the one described here for a bopyrid isopod (Orthione griffenis) which parasitizes mud shrimp, Upogebia pugettensis that inhabit tideflats in estuaries along the Pacific Coast of the U.S. O. griffenis was presumed to be native in North America even though it was not described until 2004 and despite the fact that it is conspicuous and became very abundant potentially causing populations of its host shrimp from California to British Columbia to drastically decline. A closer evaluation revealed that the case for O. griffenis satisfies several criteria for introduced species: 1) earliest discovery was actually in Asia where populations are much more isolated, 2) it was the last discovery among all recorded commensal species for its host, U. pugettensis, 3) it is absent in previously published North American records and early museum collections, 4) the discovery in North America was late relative to its size and relative to the diversity of Asian and North American bopyrid isopods, and 5) its first appearance in North America coincides with a likely transport mechanism – an increase in trade and therefore ballast water traffic between Asia and North America. Orthione griffenis is thus the first recognized introduced species of bopyrid isopod and one of the first recognized introductions to the open coast of the northeast Pacific. Additional overlooked introductions of bopyrid isopod parasites and other species likely exist elsewhere in the world and due to the potential impacts of these introductions, the default assumption of native origin should be abandoned.
Technical Abstract: We test a prevalent assumption in marine ecology that species are native to where they are found until contrary evidence appears. The native assumption significantly biases interpretations of marine community and ecosystem dynamics if it results in oversight of critically important introduced species. The parasitic isopod family Bopyridae includes more than 600 species but, none were previously recognized to be introduced. The bopyrid, Orthione griffenis, was presumed to be native or cryptogenic in North America even though it was not described until 2004 and despite being conspicuous and abundant and dramatically reducing its new native host populations, Upogebia pugettensis, between California and Vancouver, British Columbia. A closer examination revealed that O. griffenis satisfies at least six criteria for introduced species: isolated Asian populations; earliest discovery in Asia; discovery last among North American Upogebia commensal species; absence in previously published North American records and early museum collections; late discovery in North America relative to its size and relative to the diversity of Asian and North American Bopyridae and; first North American appearance plus tolerances and behaviors coinciding with entrainment in ballast water traffic and recent trade patterns between Asia to North America. Thus, Orthione griffenis is the first recognized introduced bopyrid isopod in the world and one of the first recognized open coast introductions to the northeast Pacific. The nonindigenous origin of O. griffenis exposes its particular threat to its new Upogebia host species. Additional overlooked or discounted but ecologically important introduced bopyrids and species of many other taxa are likely to be common in the north Pacific and elsewhere in the world. The default assumption of native origin thus biases interpretations of marine ecosystems and should be abandoned.