Revisiting Primate Masticatory Scaling Relationships · Theropithecus gelada Colobus polykomos...
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Male Regression Results Female Regression Results Revisiting Primate Masticatory Scaling Relationships Sarah Cumpston and Claire E. Terhune Department of Anthropology, University of Arkansas, Fayetteville, Arkansas Regression Results When All Taxa are Considered X Y Slope of Isometry RMA Slope Result Mandible Length Condyle Width 1.00 1.06 (±0.09) Isometry Condyle Length 1.00 1.04 (±0.09) Isometry Condyle Area 2.00 2.07 (±0.19) Isometry Mandible Width 1.00 0.97 (±0.11) Isometry Mandible Height 1.00 1.07 (±0.11) Isometry Body Mass Mandible Length 0.33 0.37 (±0.04) Isometry Condyle Width 0.33 0.39 (±0.05) Positive Condyle Length 0.33 0.38 (±0.05) Isometry Condyle Area 0.66 0.76 (±0.10) Positive Mandible Width 0.33 0.36 (±0.05) Isometry Mandible Height 0.33 0.39 (±0.06) Positive Research Questions In this study we examined the following questions 1. Are the data phylogenetically patterned and how are the results affected when statistically accounting for phylogeny? 2. Do masticatory scaling patterns differ in males and females? 3. How do scaling patterns differ among platyrrhines, cercopithecoids, and hominoids? Materials • Mean species/sex body mass drawn from Smith and Jungers (1997) • Condylar and mandibular measurements from Terhune (2010) Introduction Previous work on the masticatory apparatus (e.g., Bouvier, 1986a,b; Hylander, 1985; Jungers et al., 1995) has demonstrated unique scaling patterns in the temporomandibular joint (TMJ) and mandible of both platyrrhines and cercopithecoids that can be linked to dietary behaviors. For example, folivory and ingestion of large, tough fruits in cercopithecoids (Bouvier, 1986b; Smith et al., 1983) has been demonstrated to be positively correlated with their deeper mandibles and wider condyles. However, these adaptations are not shared by folivorous platyrrhines (Bouvier, 1986a), suggesting a phylogenetic component to the observed variation. Notably, these studies did not take into account the phylogenetic relationships among species, did not include hominoids (and assessed cercopithecines and platyrrhines separately), and only evaluated males or females without consideration of both sexes. Females were initially analyzed separately from males in Bouvier (1986a:553) but were removed when it was concluded that “few statistically significant differences were found between the scaling patterns of the two sexes”. In this study, we analyze a broad sample of anthropoid primates to determine the role of phylogeny and sexual dimorphism in masticatory scaling. Methods • RMA regressions (Smith, 2009) of condyle and corpus measurements against both mandible length (as a measure of the masticatory lever arm )and body mass (as an indicator of the overall size of the animal) (i.e., Hylander, 1985; Vinyard, 2008) • Males and females were analyzed separately; analyses were initially performed on all taxa and then for platyrrhines, cercopithecoids, and hominoids separately • All data were log transformed for analysis Literature Cited Bouvier M. 1986a. Int J Prim 7: 551-567 Bouvier M. 1986b. AJPA 69 :473-482 Hylander W. 1985. Am Zool 25:315-330 Smith RJ. 2009. AJPA 140: 476-486 Smith J, Jungers W. 1997. JHE 32:523-559 Terhune C. 2010. Ph.D. Diss, ASU Vinyard C. 2008. In: Prim Craniofac Func Biol, pp. 357-385 . Contact [email protected] [email protected] Terhunelab.uark.edu Acknowledgements Funding for this research was initially provided by NSF (BCS 0752661) and The Leakey Foundation (grants to CET). Thanks to the American Museum of Natural History, the Department of Primatology at the State Collection of Anthropology and Paleoanatomy, the National Museum of Natural History, the Field Museum, and the Royal Museum for Central Africa for access to their primate collections. Results • All regressions were significant (p<0.0016) with r 2 >0.741 (all taxa) or r 2 >0.65 (clades separated) • A strong phylogenetic signal was found for most relationships • Condylar variables (length, width, area) tend to be positively allometric, whereas mandibular measurements were more likely to scale with isometry Cercopithecus mitis Cercopithecus nictitans Erythrocebus patas Miopithecus talapoin Alouatta belzebul Alouatta palliata Alouatta seniculus Ateles geoffroyi Lagothrix lagotricha Aotus trivirgatus Cebus albifrons Cebus apella Cebus capucinus Saimiri sciureus Gorilla beringei Gorilla gorilla gorilla Homo sapiens Hylobates agilis Hylobates klossii Hylobates lar Pan paniscus Pan troglodytes schweinfurthii Pan troglodytes troglodytes Pan troglodytes verus Pongo abelii Pongo pygmaeus Symphalangus syndactylus Cacajao melanocephalus Pithecia pithecia Cercocebus torquatus Lophocebus albigena Macaca fascicularis Macaca nemestrina Mandrillus sphinx Papio anubis Papio cynocephalus Papio ursinus Theropithecus gelada Colobus polykomos Nasalis larvatus Piliocolobus badius Procolobus verus Semnopithecus entellus Trachypithecus obscurus Total Species = 44 Platyrrhines =12 Cercopithecoids = 19 Hominoids = 13 Λ*, Strength of the phylogenetic signal approximated 0-1 Sex X Y All Platy. Cerco. Hom. Female Mandible Length Condyle Width 0.91 0.00 0.67 0.00 Condyle Length 0.86 0.00 0.00 0.00 Condyle Area 0.92 0.31 0.42 0.00 Mandible Width 1.00 0.00 0.85 1.00 Mandible Height 0.99 1.00 0.00 1.00 Body Mass Mandible Length 0.95 1.00 1.00 0.90 Condyle Width 0.87 0.92 0.74 0.00 Condyle Length 0.87 0.83 0.83 0.63 Condyle Area 0.89 0.88 0.76 0.51 Mandible Width 0.96 1.00 1.00 0.56 Mandible Height 0.95 1.00 1.00 0.69 Male Mandible Length Condyle Width 0.95 0.00 0.71 0.00 Condyle Length 0.90 0.00 0.00 0.00 Condyle Area 0.95 0.00 0.59 0.00 Mandible Width 0.99 1.00 1.00 1.00 Mandible Height 1.00 1.00 0.98 1.00 Body Mass Mandible Length 0.92 0.97 0.94 0.00 Condyle Width 0.76 0.91 0.70 0.00 Condyle Length 0.87 1.00 0.81 0.00 Condyle Area 0.86 1.00 0.77 0.00 Mandible Width 0.91 1.00 0.97 0.00 Mandible Height 0.92 0.82 0.89 0.43 *a value of 0 signifying no signal, 1 signifying a strong signal Regression Results When All Taxa are Considered X Y Slope of Isometry RMA Slope Result Mandible Length Condyle Width 1.00 1.20 (±0.13) Positive Condyle Length 1.00 1.12 (±0.11) Positive Condyle Area 2.00 2.28 (±0.26) Positive Mandible Width 1.00 1.10 (±0.14) Isometry Mandible Height 1.00 1.07 (±0.14) Isometry Body Mass Mandible Length 0.33 0.36 (±0.05) Isometry Condyle Width 0.33 0.43 (±0.07) Positive Condyle Length 0.33 0.40 (±0.06) Positive Condyle Area 0.66 0.81 (±0.13) Positive Mandible Width 0.33 0.39 (±0.07) Isometry Mandible Height 0.33 0.38 (±0.07) Isometry 3.5 4.0 4.5 5.0 1.0 1.5 2.0 2.5 Mandible Length Condyle Length 3.5 4.0 4.5 5.0 2.0 2.5 3.0 3.5 Mandible Length Condyle Width 3.5 4.0 4.5 5.0 2.5 3.5 4.5 5.5 Mandible Length Condyle Area 3.5 4.0 4.5 5.0 1.5 2.0 2.5 3.0 Mandible Length Mandible Width 7 8 9 10 11 3.5 4.0 4.5 5.0 Body Mass Mandible Length 7 8 9 10 11 2.0 2.5 3.0 3.5 Body Mass Condyle Width 7 8 9 10 11 1.0 1.5 2.0 2.5 Body Mass Condyle Length 7 8 9 10 11 2.5 3.5 4.5 5.5 Body Mass Condyle Area 3.5 4.0 4.5 5.0 2.0 2.5 3.0 3.5 Mandible Length Condyle Width 3.5 4.0 4.5 5.0 1.0 1.5 2.0 2.5 Mandible Length Condyle Length 3.5 4.0 4.5 5.0 2.5 3.5 4.5 5.5 Mandible Length Condyle Area 3.5 4.0 4.5 5.0 1.5 2.0 2.5 3.0 Mandible Length Mandible Width 7 8 9 10 11 12 3.5 4.0 4.5 5.0 Body Mass Mandible Length 7 8 9 10 11 12 2.0 2.5 3.0 3.5 Body Mass Condyle Width 7 8 9 10 11 12 1.0 1.5 2.0 2.5 Body Mass Condyle Length 7 8 9 10 11 12 2.5 3.5 4.5 5.5 Body Mass Condyle Area Measurements of the mandible utilized by Bouvier (1986a) and employed here. Discussion These results indicate the data are phylogenetically patterned (RQ1), males and females do show different scaling patterns (RQ2), and masticatory scaling patterns vary across clades (RQ3). • Platyrrhine males and females show the same general pattern of isometric scaling relationships with the exception of a significant positive allometry of condylar area on body mass in females. • Cercopithecoids demonstrated more variation between males and females than platyrrhines. Notably, in cercopithecoid males mandible width vs. mandible length was negatively allometric while females demonstrated isometry. Males cercopithecoids demonstrated positive allometry in mandible height on body mass. • Hominoids primarily scale with positive allometry, with strong positive allometry in condylar width, length, and area in females and condylar area in males. Our results suggest that the previous analysis (Bouvier, 1986a,b), though sufficient at the time, can be improved upon by incorporating phylogenetic methods as well as including hominoids and females. These revised analyses indicate that masticatory scaling patterns vary considerably across sexes and clades, potentially in relation to dietary or other behavioral differences . Platyrrhini Cercopithecoidea Hominoidea
Transcript of Revisiting Primate Masticatory Scaling Relationships · Theropithecus gelada Colobus polykomos...
Male Regression Results
Female Regression Results
Revisiting Primate Masticatory Scaling RelationshipsSarah Cumpston and Claire E. TerhuneDepartment of Anthropology, University of Arkansas, Fayetteville, Arkansas
Regression Results When All Taxa are Considered
X YSlope of Isometry RMA Slope Result
Man
dib
le
Len
gth
Condyle Width 1.00 1.06 (±0.09) Isometry
Condyle Length 1.00 1.04 (±0.09) Isometry
Condyle Area 2.00 2.07 (±0.19) Isometry
Mandible Width 1.00 0.97 (±0.11) Isometry
Mandible Height 1.00 1.07 (±0.11) Isometry
Bo
dy
Mas
s
Mandible Length 0.33 0.37 (±0.04) Isometry
Condyle Width 0.33 0.39 (±0.05) Positive
Condyle Length 0.33 0.38 (±0.05) Isometry
Condyle Area 0.66 0.76 (±0.10) Positive
Mandible Width 0.33 0.36 (±0.05) Isometry
Mandible Height 0.33 0.39 (±0.06) Positive
Research QuestionsIn this study we examined the following questions1. Are the data phylogenetically patterned and how are the results
affected when statistically accounting for phylogeny? 2. Do masticatory scaling patterns differ in males and females? 3. How do scaling patterns differ among platyrrhines, cercopithecoids,
and hominoids?
Materials • Mean species/sex body mass drawn from Smith and Jungers (1997)• Condylar and mandibular measurements from Terhune (2010)
IntroductionPrevious work on the masticatory apparatus (e.g., Bouvier, 1986a,b; Hylander, 1985;Jungers et al., 1995) has demonstrated unique scaling patterns in the temporomandibular joint (TMJ) and mandible of both platyrrhines and cercopithecoids that can be linked to dietary behaviors. For example, folivory and ingestion of large, tough fruits in cercopithecoids (Bouvier, 1986b; Smith et al., 1983) has been demonstrated to be positively correlated with their deeper mandibles and wider condyles. However, these adaptations are not shared by folivorous platyrrhines (Bouvier, 1986a), suggesting a phylogenetic component to the observed variation. Notably, these studies did not take into account the phylogenetic relationships among species, did not include hominoids (and assessed cercopithecines and platyrrhines separately), and only evaluated males or females without consideration of both sexes. Females were initially analyzed separately from males in Bouvier (1986a:553) but were removed when it was concluded that “few statistically significant differences were found between the scaling patterns of the two sexes”. In this study, we analyze a broad sample of anthropoid primates to determine the role of phylogeny and sexual dimorphism in masticatory scaling.
Methods• RMA regressions (Smith, 2009) of condyle and corpus measurements against both
mandible length (as a measure of the masticatory lever arm )and body mass (as an indicator of the overall size of the animal) (i.e., Hylander, 1985; Vinyard, 2008)
• Males and females were analyzed separately; analyses were initially performed on all taxa and then for platyrrhines, cercopithecoids, and hominoids separately
• All data were log transformed for analysis
Literature CitedBouvier M. 1986a. Int J Prim 7: 551-567 Bouvier M. 1986b. AJPA 69 :473-482 Hylander W. 1985. Am Zool25:315-330Smith RJ. 2009. AJPA 140: 476-486Smith J, Jungers W. 1997. JHE 32:523-559 Terhune C. 2010. Ph.D. Diss, ASUVinyard C. 2008. In: Prim Craniofac Func Biol, pp. 357-385.
[email protected]@uark.eduTerhunelab.uark.edu
AcknowledgementsFunding for this research was initially provided by NSF (BCS 0752661) and The Leakey Foundation (grants to CET). Thanks to the American Museum of Natural History, the Department of Primatology at the State Collection of Anthropology and Paleoanatomy, the National Museum of Natural History, the Field Museum, and the Royal Museum for Central Africa for access to their primate collections.
Results• All regressions were significant (p<0.0016)
with r2>0.741 (all taxa) or r2>0.65 (clades separated)
• A strong phylogenetic signal was found for most relationships
• Condylar variables (length, width, area) tend to be positively allometric, whereas mandibular measurements were more likely to scale with isometry
Cercopithecus mitisCercopithecus nictitansErythrocebus patasMiopithecus talapoin
Alouatta belzebulAlouatta palliataAlouatta seniculusAteles geoffroyi
Lagothrix lagotrichaAotus trivirgatusCebus albifrons
Cebus apellaCebus capucinus
Saimiri sciureus
Gorilla beringeiGorilla gorilla gorillaHomo sapiens
Hylobates agilisHylobates klossiiHylobates lar
Pan paniscusPan troglodytes schweinfurthiiPan troglodytes troglodytesPan troglodytes verusPongo abeliiPongo pygmaeus
Symphalangus syndactylus
Cacajao melanocephalusPithecia pithecia
Cercocebus torquatus
Lophocebus albigena
Macaca fascicularisMacaca nemestrina
Mandrillus sphinx
Papio anubisPapio cynocephalusPapio ursinus
Theropithecus gelada
Colobus polykomos
Nasalis larvatus
Piliocolobus badiusProcolobus verus
Semnopithecus entellusTrachypithecus obscurus
Total Species = 44Platyrrhines =12Cercopithecoids = 19 Hominoids = 13
Λ*, Strength of the phylogenetic signal approximated 0-1
Sex X Y All Platy. Cerco. Hom.
Fem
ale
Man
dib
leLe
ngt
h
Condyle Width 0.91 0.00 0.67 0.00Condyle Length 0.86 0.00 0.00 0.00Condyle Area 0.92 0.31 0.42 0.00
Mandible Width 1.00 0.00 0.85 1.00Mandible Height 0.99 1.00 0.00 1.00
Bo
dy
Mas
s
Mandible Length 0.95 1.00 1.00 0.90Condyle Width 0.87 0.92 0.74 0.00Condyle Length 0.87 0.83 0.83 0.63Condyle Area 0.89 0.88 0.76 0.51
Mandible Width 0.96 1.00 1.00 0.56Mandible Height 0.95 1.00 1.00 0.69
Mal
e
Man
dib
leLe
ngt
h
Condyle Width 0.95 0.00 0.71 0.00Condyle Length 0.90 0.00 0.00 0.00Condyle Area 0.95 0.00 0.59 0.00
Mandible Width 0.99 1.00 1.00 1.00Mandible Height 1.00 1.00 0.98 1.00
Bo
dy
Mas
s
Mandible Length 0.92 0.97 0.94 0.00Condyle Width 0.76 0.91 0.70 0.00Condyle Length 0.87 1.00 0.81 0.00Condyle Area 0.86 1.00 0.77 0.00
Mandible Width 0.91 1.00 0.97 0.00Mandible Height 0.92 0.82 0.89 0.43
*a value of 0 signifying no signal, 1 signifying a strong signal
Regression Results When All Taxa are Considered
X YSlope of Isometry RMA Slope Result
Man
dib
le
Len
gth
Condyle Width 1.00 1.20 (±0.13) Positive
Condyle Length 1.00 1.12 (±0.11) Positive
Condyle Area 2.00 2.28 (±0.26) Positive
Mandible Width 1.00 1.10 (±0.14) Isometry
Mandible Height 1.00 1.07 (±0.14) Isometry
Bo
dy
Mas
s
Mandible Length 0.33 0.36 (±0.05) Isometry
Condyle Width 0.33 0.43 (±0.07) Positive
Condyle Length 0.33 0.40 (±0.06) Positive
Condyle Area 0.66 0.81 (±0.13) Positive
Mandible Width 0.33 0.39 (±0.07) Isometry
Mandible Height 0.33 0.38 (±0.07) Isometry
3.5 4.0 4.5 5.0
1.0
1.5
2.0
2.5
Mandible Length
Co
nd
yle
Le
ng
th
3.5 4.0 4.5 5.02
.02
.53
.03
.5
Mandible Length
Condyle
Wid
th
3.5 4.0 4.5 5.0
2.5
3.5
4.5
5.5
Mandible Length
Condyle
Are
a
3.5 4.0 4.5 5.0
1.5
2.0
2.5
3.0
Mandible Length
Mandib
le W
idth
7 8 9 10 11
3.5
4.0
4.5
5.0
Body Mass
Mandib
le L
ength
7 8 9 10 11
2.0
2.5
3.0
3.5
Body Mass
Condyle
Wid
th
7 8 9 10 11
1.0
1.5
2.0
2.5
Body Mass
Co
nd
yle
Len
gth
7 8 9 10 11
2.5
3.5
4.5
5.5
Body Mass
Condyle
Are
a
3.5 4.0 4.5 5.0
2.0
2.5
3.0
3.5
Mandible Length
Condyle
Wid
th
3.5 4.0 4.5 5.0
1.0
1.5
2.0
2.5
Mandible Length
Condyle
Le
ngth
3.5 4.0 4.5 5.0
2.5
3.5
4.5
5.5
Mandible Length
Condyle
Are
a
3.5 4.0 4.5 5.0
1.5
2.0
2.5
3.0
Mandible Length
Mandib
le W
idth
7 8 9 10 11 12
3.5
4.0
4.5
5.0
Body Mass
Mandib
le L
ength
7 8 9 10 11 12
2.0
2.5
3.0
3.5
Body Mass
Condyle
Wid
th
7 8 9 10 11 12
1.0
1.5
2.0
2.5
Body Mass
Condyle
Length
7 8 9 10 11 12
2.5
3.5
4.5
5.5
Body Mass
Condyle
Are
a
Measurements of the mandible utilized by Bouvier(1986a) and employed here.
DiscussionThese results indicate the data are phylogenetically patterned (RQ1), males and females do show different scaling patterns (RQ2), and masticatory scaling patterns vary across clades (RQ3).• Platyrrhine males and females show the same general pattern of isometric scaling
relationships with the exception of a significant positive allometry of condylar area on body mass in females.
• Cercopithecoids demonstrated more variation between males and females than platyrrhines. Notably, in cercopithecoid males mandible width vs. mandible length was negatively allometric while females demonstrated isometry. Males cercopithecoids demonstrated positive allometry in mandible height on body mass.
• Hominoids primarily scale with positive allometry, with strong positive allometry in condylar width, length, and area in females and condylar area in males.
Our results suggest that the previous analysis (Bouvier, 1986a,b), though sufficient at the time, can be improved upon by incorporating phylogenetic methods as well as including hominoids and females. These revised analyses indicate that masticatory scaling patterns vary considerably across sexes and clades, potentially in relation to dietary or other behavioral differences.
Platyrrhini
Cercopithecoidea
Hominoidea
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