The beaver, Castor canadensis, seldom reaches densities anywhere near those achieved by most other rodents. However, its effect on ecosystems can be enormous. By damming streams it creates ponds and wetlands. This can kill trees in the midst of an otherwise continuous stand of climax forest, making room for many aquatic and semiaquatic species. When the beaver move on and the pond fills in, the meadow left behind also represents a new and different habitat type suitable for yet other species. In short, the beaver can dramatically increase the complexity of ecosystems, leaving behind a mosaic of habitat types that supports enormous biodiversity. It is clear from this description that the beaver is __________ in the forest ecosystem.