Proceedings of the fifth mountain lion workshop: 27

PROCEEDINGS OF THE FIFTH MOUNTAIN LION WORKSHOP 65
of all of the data for a particular specimen. We found that
the small sample size and the sparseness of the data would
not support a CVA of the complete skull morphometry data
set. However, we did analyze the morphometric data relative
to 5 tooth measurements (upper carnassial crown length and
width, lower carnassial crown length, upper canine anteriorposterior,
and maxillary teeth alveolar length). We found
that none of the 4 adjacent subspecies of mountain lions,
including P. c. browni, could be distinguished on the basis of
dentition (Fig.1).
Although morphometrics have traditionally
constituted an important tool in distinguishing among species
and subspecies, a variety of intrinsic characteristics suggest
morphometric data are inherently ambiguous in addressing
variation, particularly at the subspecies or population level.
Both sexual dimorphism (Gay and Best 1995) and
morphometric variation based on age (Gay and Best in press)
are documented in mountain lions. Partitioning data
according to these factors can reduce overall sample size,
which is problematic in populations like P. c. browni and P.
c. improcera, where very few specimens exist. Historically,
one of the more egregious errors committed by taxonomists
has been to describe populations based on a sample
(sometimes as little as a single specimen) inadequate to
describe the extent of morphometric variation within a
population (Engstrom et al. 1994). Furthermore, historic
approaches to describing populations have used discordant
features to distinguish among populations, which only tends
to increase the ambiguity of the subspecies category. More
recent trends in evolutionary biology have suggested a focus
on geographic clines in individual concordant features (Avise
and Ball 1990, O'Brien and Mayr 1991), and the functional
pertinence of these characters relative to their contribution to
the survival and reproduction of the organism (Wilson 1992,
1994).
Recent studies have also demonstrated that
phenotype is highly plastic in some species, and this
plasticity appears to be linked to diet and habitat quality. For
example, a relationship between habitat quality and body size
has been described for black bears (Ursus americanus)
(McCutchen 1993); Stringham 1990, in Craighead et al.
(1995) reported a correlation between weight and skull
length in grizzly bears (Ursus arctos); and phenotypic
plasticity has been offered as one hypothesis to explain
geographic variation in raccoons (Procyon lotor) (Mugaas
and Seidensticker 1993). Rearing environment also appears
to influence the development of some morphological traits in
birds (James 1983). Therefore, some morphometric
characteristics may be limitations imposed on an animal by
its environment rather than adaptations to the environment on
the part of the organism, and these morphometric features
may respond to changes in habitat quality on a short temporal
scale. This suggests that phenotypic variation does not
necessarily reflect genotypic variation, and that phenotypic
characters may converge or diverge between populations
independent of true phylogenetic relationships (Geist 1991).
The degree of plasticity in mountain lion phenotypes has not
been assessed.
Genetics
An exploration of genetic diversity among
mountain lions fell beyond the logistic and fiscal capabilities
of our research. However, ongoing research at the National
Cancer Institute is examining genetic diversity in North and
South American mountain lions, and addressing the
subspecific status of P. c. browni (Steve O'Brien and
Melanie Culver, Genetics Section, Laboratory of Viral
Carcinogens, Frederick, MD, pers. commun.). Preliminary
results indicate little genetic variation in North American
mountain lions in general; results specific to P. c. browni
should be available concomitantly with the publication of
these proceedings.
Researchers have used mitochondrial DNA
(mtDNA) to examine genetic variation at the fine scale
appropriate to the level of subspecies. MtDNA is inherited
maternally, and the rate of evolution in mtDNA is generally
5-10x greater than in nuclear DNA, thus it tends to be highly
polymorphic within species (Hedrick and Miller 1992).
However, it is worth recognizing some of the limitations of
mtDNA data, including the fact that it represents a very
limited part of the gene pool of populations, and that it infers
nothing about adaptive differences between populations
(Cronin 1993). As with morphological analysis, the use of
mtDNA to assess genetic differences requires a sample size
adequate to describe the range of variation within
populations. Obtaining a representative sample from across
the range of a population, particularly one as sparsely
distributed and as cryptic as the mountain lions within the
range of P. c. browni can be expensive and problematic. A
lengthier discussion of the limitations of mtDNA as an
indicator of population status can be found in Cronin (1993).
CONCLUSIONS
Weighting and incorporating the 3 types of data we
have discussed remains a subjective process. Cronin (1993)
proposed that conclusive evidence in any single category
should be sufficient to suggest a population might be
uniquely adapted to its locale, and to manage the population
accordingly. Certainly the most parsimonious approach
would be to evaluate situations on a case-by-case basis and
to manage the preservation of unique adaptations. As
O'Brien and Mayr (1991: 1188) suggested: "The possibility