2010 NORTHEASTERN NATURALIST 17(2):205–210
A Perspective on the Genetic Composition of Eastern Coyotes
Steven M. Chambers*
Abstract - Way et al. (2010) define a “coywolf” population in the northeastern
United States and eastern Canada that originated through hybridization between
Canis lycaon (Eastern Wolf) and Canis latrans (Coyote), but they maintain that it
is now genetically uniform and only minimally influenced by either parental species.
An alternative interpretation of available data is that this northeastern Coyote
population is genetically diverse, substantially more Coyote than Eastern Wolf in its
genetic composition, and part of a larger population of Coyotes that interbreeds with
a hybrid Coyote/Eastern Wolf population in southern Ontario and western Coyotes
in western New York and Pennsylvania.
Introduction
A series of recent papers have provided extensive information on the genetic
characteristics of populations of the genus Canis in eastern Canada and
the northeastern United States (Wilson et al. 2000, 2003, 2009; Grewal et al.
2004; Koblmüller et al. 2009; Kyle et al. 2006; Leonard and Wayne 2007;
Rutledge et al., in press; Wheeldon and White 2009). A primary interest of
these studies has been the interbreeding between Canis latrans Say (Coyote)
and Canis lycaon Schreber (Eastern Wolf ; also has been referred to as
Great Lakes wolf), which is considered by some authors (e.g., Nowak 2009)
to be a subspecies of Canis lupus L. (Gray Wolf), or the result of previous
hybridization between Coyotes and Gray Wolves (Lehman et al. 1991). Way
et al. (2010) have now extended this series of investigations to include a
population of Coyotes in eastern Massachusetts. Way et al. (2010) conclude
that, although the Coyote population of the northeastern United States is of
hybrid (Eastern Wolf x Coyote) origin, it is relatively uniform in its genetic
composition, and is morphologically and genetically distinct from other
Canis, including Eastern Wolf. They define the range of this population as
“east of longitude 80º including New England, New York, New Jersey, Pennsylvania,
Ontario, and Quebec,” and propose the vernacular name “coywolf”
to reflect its hybrid origin and distinctiveness. A close examination of the
genetic data and analysis of Way et al. (2010) and of another recent study
that included northeastern Coyotes (Kays et al. 2010a) suggests an alternative
genetic characterization of northeastern Coyotes.
Nuclear Microsatellite DNA Variation
The case of Way et al. (2010) for the distinctiveness of the northeastern
Coyote population is based largely on two different analyses of nuclear
*Division of Ecological Services, US Fish and Wildlife Service, PO Box 1306, Albuquerque,
NM 87103; steve_chambers@fws.gov.
206 Northeastern Naturalist Vol. 17, No. 2
microsatellite DNA variation: STRUCTURE and factorial correspondence
analysis. STRUCTURE (Pritchard et al. 2000) is a model-based method for
analyzing multi-locus genetic data to identify population clusters or cryptic
population structure. The method is very widely applied to microsatellite
DNA data. Pritchard et al. (2000) warn that clusters identified by their
method may not correspond to “real”, biological populations if individuals
have mixed ancestry, or where populations are continuous and exhibit isolation
by distance. Schwartz and McKelvey (2009) have further explored the
problem of sampling continuous distributions and confirmed that clusters
identified by STRUCTURE can sometimes be artifacts of sampling and have
no biological meaning. Unfortunately, both hybridization and continuous
distribution are evident in the Coyote population of eastern North America,
so caution is required before accepting the discreteness of units identified by
STRUCTURE.
A close examination of the results of the STRUCTURE analysis (Fig. 2
in Way et al. 2010) reveals that rather than isolation of northeastern Coyotes
from Eastern Wolves from southern Ontario, they are genetically connected
across the Frontenac Axis where individuals with both Coyote and Eastern
Wolf genetic markers are common. This pattern was detected and described
in earlier studies (Grewal et al. 2004, Wilson et al. 2009). The abrupt-appearing
discontinuity between northeastern Coyotes and “western” Coyotes
(from Ohio, North Carolina, and Texas) in Way et al. (2010) can be attributed
to sampling pattern: the Coyotes are represented by widely spaced samples
from a continuous population. These are the conditions that Pritchard et al.
(2000) and Schwartz and McKelvey (2009) warn can lead to recognition of
artifacts of sampling as biological clusters.
The factorial correspondence analysis (Fig. 3 in Way et al. 2010) portrays
variation among individuals at the 8 microsatellite DNA loci. Visual
examination of pattern in these scatter plots can be challenging, but drawing
polygons that enclose the area occupied by a particular symbol can be helpful
in comparing groupings of the data. In this case, the area occupied by
symbols for northeastern Coyotes overlaps with and is transitional between
other Coyotes (from Ohio, North Carolina, and Texas) and the Algonquin
Provincial Park, ON, population of Eastern Wolves. About 1/3 of the polygon
occupied by northeastern Coyotes overlaps with Eastern Wolves, and
1/3 overlaps with the polygon occupied by the pooled sample of Coyotes
from Ohio, North Carolina, and Texas.The microsatellite data therefore
favor an interpretation of the northeastern Coyote population as a genetic
bridge between Coyotes and the Eastern Wolves, rather than as a population
that is genetically distinct from and “minimally influenced” by Coyotes and
Eastern Wolves.
Mitochondrial DNA Variation
Another recent study of northeastern Coyotes presented information
from control region sequences of mitochondrial DNA (mtDNA) (Kays et
2010 S.M. Chambers 207
al. 2010a). They found that about 1/3 of the Coyotes in the northeast (New
England, southern Quebec, New Jersey, and eastern portions of Pennsylvania
and New York) had Eastern Wolf haplotypes. This result is consistent
with the finding of Way et al. (2010) that 21 of the 67 (31%) Massachusetts
Coyotes had the C1 haplotype, which is considered a marker for Eastern
Wolves (Wilson et al. 2000). Fewer Eastern Wolf haplotypes were found in
Coyotes from western portions of Pennsylvania and New York, and Coyotes
from Ohio had only Coyote haplotypes. Kays et al. (2010a) interpret these
results as indicating two routes for Coyotes in a recent invasion of the eastern
United States: (1) Coyotes invading north of the Great Lakes encountered
Eastern Wolves and incorporated Eastern Wolf mtDNA haplotypes
into their population as a result of hybridization, and (2) Coyotes invading
south of the Great Lakes show no Eastern Wolf influence because Eastern
Wolves had been extirpated from that pathway prior to the time of the Coyote
immigration. While agreeing with Kays et al. (2010a) about the contribution
of Eastern Wolf introgression to northeastern Coyotes, Wheeldon et al.
(2010) propose that the pathway that led to contact with Eastern Wolves in
southern Ontario was through the lower peninsula of Michigan rather than
from Minnesota and north of the Great Lakes. Kays et al. (2010b) responded
with new mtDNA data that indicate the presence of northeastern Coyote
mtDNA haplotypes in Coyotes from Minnesota and the upper peninsula
of Michigan. Kays et al. (2010b) provide additional support for a northern
route from museum records of pre-1940 Coyote presence in Minnesota, the
upper peninsula of Michigan, and Ontario, which is consistent with Nowak’s
(1979:15) finding, based on historical reports, that eastward Coyote expansion
was more rapid through a northern route.
Genetic Composition of the Eastern Coyote Population
Way et al. (2010:10) argue that the “uniform genetic makeup” and minimal
genetic influence from other Canis of the northeastern Coyote population indicate
that it is an “emerging new species” that should be recognized on a par
with other species of North American Canis. The genetic composition of the
northeastern Coyote population does not support this interpretation.
The northeastern Coyote population defined by Way et al. (2010) has a
genetic composition that is about 1/3 Eastern Wolf in both mtDNA sequences
(Kays et al. 2010a, Way et al. 2010) and nuclear microsatellite variation
(Way et al. 2010). Its genetic composition is therefore predominantly Coyote,
but there has been substantial introgression from Eastern Wolves. It is
therefore not a genetically uniform population. Because mtDNA does not
recombine and is maternally inherited, individuals have either the mtDNA
of one species or the other. We cannot discern with mtDNA alone the extent
of hybrid ancestry of any given individual. The nuclear microsatellite DNA
does provide some information on the ancestry of individuals with respect to
the two species. Both STRUCTURE and factorial correspondence analysis
of Way et al. (2010:Figs. 2 and 3) indicate that some northeastern Coyotes
208 Northeastern Naturalist Vol. 17, No. 2
have a microsatellite DNA composition similar to Eastern Wolves, but many
show no Eastern Wolf influence. The northeastern Coyote population is
therefore not uniform, but highly variable with respect to the relative contributions
of the two species to the ancestry of individuals.
The northeastern Coyote population defined by Way et al. (2010) is
also not separate, disjunct, or discrete with respect to other canids. There is
geographic and genetic continuity of northeastern Coyotes and the hybrid
Coyote/Eastern Wolf population of southern Ontario (Grewal et al. 2004,
Kays et al. 2010a, Wilson et al. 2009). The pattern of mtDNA variation in
Coyotes south of the Great Lakes is strongly suggestive of continuity, with
Eastern Wolf influence decreasing in western New York and Pennsylvania,
and absent from a sample of 30 Coyotes from Ohio (Kays et al. 2010a).
Coyotes continued their invasion from the northeast down the Appalachian
Mountains to the south (Nowak 1979:16), so similar genetic continuity from
north to south is also likely.
An alternative interpretation and description of the genetic composition
of Coyotes in eastern North America is that the northeastern Coyote population
defined by Way et al. (2010) is part of a larger population of Coyotes in
eastern North America. It hybridizes (or hybridized) with Eastern Wolves
in southern Quebec and Ontario. The only discernable pattern is a decrease in
genetic influence of Eastern Wolves from eastern New York and Pennsylvania
to Ohio. Overall, the Coyote population of eastern North America is diverse,
with influence of Eastern Wolf introgression probably decreasing from east to
west and north to south. This interpretation is consistent with behavioral and
morphometric studies that suggest the influence of Eastern Wolf hybridization
on northeastern Coyotes, but primarily group them with other Coyotes (Lawrence
and Bossert 1969, Nowak 1979, Silver and Silver 1969).
Schwartz and Vucetich (2009) have made recommendations on the
resolution of questions about defining populations and taxa of Canis in
the Great Lakes region. These include geographic sampling that does not
leave gaps that can lead to misinterpretation of genetic discontinuities, and
the use of a variety of genetic markers to more comprehensively characterize
patterns of geographic variation. Reporting of genetic information on a
finer scale (Schwartz and McKelvey 2009) is needed to confirm possible
genetic discontinuities that might indicate separation of populations. Finerscale
sampling of information from diverse genetic markers (mtDNA,
Y-chromosome haplotypes, and microsatellites) can provide a better understanding
of the relative contributions of different species to the ancestry of
the northeastern Coyote population and its relationship to other Coyotes.
Vernacular Names and Nomenclature
The name “coywolf” was coined by Way et al. (2010) to apply to the
population that they defined in the northeastern United States and eastern
Canada. If common or vernacular names are deemed advantageous for some
purpose, they should accurately describe some attribute of the population to
2010 S.M. Chambers 209
which they are applied. In this case, coywolf implies a group that is as much
or more Eastern Wolf than Coyote, which is not supported by the available
genetic information. The canids in this area should be referred to as Coyotes.
If a more restrictive name is required, I suggest “northeastern Coyote”, but
users should recogonize that these animals are only a part of a larger Coyote
population that extends to the west and south.
Vernacular names can cause unnecessary confusion and controversy
when applied in biological situations that are already complex and contentious,
such as those involving North American canids (e.g., the exchange
on use of the term “Great Lakes wolf ” [Kays et al. 2010b, Wheeldon et
al. 2010]). Coining and application of vernacular names to any convenient
group of populations should be discouraged, unless they apply to taxa that
have been, or are in the final stages of being, formally described as species
or subspecies. Otherwise, these names can misleadingly imply that such
names have taxonomic standing that is not justified. Even when vernacular
names are objectively descriptive and may have some practical use, it must
be recognized that they have no standing under the International Code of
Zoological Nomenclature (ICZN 1999).
Acknowledgments
The manuscript was improved by the constructive comments of two anonymous
reviewers. The findings and conclusions in this article are those of the author and do
not necessarily represent the views of the US Fish and Wildlife Service.
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