Molecular Phylogeography of the American Beaver (Castor Canadensis): Implications for Management and Conservation

Abstract

The American beaver, the largest rodent of North America, is distributed in ponds, lakes, and streams from Alaska to northern Mexico. This semi-aquatic mammal is considered an ecosystem engineer because beavers modify the landscape by cutting trees and by creating dams and ponds that have important effects on the aquatic community structure, providing habitat for aquatic invertebrates, fish, and birds. The American beaver has played an important socioeconomic role in the history of North America due to beavers' fur value, which caused the near extirpation of this mammal at the beginning of the 1900s due to overharvest by early Europeans. Because of the highly specific habitat requirements of beavers, this mammal also suffers the effects of habitat loss in some areas where riparian ecosystems are now scarce. My objectives in this study were to assess how climatic and geological events affected the current distribution of the American beaver in North America, and how the management actions to restore and control beaver populations have affected the genetic structure and conservation of beaver populations. Specifically, I addressed four aspects of the management and conservation genetics of the beaver: 1) a literature review of the management of beavers in the past 100 years; 2) the development of novel microsatellite DNA markers to address the population genetic structure aspects of the study; 3) the use of these microsatellite DNA markers to assess genetic diversity of current populations of beavers and to detect past population bottlenecks; and 4) the use of two mitochondrial DNA genes to resolve the current phylogeography of the American beaver in order to better understand how historical factors have affected the beaver's current distribution and genetic structure in North America. The results from this study provide information of the effects that management actions and climatic events can have on the genetic structure of beavers. This information can be used by wildlife biologists, and land managers, to develop future strategies for management and conservation of the American beaver.