Proceedings of the fifth mountain lion workshop: 27

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64 PROCEEDINGS OF THE FIFTH MOUNTAIN LION WORKSHOP Table 1. Morphological measurements (mm) of mountain lion skulls collected within the range of the Yuma mountain lion, Puma concolor browni. Measurements were compiled from Grinnell et al. (1937), Hoffmeister (1986), Duke et al. (1987); collection by the authors (specimen 9.4176 and DC); or were provided by museums holding the Nasal Width Lower jaw: greatest length Posterior diameter Upper canine: anterior-posterior Mandible depth Lower carnassials: crown length Upper carnassials: crown width Upper carnassials: crown length Maxillary teeth: alveolar length Nasal length Rostrum width Interorbital breadth Braincase height Postorbital process breadth Mastoid breadth Palate width Palatilar length Basilar length Zygomatic breadth Condylobasal length Greatest length Sex Location Specimen number 27.4 b 108.7 -- 15.1 49.7 18.3 12.2 22.6 b 43.7 49.0 50.8 30.9 71.8 43.1 72.2 61.9 b 62.0 159.7 112.3 156.2 172.3 M MNAZ a 9.4176 30.4 b 123.0 11.1 11.3 -- 15.8 10.7 20.6 67.2 40.5 51.5 38.4 68.6 68.5 77.4 63.8 b 67.7 146.0 126.2 173.0 189.0 F MVZ a 46912 37.6 b 144.0 13.3 13.9 -- 16.2 11.8 21.7 -- 48.0 56.0 43.5 -- -- -- 68.3 b 77.0 -- -- -- -- M MVZ 10586 32.7 b 133.0 12.7 13.3 -- 16.2 10.2 22.5 70.1 45.8 51.1 36.0 74.0 61.0 85.0 65.7 b 76.0 161.0 127.5 178.0 198.0 M MVZ 10587 35.1 b 133.1 -- 15.6 70.0 17.9 12.6 22.6 59.9 55.9 58.3 42.2 79.1 78.7 83.0 41.8 74.4 161.1 148.1 177.7 193.4 M – c DC 15.1 -- 12.8 12.8 -- -- -- -- 55.9 -- 49.8 37.3 -- 67.0 -- 27.5 -- 144.7 124.0 159.0 173.4 F USNM a 203131 17.6 135.0 14.0 14.7 -- 15.5 11.1 20.6 57.5 48.3 55.7 43.5 74.0 43.1 85.0 41.1 -- 165.2 138.0 183.0 205.1 M USNM 125719 21.7 141.2 -- 14.4 -- 15.6 12.0 21.2 60.5 60.3 59.2 41.2 80.5 -- 85.4 63.4 74.8 168.5 134.9 184.8 200.4 M USNM 132482 35.7 b 139.4 -- 15.1 – – -- – 61.3 51.9 57.2 41.8 70.1 76.2 88.5 81.5 b 75.4 168.0 143.1 187.2 205.3 M CM a 22187 a Museum of Northern Arizona (MNAZ), Museum of Vertebrate Zoology (MVZ), U.S. National Museum (USNM), and the Carnegie Museum (CM). b We attribute the discrepancies between these figures and others for the same parameter to our technique for collecting measurements c Private collection
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
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Proceedings of the fifth mountain lion workshop: 27

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