Closely related species sometimes hybridize in the wild where ranges and habitat niches intersect. For abundant species, this hybridization may have little effect. The genetic reservoir in the primary populations tends to overwhelm the crosses. For species that are rare or uncommon, however, hybridization with a more common species can pose a threat. Hybridization can be a particularly severe threat when it involves an invasive species, as is the case with the rusty crayfish, which has invaded the upper Great Lakes region and is hybridizing with native crayfish (Perry et al. 2001).

In Michigan, Black Ducks show little genetic differentiation from mallards, in part due to frequent hybridization (Ankney et al. 1986). Black Duck range and habitat selection is more restricted and the population is far smaller than that of mallards in the same range. Although the relationship between mallards and Black Ducks is still debated, hybridization is recognized as a threat to the latter species (Ankney et al. 1987). Hybridization between Golden-winged and Blue-winged warblers, both SGCN, has been made possible by human-caused changes to their environments (Levin 2002).

The smallmouth salamander reaches the northern edge of its range in southeastern Michigan. These salamanders are rare in Michigan, but can be locally abundant. Smallmouth salamanders hybridize with others in the Ambystoma genus (Harding 1997); in Michigan, this hybridization usually occurs with blue-spotted salamanders. Low abundance of this species in Michigan makes it susceptible to loss by hybridization.

Conservation Needs to Address Hybridization Issues:

Land, Water & Species Management

• Identify actions that can protect strong pure-strain population centers of species that readily hybridize
  
  
• Develop management strategies to prevent hybridization of native species with newly invading species

Research, Surveys & Monitoring

• Continue research into effects and potential threats of hybridization
  
  
• Identify strong pure-strain population centers of species that readily hybridize
  
  
• Conduct research to identify primary issues that make populations vulnerable to loss by hybridization
  
  
• Monitor newly invading species and identify potential hybridization threats to native species