Brunet, A.K., R.M Zink, K.M. Kramer, R.C. Blackwell-Rago, S.L. Farrell, T.V. Line, and E.C. Birney. 2001. Distribution, habitat use, and identification of masked shrews, Sorex cinereus and Sorex haydeni, in Minnesota. Final report submitted to the Minnesota Department of Natural Resources. 13 pp.
Several studies support specific status for the prairie form of Sorex cinereus, designated as Sorex haydeni. Evidence for introgression between these species has been found in Alberta despite significant sequence differences (>15%) in mitochondrial DNA. We identified to species 94 masked shrews using mtDNA and morphological criteria to assess the distribution of these two species in Minnesota and to examine the extent of introgression in zones of sympatry. Only four specimens scored genetically and morphologically as S. haydeni, indicating its restricted distribution. Four specimens had incongruent genetic and morphological identifications, suggesting introgression between the two species.