Revista Chilena de Historia Natural 80 (3): 309-325, 2007
RESEARCH ARTICLE
Identifying the mechanisms underlying the invasion of Castor canadensis
(Rodentia) into Tierra del Fuego archipelago, Chile
Castor canadensis is considered an archetypical ecosystem engineer,
which modifies the state of biotic and abiotic factors through non-trophic interactions. This species was introduced by the Argentinean
government into Tierra del Fuego island in 1946, and subsequently colonized autonomously the neighboring islands of Navarino,
Dawson and Hoste. Currently this invader occupies contrasting ecosystems such as the Magellan subpolar beech forest and
Patagonian scrub and steppe. This ability to colonize contrasting habitats suggests that beaver expansion will be limited mainly by
hydrological resources, threatening to colonize the complete extent of temperate beech forests on the mainland (from 35 to 55º S). The
present review proposes three hypotheses regarding the underlying mechanisms to this successful invasion: natural enemy escape,
resource opportunities, and self-facilitation through non-trophic interactions. Current knowledge regarding beaver colonization and
foraging behavior (e.g., habitat selection independently of forest availability, irruptive population growth, and apparent selective
exploitation of Nothofagus pumilio, dominant species in the Magellan forest) suggests that enemy escape and resource
opportunity are the main mechanisms underlying this invasion. The observation of higher densities of active colonies, where the extent
of beaver habitat modification is larger, suggests that self-facilitation may be relevant to the success of this invasion. Current
information does not allow testing these hypotheses, but it provides a framework to develop future investigations regarding this invasion
in Tierra del Fuego.
Key words:
Castor
canadensis, Patagonia, enemy escape, resource opportunity, non-trophic interactions
