Twelve parameters were measured on skulls of four species of Peromyscus from Arkansas. Univariate statistical tests, multivariate analyses of variance, and principal axis factor analyses were performed on the data set and/or subsets in a search for species-level discriminating characters. Total length of skull was found to discriminate between skulls of P. maniculatis, P. leucopus, and a combined group of P. attwateri and P. gossypinus. Furthermore, the ratio of interorbital width and length of nasal bone was found to adequately discriminate between skulls of P. attwateri and P. gossypinus

McDaniel, V. Rick

McLarty, Phil

Tumlison, C. Renn

English

UARK (University of Arkansas )

Journal of the Arkansas Academy of Science Volume 37 Article 15 1983 Mensural Discrimination of the Skulls of Arkansas Peromyscus V. Rick McDaniel Arkansas State University C. Renn Tumlison Arkansas State University Phil McLarty Arkansas State University Follow this and additional works at: https://scholarworks.uark.edu/jaas  Part of the Zoology Commons Recommended Citation McDaniel, V. Rick; Tumlison, C. Renn; and McLarty, Phil (1983) "Mensural Discrimination of the Skulls of Arkansas Peromyscus," Journal of the Arkansas Academy of Science: Vol. 37 , Article 15. Available at: https://scholarworks.uark.edu/jaas/vol37/iss1/15 This article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0). Users are able to read, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking prior permission from the publisher or the author. This Article is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Journal of the Arkansas Academy of Science by an authorized editor of ScholarWorks@UARK. For more information, please contact scholar@uark.edu. 50 Arkansas Academy of Science Proceedings, Vol. XXXVII,1983MENSURAL DISCRIMINATIONOF THESKULLS OF ARKANSAS PEROMYSCUSV. RICK MCDANIEL,RENN TUMLISONand PHIL MCLARTYDepartment of Biological ScienceArkansas State UniversityState University, Arkansas 72467ABSTRACTTwelve parameters were measured on skulls of four species of Peromyscus from Arkansas. Univariatestatistical tests, multivariate analyses of variance, and principal axis factor analyses were performed onthe data set and/or subsets in a search for species-level discriminating characters. Total lengthof skullwas found to discriminate between skulls of P. maniculatis, P. leucopus, and a combined group ofP. attwateri and P. gossypinus. Furthermore, the ratio of interorbital width and lengthof nasal bonewas found to adequately discriminate between skulls of P. attwateri and P. gossypinus.INTRODUCTIONIndividual specimens of white-footed mice (Peromyscus) arenotoriously difficult to discriminate to the species level from regionscontaining two or more species (Choate, 1973; Choate et al., 1979;Thompson and Conley, 1983). Arkansas is such a region, with fourspecies ofPeromyscus ranging throughout at least portions of the state(Sealander, 1979): the deer mouse, P. maniculatus (Wagner), the smallestmember of the group and normally having a well furred, short, anddistinctly bicolored tail; the white-footed mouse, P. leucopus (Rafines-que), somewhat larger and having a relatively longer and less furredtail; the Texas mouse, P. attwateri J. A.Allen,a large member of thegenus and having a long and terminally tufted tail; and thecotton mouse,P. gossypinus (LeConte), another large member of the genus andhaving a tail with no terminal tuft. Aclosely related species, the goldenmouse, Ochrotomys nuttalli (Harlan), superficially complicates theidentification dilema, but is readily discriminated by its more posteriorlylyingposterior palatal foramen and its anteriorly perpendicular infra-orbital plate (Lowery, 1974).While the skins ofspecimens of the four species ofPeromyscus are,withpractice, relatively easy to discriminate among, and while the speciesare fairlydistinct ecologically (Sealander, 1979; Schwartz and Schwartz,1981), attempts to accurately identify individual skulls can be frustratingand may result in only low probabilities ofaccurate classification. Thisstudy, then, was designed to search for a character and/or group ofcharacters that would, with a very highdegree ofprobability ofaccuracy,discriminate among the skulls of the four Arkansas species ofPeromyscus.METHODS ANDMATERIALSAdult, unbroken skulls of both sexes were selected from clearlydiagnostic skins. Specimens were from throughout the Arkansas rangesof the species, and all are housed in the Collection of RecentMammals of the Arkansas State University Museum of Zoology(ASUMZ). Our sample included: 41 specimens of P. maniculatus, 41specimens ofP. leucopus, 40 specimens ofP. attwateri, and 31 specimensof P. gossypinus.Twelve parameters were measured on each skull to the nearest 20thofamm with dial calipers. Parameters were as defined by DeBlase andMartin (1974) and included: (A)length ofmaxillary tooth row, (B)totallengthof skull, (C) basonasal length, (D)breadth of palate at molarone, (E) breadth of palate at molar three, (F) width of interorbitalconstriction, (G) length ofbony palate, (H) lengthof nasal bone, (I)zygomatic breadth, (J) greatest rostral width, (K)breadth ofbraincase,and (L)length of anterior palatine foramen.Allnumerical analyses were performed onSAS (SAS Institute Inc.,1979) through the University ofArkansas Computing Center. Analysesincluded routines computing simple univariate statistics, multivariateanalyses of variance (acronymed MANOVA), and principal axisfactor analyses.RESULTS ANDDISCUSSIONInvestigation began with a multivariate analysis of variance performedon a combined data set of all four species. All12 variables generatedhigh F-values indicating that significant (at the 0.0001 level) variationexisted among the species over all variables. MANOVAwas followedby principal axis factor analysis on the combined data set. Factor loadingscores were plotted along the first two principal factor axes (Fig. 1).Figure 1.Factor loading scores for four species ofPeromyscus plottedalong the first and second principal factor axes. Alphabetic characters(A-L) as defined inMethods and Materials.50Journal of the Arkansas Academy of Science, Vol. 37 [1983], Art. 15Published by Arkansas Academy of Science, 1983Arkansas Academy of Science Proceedings, Vol. XXXVII,1983 51V. Rick McDaniel, Renn Tumlison, and Phil McClartyAll variables correlated highly(0.7 or higher) with the first principalaxis, and only weakly with the second principal axis ( <0.5). Thisfactor pattern is typical forcraniometric data and suggests that factoraxis 1 represents an axis ofgeneral skull size. Factor axis 1accountedfor 80.2% of the observed variation, while the second factor axisaccounted foronly an additional 6.3% of the observed variation. Thelack ofany wellcorrelated variables prevents a reasonable biologicalinterpretation of factor axis 2.Aplot of factor scores by species along the first and second prin-cipal factor axes revealed good separation along factor axis 1 of P.maniculatus, P. leucopus, and a combined group ofP. attwateri andp. gossypinus (Fig. 2). In a multivariate sense, then, skulls ofArkansas specimens ofPeromyscus can be reliably discriminated asbelonging to one of three groups on the basis of general size. In thisscheme, thesmallest skulls are ofP. maniculatus, the intermediate skullsare of P. leucopus, and the largest skulls are of P. attwateri and/orP. gossypinus.Insubsequent analyses, relationships and multivariate overlaps ofpairs ofspecies were examined more closely. Although some degree ofoverlap existed among factor scores ofP. maniculatus and P. leucopus(Fig. 3), the degree ofoverlap is quite small (ina multivariate sense)and discrimination at the species level is acceptably reliable as indicatedby MANOVA generated F values at the 0.0001 level. Never-the-less,a check ofunivariate data revealed that no single parameter totallydiscriminates between the two species. Several characters, though,approached good (95% level)discriminatory power, includinggreatestlength of skull (Fig. 4).Slight overlap also existed among factor scores of P. leucopus andP. attwateri (Fig. 5). Again, multivariate overlap was slight andMANOVAgenerated F values were high forall variables except lengthofbony palate and greatest rostral width. Greatest length ofskull againdiscriminated between the species at the 95% level (Fig. 4).At this point, only P. attwateri and P. gossypinus remained to bediscriminated between. Examination ofa plot offactor loading scoresfor these species (Fig. 6) revealed a considerably different pattern ofvariation than that observed for all four species together (Fig. 1).Factor axis 1 appears to be related to parameters of skull length, whilefactor axis 2 appears to correlate best with parameters ofpost-nasalwidth ofthe skull. Aplot ofthe factor scores of these two species (Fig.7) revealed only fair separation along factor axis 1. Overlap of the speciesappeared tobe visuallysignificant, and in fact, two specimens (6% ofthe sample) ofP. gossypinus and four specimens (10% of the sample)of P. attwateri are represented in the overlap zone. Testing byMANOVA,however, revealed significant differences between the speciesFigure 4. Bar-histogram of values for total lengthof skull for four speciesofPeromyscus. The mean and two standard deviation units either sideof the mean are included.Eure2. Factor scores by species plotted along the first and secondicipal factor axes. Polygons represent outlined perimeter values forh species and large dots represent mean values foreach species. 1P. maniculatus, 2 = P. leucopus, 3 = P. attwateri, and 4 = P.sypinus.Figure 5. Factor scores ofP. leucopus and P. attwateri, as representedon Fig. 2.rire3. Factor scores ofP. maniculatus and P. leucopus, as representedFigure 2.51Journal of the Arkansas Academy of Science, Vol. 37 [1983], Art. 15https://scholarworks.uark.edu/jaas/vol37/iss1/15Mensural Discrimination of the Skulls of Arkansas PeromyscusFigure 9. Key to the skulls ofArkansas specimens of Peromyscus,Inan attempt to further discriminate among the skulls ofP. attwateriand P. gossypinus, ratios were computed of one parameter againstanother. Eventually, the ratio demonstrating the highest discriminatorypower turned out tobe minimum interorbital distance divided by lengthof the nasal bone (Fig. 8).As a result of these analyses, it was possible to prepare a key (Fig.9) to the adult skulls ofspecies ofPeromyscus occurring in Arkansasand having at least a 95% reliability factor. Total length of skulldiscriminates between P. maniculatus (X=22.8mm), P. leucopus(X"=25.4mm), and a combined group ofP. attwateri (X =27.7mm) andP. gossypinus (X =28.7mm). The ratio ofinterorbital widthand lengthof nasal bone discriminates reasonably well between skulls of P.attwateri (0.41 to 0.48) and P. gossypinus (0.33 to 0.41).Finally, it must be stressed that results of this analysis are fullypredicated on the assumption that initial discrimination among thesespecies was correct. To validate this assumption, specimens wereintentionally selected only when skin characteristics made specific assign-ment positive. A potential problem inherent in this process would bethe imposition ofartificiallimits to the cranial variation present inthesamples. It seems doubtful, though, that limits imposed by skincharacteristics would represent limits ofcraniometric variation as wellInterestingly, examination of coefficient of variation values revealedthat for all variables except breadth of palate at molar three, skulls olP. maniculatus generated the highest values. For breadth ofpalate aimolar three, skulls ofP. leucopus generated the highest value.SUMMARYWhile the skulls of the species ofPeromyscus occurring inArkansasare difficult to distinguish between, total length ofskull willdiscriminatebetween P. maniculatus, P. leucopus, and a combined group of P.attwateri and P. gossypinus. Subsequently, the ratio ofinterorbital widthand length ofnasal bone willadequately discriminate between skullsofP. attwateri and P. gossypinus.ACKNOWLEDGMENTThe authors thank J. D. and M. R. Wilhide for theirunselfish help during several phases of this project.Figure 6. Factor loading scores forP. attwateri and P. gossypinus plottedalong the firstand second principal factor axes. Alphabetic charactersas inFig. 1.Figure 7. Factor scores ofP. attwateri and P. gossypinus, as representedonFig. 2. The dashed perpendicular line represents the mid-point alongaxis 1between the means ofthe two species. The heavy arrows indicatethe number of individuals from the samples falling beyond the mid-point.at the 0.0001 level forall parameters except breadth ofpalate at molarsone and three and length ofbony palate. However, character overlapwas extensive and univariate examination revealed no single parameterhaving 95% discriminatory power for the skulls of these two species.Two characters, length of nasal bone and greatest rostral width,correlating highly with the first factor axis, had some discriminatorypower (80-90%).52 Arkansas Academy of Science Proceedings, Vol. XXXVII,198352Journal of the Arkansas Academy of Science, Vol. 37 [1983], Art. 15Published by Arkansas Academy of Science, 1983Arkansas Academy of Science Proceedings, Vol. XXXVII,1983 53V. Rick McDaniel, Renn Tumlison, and Phil McClartyLITERATURE CITEDr)ATE, J. R. 1973. Identification and Recent distribution ofwhite-footed mice (Peromyscus) in New England. J. Mamm.54:41-49.CHOATE, J. R., R. C. DOWLER, and J. E. KRAUSE. 1979.Mensural discrimination between Peromyscus leucopus and P.maniculatus (Rodentia) in Kansas. Southw. Nat. 24:249-258.DEBLASE, A.F., and R. E. MARTIN.1974. Amanual of mammalogywith keys to families of the world. Wm. C. Brown Co.,Dubuque.LOWERY, G. H., JR. 1974. The mammals of Louisiana and itsadjacent waters. Louisiana State Univ.Press Baton Rouge. 565 pp.SAS INSTITUTEINC. 1979. SAS user's guide 1979 edition. Cary,N.C. 494 pp.SCHWARTZ, C. W., and E. R. SCHWARTZ. 1981. The wildmammals of Missouri. Revised Ed. Univ.Mo.Press and Mo.Dept.Cons. Columbia.SEALANDER, J. A. 1979. A guide to Arkansas mammals. RiverRoad Press. Conway, AR. 313 pp.THOMPSON, T. G., and W. CONLEY. 1983. Discrimination ofcoexisting species of Peromyscus in south-central New Mexico.Southw. Nat. 28:199-209.53Journal of the Arkansas Academy of Science, Vol. 37 [1983], Art. 15https://scholarworks.uark.edu/jaas/vol37/iss1/15

Mensural Discrimination of the Skulls of Arkansas Peromyscus

ScholarWorks@UARK

Journal of the Arkansas Academy of ScienceVolume 37 Article 151983Mensural Discrimination of the Skulls of ArkansasPeromyscusV. Rick McDanielArkansas State UniversityC. Renn TumlisonArkansas State UniversityPhil McLartyArkansas State UniversityFollow this and additional works at: http://scholarworks.uark.edu/jaasPart of the Zoology CommonsThis article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0). Users are able toread, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking priorpermission from the publisher or the author.This Article is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Journal of the Arkansas Academyof Science by an authorized editor of ScholarWorks@UARK. For more information, please contact scholar@uark.edu, ccmiddle@uark.edu.Recommended CitationMcDaniel, V. Rick; Tumlison, C. Renn; and McLarty, Phil (1983) "Mensural Discrimination of the Skulls of Arkansas Peromyscus,"Journal of the Arkansas Academy of Science: Vol. 37 , Article 15.Available at: http://scholarworks.uark.edu/jaas/vol37/iss1/1550 Arkansas Academy of Science Proceedings, Vol. XXXVII,1983MENSURAL DISCRIMINATIONOF THESKULLS OF ARKANSAS PEROMYSCUSV. RICK MCDANIEL,RENN TUMLISONand PHIL MCLARTYDepartment of Biological ScienceArkansas State UniversityState University, Arkansas 72467ABSTRACTTwelve parameters were measured on skulls of four species of Peromyscus from Arkansas. Univariatestatistical tests, multivariate analyses of variance, and principal axis factor analyses were performed onthe data set and/or subsets in a search for species-level discriminating characters. Total lengthof skullwas found to discriminate between skulls of P. maniculatis, P. leucopus, and a combined group ofP. attwateri and P. gossypinus. Furthermore, the ratio of interorbital width and lengthof nasal bonewas found to adequately discriminate between skulls of P. attwateri and P. gossypinus.INTRODUCTIONIndividual specimens of white-footed mice (Peromyscus) arenotoriously difficult to discriminate to the species level from regionscontaining two or more species (Choate, 1973; Choate et al., 1979;Thompson and Conley, 1983). Arkansas is such a region, with fourspecies ofPeromyscus ranging throughout at least portions of the state(Sealander, 1979): the deer mouse, P. maniculatus (Wagner), the smallestmember of the group and normally having a well furred, short, anddistinctly bicolored tail; the white-footed mouse, P. leucopus (Rafines-que), somewhat larger and having a relatively longer and less furredtail; the Texas mouse, P. attwateri J. A.Allen,a large member of thegenus and having a long and terminally tufted tail; and thecotton mouse,P. gossypinus (LeConte), another large member of the genus andhaving a tail with no terminal tuft. Aclosely related species, the goldenmouse, Ochrotomys nuttalli (Harlan), superficially complicates theidentification dilema, but is readily discriminated by its more posteriorlylyingposterior palatal foramen and its anteriorly perpendicular infra-orbital plate (Lowery, 1974).While the skins ofspecimens of the four species ofPeromyscus are,withpractice, relatively easy to discriminate among, and while the speciesare fairlydistinct ecologically (Sealander, 1979; Schwartz and Schwartz,1981), attempts to accurately identify individual skulls can be frustratingand may result in only low probabilities ofaccurate classification. Thisstudy, then, was designed to search for a character and/or group ofcharacters that would, with a very highdegree ofprobability ofaccuracy,discriminate among the skulls of the four Arkansas species ofPeromyscus.METHODS ANDMATERIALSAdult, unbroken skulls of both sexes were selected from clearlydiagnostic skins. Specimens were from throughout the Arkansas rangesof the species, and all are housed in the Collection of RecentMammals of the Arkansas State University Museum of Zoology(ASUMZ). Our sample included: 41 specimens of P. maniculatus, 41specimens ofP. leucopus, 40 specimens ofP. attwateri, and 31 specimensof P. gossypinus.Twelve parameters were measured on each skull to the nearest 20thofamm with dial calipers. Parameters were as defined by DeBlase andMartin (1974) and included: (A)length ofmaxillary tooth row, (B)totallengthof skull, (C) basonasal length, (D)breadth of palate at molarone, (E) breadth of palate at molar three, (F) width of interorbitalconstriction, (G) length ofbony palate, (H) lengthof nasal bone, (I)zygomatic breadth, (J) greatest rostral width, (K)breadth ofbraincase,and (L)length of anterior palatine foramen.Allnumerical analyses were performed onSAS (SAS Institute Inc.,1979) through the University ofArkansas Computing Center. Analysesincluded routines computing simple univariate statistics, multivariateanalyses of variance (acronymed MANOVA), and principal axisfactor analyses.RESULTS ANDDISCUSSIONInvestigation began with a multivariate analysis of variance performedon a combined data set of all four species. All12 variables generatedhigh F-values indicating that significant (at the 0.0001 level) variationexisted among the species over all variables. MANOVAwas followedby principal axis factor analysis on the combined data set. Factor loadingscores were plotted along the first two principal factor axes (Fig. 1).Figure 1.Factor loading scores for four species ofPeromyscus plottedalong the first and second principal factor axes. Alphabetic characters(A-L) as defined inMethods and Materials.50Journal of the Arkansas Academy of Science, Vol. 37 [1983], Art. 15Published by Arkansas Academy of Science, 1983Arkansas Academy of Science Proceedings, Vol. XXXVII,1983 51V. Rick McDaniel, Renn Tumlison, and Phil McClartyAll variables correlated highly(0.7 or higher) with the first principalaxis, and only weakly with the second principal axis ( <0.5). Thisfactor pattern is typical forcraniometric data and suggests that factoraxis 1 represents an axis ofgeneral skull size. Factor axis 1accountedfor 80.2% of the observed variation, while the second factor axisaccounted foronly an additional 6.3% of the observed variation. Thelack ofany wellcorrelated variables prevents a reasonable biologicalinterpretation of factor axis 2.Aplot of factor scores by species along the first and second prin-cipal factor axes revealed good separation along factor axis 1 of P.maniculatus, P. leucopus, and a combined group ofP. attwateri andp. gossypinus (Fig. 2). In a multivariate sense, then, skulls ofArkansas specimens ofPeromyscus can be reliably discriminated asbelonging to one of three groups on the basis of general size. In thisscheme, thesmallest skulls are ofP. maniculatus, the intermediate skullsare of P. leucopus, and the largest skulls are of P. attwateri and/orP. gossypinus.Insubsequent analyses, relationships and multivariate overlaps ofpairs ofspecies were examined more closely. Although some degree ofoverlap existed among factor scores ofP. maniculatus and P. leucopus(Fig. 3), the degree ofoverlap is quite small (ina multivariate sense)and discrimination at the species level is acceptably reliable as indicatedby MANOVA generated F values at the 0.0001 level. Never-the-less,a check ofunivariate data revealed that no single parameter totallydiscriminates between the two species. Several characters, though,approached good (95% level)discriminatory power, includinggreatestlength of skull (Fig. 4).Slight overlap also existed among factor scores of P. leucopus andP. attwateri (Fig. 5). Again, multivariate overlap was slight andMANOVAgenerated F values were high forall variables except lengthofbony palate and greatest rostral width. Greatest length ofskull againdiscriminated between the species at the 95% level (Fig. 4).At this point, only P. attwateri and P. gossypinus remained to bediscriminated between. Examination ofa plot offactor loading scoresfor these species (Fig. 6) revealed a considerably different pattern ofvariation than that observed for all four species together (Fig. 1).Factor axis 1 appears to be related to parameters of skull length, whilefactor axis 2 appears to correlate best with parameters ofpost-nasalwidth ofthe skull. Aplot ofthe factor scores of these two species (Fig.7) revealed only fair separation along factor axis 1. Overlap of the speciesappeared tobe visuallysignificant, and in fact, two specimens (6% ofthe sample) ofP. gossypinus and four specimens (10% of the sample)of P. attwateri are represented in the overlap zone. Testing byMANOVA,however, revealed significant differences between the speciesFigure 4. Bar-histogram of values for total lengthof skull for four speciesofPeromyscus. The mean and two standard deviation units either sideof the mean are included.Eure 2. Factor scores by species plotted along the first and secondicipal factor axes. Polygons represent outlined perimeter values forh species and large dots represent mean values foreach species. 1P. maniculatus, 2 = P. leucopus, 3 = P. attwateri, and 4 = P.sypinus.Figure 5. Factor scores ofP. leucopus and P. attwateri, as representedon Fig. 2.rire3. Factor scores ofP. maniculatus and P. leucopus, as representedFigure 2.51Journal of the Arkansas Academy of Science, Vol. 37 [1983], Art. 15http://scholarworks.uark.edu/jaas/vol37/iss1/15Mensural Discrimination of the Skulls of Arkansas PeromyscusFigure 9. Key to the skulls ofArkansas specimens of Peromyscus,Inan attempt to further discriminate among the skulls ofP. attwateriand P. gossypinus, ratios were computed of one parameter againstanother. Eventually, the ratio demonstrating the highest discriminatorypower turned out tobe minimum interorbital distance divided by lengthof the nasal bone (Fig. 8).As a result of these analyses, it was possible to prepare a key (Fig.9) to the adult skulls ofspecies ofPeromyscus occurring in Arkansasand having at least a 95% reliability factor. Total length of skulldiscriminates between P. maniculatus (X=22.8mm), P. leucopus(X"=25.4mm), and a combined group ofP. attwateri (X =27.7mm) andP. gossypinus (X =28.7mm). The ratio ofinterorbital widthand lengthof nasal bone discriminates reasonably well between skulls of P.attwateri (0.41 to 0.48) and P. gossypinus (0.33 to 0.41).Finally, it must be stressed that results of this analysis are fullypredicated on the assumption that initial discrimination among thesespecies was correct. To validate this assumption, specimens wereintentionally selected only when skin characteristics made specific assign-ment positive. A potential problem inherent in this process would bethe imposition ofartificiallimits to the cranial variation present inthesamples. It seems doubtful, though, that limits imposed by skincharacteristics would represent limits ofcraniometric variation as wellInterestingly, examination of coefficient of variation values revealedthat for all variables except breadth of palate at molar three, skulls olP. maniculatus generated the highest values. For breadth ofpalate aimolar three, skulls ofP. leucopus generated the highest value.SUMMARYWhile the skulls of the species ofPeromyscus occurring inArkansasare difficult to distinguish between, total length ofskull willdiscriminatebetween P. maniculatus, P. leucopus, and a combined group of P.attwateri and P. gossypinus. Subsequently, the ratio ofinterorbital widthand length ofnasal bone willadequately discriminate between skullsofP. attwateri and P. gossypinus.ACKNOWLEDGMENTThe authors thank J. D. and M. R. Wilhide for theirunselfish help during several phases of this project.Figure 6. Factor loading scores forP. attwateri and P. gossypinus plottedalong the firstand second principal factor axes. Alphabetic charactersas inFig. 1.Figure 7. Factor scores ofP. attwateri and P. gossypinus, as representedonFig. 2. The dashed perpendicular line represents the mid-point alongaxis 1between the means ofthe two species. The heavy arrows indicatethe number of individuals from the samples falling beyond the mid-point.at the 0.0001 level forall parameters except breadth ofpalate at molarsone and three and length ofbony palate. However, character overlapwas extensive and univariate examination revealed no single parameterhaving 95% discriminatory power for the skulls of these two species.Two characters, length of nasal bone and greatest rostral width,correlating highly with the first factor axis, had some discriminatorypower (80-90%).52 Arkansas Academy of Science Proceedings, Vol. XXXVII,198352Journal of the Arkansas Academy of Science, Vol. 37 [1983], Art. 15Published by Arkansas Academy of Science, 1983Arkansas Academy of Science Proceedings, Vol. XXXVII,1983 53V. Rick McDaniel, Renn Tumlison, and Phil McClartyLITERATURE CITEDr)ATE, J. R. 1973. Identification and Recent distribution ofwhite-footed mice (Peromyscus) in New England. J. Mamm.54:41-49.CHOATE, J. R., R. C. DOWLER, and J. E. KRAUSE. 1979.Mensural discrimination between Peromyscus leucopus and P.maniculatus (Rodentia) in Kansas. Southw. Nat. 24:249-258.DEBLASE, A.F., and R. E. MARTIN.1974. Amanual of mammalogywith keys to families of the world. Wm. C. Brown Co.,Dubuque.LOWERY, G. H., JR. 1974. The mammals of Louisiana and itsadjacent waters. Louisiana State Univ.Press Baton Rouge. 565 pp.SAS INSTITUTEINC. 1979. SAS user's guide 1979 edition. Cary,N.C. 494 pp.SCHWARTZ, C. W., and E. R. SCHWARTZ. 1981. The wildmammals of Missouri. Revised Ed. Univ.Mo.Press and Mo.Dept.Cons. Columbia.SEALANDER, J. A. 1979. A guide to Arkansas mammals. RiverRoad Press. Conway, AR. 313 pp.THOMPSON, T. G., and W. CONLEY. 1983. Discrimination ofcoexisting species of Peromyscus in south-central New Mexico.Southw. Nat. 28:199-209.53Journal of the Arkansas Academy of Science, Vol. 37 [1983], Art. 15http://scholarworks.uark.edu/jaas/vol37/iss1/15

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Mensural Discrimination of the Skulls of Arkansas Peromyscus

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