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Kays et al 2010 - coyote wolf hybridization

1.    Kays, R., A. Curtis, and J.J. Kirchman  2010. Rapid adaptive evolution of northeastern coyotes via hybridization with wolves. Biology Letters, 6 , 89-93 (doi:10.1098/rsbl.2009.0575).
The dramatic expansion of the geographical
range of coyotes over the last 90 years is partly
explained by changes to the landscape and local
extinctions of wolves, but hybridization may
also have facilitated their movement. We present
mtDNA sequence data from 686 eastern coyotes
and measurements of 196 skulls related to their
two-front colonization pattern. We find evidence
for hybridization with Great Lakes wolves only
along the northern front, which is correlated
with larger skull size, increased sexual dimorphism
and a five times faster colonization rate than
the southern front. Northeastern haplotype
diversity is low, suggesting that this population
was founded by very few females moving across
the Saint Lawrence River. This northern front
then spread south and west, eventually coming
in contact with an expanding front of nonhybrid
coyotes in western New York and Pennsylvania.
We suggest that hybridization with wolves
in Canada introduced adaptive variation that
contributed to larger size, which in turn allowed
eastern coyotes to better hunt deer, allowing a
more rapid colonization of new areas than coyotes
without introgressed wolf genes. Thus,
hybridization is a conduit by which genetic variation
from an extirpated species has been
reintroduced into northeastern USA, enabling
northeastern coyotes to occupy a portion of the
niche left vacant by wolves.
Keywords: hybridization; adaptive introgression;
range expansion; genetic variation; morphological
variation