6/8/2019
1
The Problem with Giants
wild
fact
.com
Livyatan melvillei
2
Gigantism – Giants Defined
• Largest species in an ecological community
• Largest species in an ecological guild
• Largest species in a clade
skyw
alke
r.co
chis
e.ed
u
3
Nonrandom Distribution of Giants
• Cope’s Rule – within a lineage, body size increases through time
4
Nonrandom Distribution of Giants
• Gigantism through timeV
erm
eij (
2016
)
6/8/2019
2
5
Evolution of Large Size
• Large size must have advantages• Relatively lower food requirements
• Obtain a higher proportion of available resources
• Lower locomotion costs (b = -0.2 to -0.4)
• Less vulnerable to predators
mfood = mbody3/4
i.telegraph.co.uk
• Transport in directed systems
6
Supply-Demand Dynamics
B = m3/4
B = (m(rs/rd))D/(D+1)metabolic
rate
supply rate demand rate
dimension
mass
Which simplifies to…
Banavar, et al., 2002
7
Supply-Demand Dynamics
equa
tion-
of-t
he-m
onth
.blo
gspo
t.co
m
b = 0.73
8
Supply-Demand Dynamics
• Scaling of heart rate with heart mass M
achi
da a
nd A
ohag
i (20
01)
6/8/2019
3
9
Types of Allometric Scaling
• Structural scaling(b ~ ⅓ multiples) –based on A-V processes
• Metabolic scaling(b ~ ¾) – based on fractal processes
• Frequency scaling(b ~ -¼) – based on fractal processes
••• • ••
www.buriedtreasurefossils.com
•
= nutrient foramen
•• Pagel’s ‘everyanimal’
• Using present to reconstruct past – constrains past to be like present
• Overreliance on lines of best fit produces ‘average’ animals
• Sequential extrapolations compound averaging in reconstructions
10
Through a Glass, Darkly
ww
w.e
dge.
org
• Size-related changes in scaling• Running speed in quadrupedal mammals
11
Through a Glass, Darkly
Iria
rte-
Día
z(2
002)
cursorial
non-cursorial
30 kg
• Size-related changes in scaling• Swimming speed in bony fishes (□) & cetaceans (▲)
12
Through a Glass, DarklyIr
iart
e-D
íaz
(200
2)
6/8/2019
4
• Size-related changes in behavior• Acceleration in bony fishes (□) & cetaceans (▲)
13
Through a Glass, Darkly
Iria
rte-
Día
z(2
002)
14
Through a Glass, Darkly
15
Upper Limits on Size
• Factors affecting maximum size1. Skeletal support & locomotion
2. Metabolism & thermoregulation
3. Feeding mode & trophic level
4. Environment
www.unexplained
‐mysteries.com
16
1. Skeletal Support & Locomotion
• Skeletal mass must increase faster than body mass• Positive
allometry for bone diameter
Sch
mid
t-N
iels
en (1
984) b = 1.13
6/8/2019
5
2. Metabolism & Thermoregulation
• Thermal strategies• Endotherms (red area)
• Heterotherms/Mesotherms (gray area)
• Ectotherms (green area)
17Ferrón et al. (2017) 18
3. Feeding Mode & Trophic Level
• General trend – animal body size increases at higher trophic levels• Needed to subdue prey
• BUT… are largest animals always top carnivores?• Prey become rarer &
less predictable at higher trophic levels –requires movement over longer distances
19
3. Feeding Mode & Trophic Level
• Giant animals should occur where prey are abundant & incapable of escaping
redm
ehra
pens
min
.blo
gspo
t.co
m
en.wikipedia.org
4. Environment – Aquatic
• Filter-feeders are largest marine animals –carnivores consistently smaller
• Thermal constraints at largest sizes?
• Role of productivity
20carnivoraforum.com
www.north-slope.org
6/8/2019
6
21
4. Environment – Land (Herbivores)
Ullm
ann
et a
l. (2
017)
Hen
ders
on (
2013
)
en
.wik
ipe
dia
.org
22
4. Environment – Land (Carnivores)
en
.wik
ipe
dia
.org
Gar
land
(19
83)
23
4. Environment – Aerial
Sato, et al. (2009)
en.w
ikip
edia
.org
• Scaling relationships = models for expected changes in shape as size increases
• Intrinsic factors • Skeletal support
& locomotion
• Metabolism & thermoregulation
• Feeding mode & trophic level
• Extrinsic factors• Environment &
productivity24
Summary
iliketowastemytime.com
Titanoboa