Pre-colonial and colonial invasions: crytogenic species
We often focus on the invasions that have occurred in our lifetime as the most compelling and important ones, in part because we can judge their immediate economic and social impact on our lives and on our use of natural resources. While we have some insight into invasions of the nineteenth century ( Marine bioinvasions of New England), European ships have regularly visited the New England coast since the sixteenth century, their hulls laden with fouling organisms; boring organisms such as shipworms (clams) and gribbles (isopod crustaceans), and beach-dwelling organisms in their rock and sand ballast. We know little about European species that arrived early on our shores and are now erroneously considered native (or "amphiatlantic" in biogeographer's parlance). If there was one successful invasion every five years between 1600 and 1800---a probable underestimate given how richly laden with life these early ships, acting as floating "biological islands," were---then at least 40 species, some of which may now be common "engineers" of New England marine communities, are unrecognized early invaders. In classical biogeography and ecology, species whose histories we do not know are considered as native. However, we now classify more and more species as cryptogenic, species that are neither clearly native nor introduced. Older invasions are of no less interest than newer invasions in terms of our understanding of the ecology of marine communities and environmental change. Because a species was introduced 100 or 200 or 300 years ago, it is no less an invader, nor is it necessarily integrated into the natural community that was here, a process that may take thousands of years or more.
---James Carlton