Tooth wear - causes and (evolutionary) consequences

review of the evidence

Thomas Kaiser, Ellen Schulz Zoological Museum, University of Hamburg, Germany

Jürgen Hummel Animal Nutrition Group, University of Bonn, Germany

Dennis Müller, Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife, University of Zurich, Switzerland

NESCent Symposium 2011

Tooth wear

•!Do animals show adaptations to tooth wear?

•!Do variations in tooth wear drive the quantitative expression of these adaptations?

•!Hypsodonty, mesowear, tooth wear (height/volume per time)

•!Diet abrasiveness

Hypsodonty and grass

own evaluation, but similar findings published by Janis (1995), Perez-Barberia and Gordon (2001), Mendoza and Palmqvist (2008)

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1

Pro

port

ion e

xcessiv

e w

ear

fed from dishes/racks

fed on sandy soil

from Healey et al. (1965)

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0 50 100 150 200 250

Soil ingestion (g/d)

Incis

or

length

(in

.)

Soil ingestion and wear

from Healey et al. (1966)

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45

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Month

Wear

in p

recedin

g 6

weeks

(in.)

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0.01

0.02

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0.08

Faecal s

oil (%

DM

)

Faecal soil (%DM)

Wear

Soil ingestion and wear

Foto: Johanna Castell

method developed by Fortelius, Solounias (Kaiser)

=0

=1

=2

=3

=4

Free-ranging vs. captive giraffes

from Clauss et al. (2007)

from Clauss et al. (i2007)

-1.50

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

Diffe

rence in s

core

Less abrasion than in the wild

More abrasion than in the wild

-1.5

-1

-0.5

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0.5

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1.5

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2.5

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0 1 2 3 4 5 6

Hypsodonty index

Diffe

rence in s

core

BR

IM

GR

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20

40

60

80

100

120

140

160

180

0 20 40 60 80 100

%grass

Faecal silic

a (

mg/k

g D

M)

dry season

wet season

R2 = 0.66

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7

8

9

10

0 50 100 150

Faecal silica (mg/kg DM)

Hypsodonty index

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5

6

0 1 2 3 4 5

Annual wear rate (mm)

Hypsodonty

index

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0 1 2 3 4 5

Annual wear rate (mm)

Hypsodonty

index

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5

6

0 1 2 3 4 5

Annual wear rate (mm)

Hypsodonty

index

Testing the mesowear signal

•!Species level (comparative) •!Calculating mesowear score from Fortelius & Solounias (2000) and the data collection of Kaiser; matching hypsodonty index from Janis (1988)

•!Using %grass from own data collection •!Using habitat score from Mendoza & Palmqvist (2008)

•!Using precipitation and other climate data from Pantheria

•!Analyses with OLS and PGLS

R2 = 0.66

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1

2

3

4

5

6

7

0 50 100 150

Faecal silica (mg/kg DM)

Hypsodonty index

Mesowear score

Is diet abrasiveness reflected in the mesowear score?

R2 = 0.66

0

1

2

3

4

5

6

7

0 50 100 150

Faecal silica (mg/kg DM)

Hypsodonty index

Mesowear score

Is diet abrasiveness reflected in the mesowear score?

R2 = 0.66

R2 = 0.35

0

1

2

3

4

5

6

7

0 50 100 150

Faecal silica (mg/kg DM)

Hypsodonty index

Mesowear score

Is diet abrasiveness reflected in the mesowear score?

Is diet abrasiveness reflected in the mesowear score?

R2 = 0.66

R2 = 0.35

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1

2

3

4

5

6

7

0 50 100 150

Faecal silica (mg/kg DM)

Hypsodonty index

Mesowear score

R2 = 0.40

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1

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8

9

10

0 20 40 60 80 100

%grass

Hypsodonty index

Mesowear score

Mesowear score, diet and habitat

R2 = 0.38

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1

2

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6

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8

9

10

0 1 2 3 4

Habitat category

Hypsodonty index

Mesowear score

R2 = 0.40

0

1

2

3

4

5

6

7

8

9

10

0 20 40 60 80 100

%grass

Hypsodonty index

Mesowear score

Mesowear score, diet and habitat

R2 = 0.38

0

1

2

3

4

5

6

7

8

9

10

0 1 2 3 4

Habitat category

Hypsodonty index

Mesowear score

20 40 60 80 100

%grass

R = 0.38

0

1

2

3

4

0 1 2 3

Habitat category

0

1

2

3

4

5

6

7

8

9

10

0 20 40 60 80 100

%grass

Hypsodonty

index

open

medium

closed

This shows that both %grass and habitat influence HI

R2 = 0.40

0

1

2

3

4

5

6

7

8

9

10

0 20 40 60 80 100

%grass

Hypsodonty index

Mesowear score

Mesowear score, diet and habitat

R2 = 0.38

0

1

2

3

4

5

6

7

8

9

10

0 1 2 3 4

Habitat category

Hypsodonty index

Mesowear score

R2 = 0.40

R2 = 0.32

0

1

2

3

4

5

6

7

8

9

10

0 20 40 60 80 100

%grass

Hypsodonty index

Mesowear score

Mesowear score, diet and habitat

R2 = 0.38

0

1

2

3

4

5

6

7

8

9

10

0 1 2 3 4

Habitat category

Hypsodonty index

Mesowear score

R2 = 0.40

R2 = 0.32

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1

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3

4

5

6

7

8

9

10

0 20 40 60 80 100

%grass

Hypsodonty index

Mesowear score

Mesowear score, diet and habitat

R2 = 0.38

R2 = 0.130

1

2

3

4

5

6

7

8

9

10

0 1 2 3 4

Habitat category

Hypsodonty index

Mesowear score

R2 = 0.40

R2 = 0.32

0

1

2

3

4

5

6

7

8

9

10

0 20 40 60 80 100

%grass

Hypsodonty index

Mesowear score

Mesowear score, diet and habitat

R2 = 0.38

R2 = 0.130

1

2

3

4

5

6

7

8

9

10

0 1 2 3 4

Habitat category

Hypsodonty index

Mesowear score

R2 = 0.32

20 40 60 80 100

%grass

R = 0.38

R2 = 0.130

1

2

3

4

0 1 2 3

Habitat category

0

0.5

1

1.5

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2.5

3

3.5

4

0 20 40 60 80 100

%grass

MesowearScore

open

medium

closed

This shows that the mesowear signal is not catching a habitat effect

R2 = 0.40

R2 = 0.32

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0 20 40 60 80 100

%grass

Hypsodonty index

Mesowear score

Mesowear score, diet and habitat

R2 = 0.38

R2 = 0.130

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2

3

4

5

6

7

8

9

10

0 1 2 3 4

Habitat category

Hypsodonty index

Mesowear score

R2 = 0.15

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0 50 100 150 200 250

Precipitation (mm)

Hypsodonty index

Mesowear score

R2 = 0.13

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8

9

10

0 500 1000 1500 2000

Evaporation (mm)

Hypsodonty index

Mesowear score

R2 = 0.40

R2 = 0.32

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0 20 40 60 80 100

%grass

Hypsodonty index

Mesowear score

Mesowear score, diet and habitat

R2 = 0.38

R2 = 0.130

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2

3

4

5

6

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8

9

10

0 1 2 3 4

Habitat category

Hypsodonty index

Mesowear score

R2 = 0.15

R2 = 0.050

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2

3

4

5

6

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8

9

10

0 50 100 150 200 250

Precipitation (mm)

Hypsodonty index

Mesowear score

R2 = 0.13

R2 = 0.04

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0 500 1000 1500 2000

Evaporation (mm)

Hypsodonty index

Mesowear score

Mesowear score and body mass

R2 = 0.10

0.01

0.1

1

10

1 10 100 1000 10000

Body mass (kg)

Hypsodonty index

Mesowear score

not significant after phylogenetic control

Mesowear score and body mass

R2 = 0.10

R2 = 0.00

0.01

0.1

1

10

1 10 100 1000 10000

Body mass (kg)

Hypsodonty index

Mesowear score

Does tooth wear drive the evolution of hypsodonty?

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1

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0 1 2 3 4

Mesowear score

Hypsodonty

index

Does tooth wear drive the evolution of hypsodonty?

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0 1 2 3 4

Mesowear score

Hypsodonty

index

10-100 kg

100-1600 kg

Influence of body mass not significant with phylogenetic control

Does tooth wear drive the evolution of hypsodonty?

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Mesowear score

Hypsodonty

index

Ruminants CamelidsEquids RhinosHyraxes

Does tooth wear drive the evolution of hypsodonty?

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0 1 2 3 4

Mesowear score

Hypsodonty

index

Tragulids

Giraffids

Cervids

Bovids

Antilocapra

Does tooth wear drive the evolution of hypsodonty?

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0 1 2 3 4

Mesowear score

Hypsodonty

index

Bovinae AlcelaphinaeAepyceroidae HippotraginaeReduncinae CephalophinaeSaiginae AntilopinaeCaprinae

Does tooth wear drive the evolution of hypsodonty?

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0 1 2 3 4

Mesowear score

Hypsodonty

index

open

medium

closed

This shows that both mesowear and habitat influence HI - again showing that there is something in habitat that the mesowear score does not catch

Predicting %grass / precipitation

For predicting %grass, in a GLM both HI and MesowearScore are significant; body mass only when not correcting for phylogeny.

LS LogBM HI Mesoscore r2 p p p OLS (F) 8.424 0.005 (F) 16.192

Predicting %grass / precipitation

For predicting %grass, in a GLM both HI and MesowearScore are significant; body mass only when not correcting for phylogeny.

LS LogBM HI Mesoscore r2 p p p OLS (F) 8.424 0.005 (F) 16.192

Predicting %grass / precipitation

For predicting %grass, in a GLM both HI and MesowearScore are significant; body mass only when not correcting for phylogeny.

LS LogBM HI Mesoscore r2 p p p OLS (F) 8.424 0.005 (F) 16.192

Predicting %grass / precipitation

For predicting %grass, in a GLM both HI and MesowearScore are significant; body mass only when not correcting for phylogeny.

LS LogBM HI Mesoscore r2 p p p OLS (F) 8.424 0.005 (F) 16.192

common taxa rare taxa

Crown types Localities

Relationship HI - enamel ridge alignment?

Relationship HI - enamel ridge alignment?

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0 1 2 3 4 5 6

HI

Fre

quency (

10-4

0°)

Relationship HI - enamel ridge alignment?

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0 1 2 3 4 5 6

HI

Fre

quency (

10-4

0°)

n.s.

No link between HI and enamel ridge alignment - no realtionship between HI and one quantitative tooth shape parameter we have

Relationship HI - enamel ridge alignment?

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40

45

0 1 2 3 4 5 6

HI

Fre

quency (

10-4

0°)

n.s.

Enamel ridge alignment and hypsodonty are two independent adaptations

Some brachydont teeth do good things ...

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4.5

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free-ranging captive

MPS (

mm

)

Przewalski

Tapir

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3.5

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4.5

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free-ranging captive

MPS (

mm

)

Przewalski

Tapir

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1.2

free-ranging captive

MPS (

mm

)

Aurochs

Giraffe

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0.2

0.4

0.6

0.8

1

1.2

free-ranging captive

MPS (

mm

)

Aurochs

Giraffe

Silica (%DM)

Summary

•!Hypsodonty can most logically be explained as a adaptation to tooth wear

•!Abrasiveness of diet is mostly a concept and not an empirical measure

•!Differences in wear can be demonstrated under different situations

•!Important differences in the signal of hypsodonty (evolutionary) and mesowear (individual’s lifetime)

•!Quantitative effects of diet on tooth wear are needed

Summary

The mesowear score as in our collection does not relfect climate/habitat to the same extent as HI. HI is an evolutionary signal. MesoScore is a signal from an individual animal that may be exposed to different conditions than the animal was during its evolution of HI.

This does not mean that at lower-scale comparisons (e.g. within one group of herbivores only) the MesoScore is more linked to climate parameters.