Great numbers of animal and plant species have been introduced, intentionally or not, since the arrival of the Europeans in North America.(80 kb)
Ships travelling between the two worlds sometimes carried little passengersinsects, rodents, spores or seedsthat found favourable living conditions on the new continent and prospered, sometimes to the detriment of native species.
But well before the arrival of humans, similar situations often arose as a result of continental drift. No need for ships to introduce species when distant continents could approach sufficiently close for species to migrate from one to another!(52 kb)
The fauna of the Lower Devonian were very provincial, with each region of the globe having its own characteristic faunal assemblages. Paleontologists have reconstructed these ancient faunal provinces, mainly through the study of invertebrates like brachiopods. The faunal provinces are grouped into a few main realms, such as the Old World Realm and the Eastern Americas Realm. The northern part of Western Europe was included in the Rhenish Province of the Old World Realm, while the Gaspé region and a large part of eastern North America were characterized by fauna of the Appalachian Province of the Eastern Americas Realm.
In Devonian time, changes in the configuration of the continents and oceans promoted faunal exchanges between provinces and realms. As an example, the closure of the Iapetus Ocean during Lower Devonian time facilitated the introduction of Rhenish species along the margin of the Appalachian Province. By the Middle Devonian, many immigrant species from the Old World were highly dispersed in the Eastern Americas Realm. The fauna of the Gaspé Sandstone Group, which span the end of the Lower Devonian to the beginning of Middle Devonian time, document the passage of Rhenish Old World species through the Gaspé Basin during their migration to North America.