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Studying complexity of Mesozoic Tethyan food webs to understand
ecosystem restructuringSORMAN, Melanie G.1, DINEEN, Ashley A.2, TYLER, Carrie L.1 and ROOPNARINE, Peter D.2
(1)Department of Geology and Environmental Earth Science, Miami University, Oxford, OH(2)Department of Invertebrate Zoology and Geology, California Academy of Sciences, San Francisco, CA
Normile, 2016
Does Ecosystem Structure Change Through Time?
Dunne et al., 2008 Bush and Bambach, 2011
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Mesozoic Marine Revolution (MMR)
• Abrupt ecosystem reorganization due to increasing predation pressure
• Changes in community structure• Diversification of
predators
• New modes of life
• Greater ecosystem complexity?
Duria Antiquior - Beche
Hypothesis
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• Middle Triassic and Jurassic networks
• Testing effects of increasing predation pressure on marine communities by comparing trophic organization of both networks
• Does ecological complexity increase or change across the MMR?
Tethys
OceanGondwana
Laurasia
Middle Jurassic Scotese, 2001
Integrity of Fossil Food Web StructureModern Caribbean Reef Predicted Fossil Reef
Preserves:
58% of species
66% of genera
42% of guilds
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756 species249 nodes (guilds)Connectance 0.066
441 species163 nodes (guilds)Connectance 0.065
Roopnarine and Dineen, 2018
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Olson & Watters, 2003
Constructing a Food Web
• Step 1: Species List
• Step 2: Ecological Parameterization
• Step 3: Guilds and trophic interactions
• Step 4: Metanetwork
Metrics to Study MMR Structural Changes
Structural Metrics Anisian Bathonian
Species Richness 1185 1363
Guild Richness 105 117
Number of Trophic Links 1006 1000
Linkage Density 9.57 8.55
Connectance 0.0912 0.0731
Number of Trophic Levels 4.88 5.01
Modularity 0.341 0.369
Average Path Length 1.81 1.91
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• Trends characteristic of the MMR• Diversification of predators
• Increased infaunalization
• Larger body sizes
• Increased richness
Functional Diversity
• Species and guild richness increase
• Suggests MMR led to an increase in functional richness
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Structural Metrics Anisian Bathonian
Species Richness 1185 1363
Guild Richness 105 117
Number of Trophic Links 1006 1000
Linkage Density 9.57 8.55
Connectance 0.0912 0.0731
Number of Trophic Levels 4.88 5.01
Modularity 0.341 0.369
Average Path Length 1.81 1.911050
1100
1150
1200
1250
1300
1350
1400
Anisian Bathonian
Tota
l Sp
ecie
s
Species Richness
95
100
105
110
115
120
Anisian Bathonian
Tota
l Gu
ilds
Guild Richness
Trophic Levels• Slight increase in number of trophic levels
• Distribution of trophic levels similar
• Increased suspension feeders in 2nd trophic level• More higher trophic levels (depend on increased primary productivity)
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Structural Metrics Anisian Bathonian
Species Richness 1185 1363
Guild Richness 105 117
Number of Trophic Links 1006 1000
Linkage Density 9.57 8.55
Connectance 0.0912 0.0731
Number of Trophic Levels 4.88 5.01
Modularity 0.341 0.369
Average Path Length 1.81 1.91
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10
20
30
40
50
60
70
1 2 3 4 5
Gu
ild R
ich
nes
s
Trophic Level
Trophic Level Vs. Number of Guilds
Anisian
Bathonian
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Taxa
Pliosaurs, ichthyosaurs, plesiosaurs
Durophagous sharks/rays, cephalopods
Lobsters/crabs, deposit feeders, grazers, benthic carnivores
Suspension feeders, detritivores, microzooplankton
Bacteria, detritus, dinoflagellates, macroalgae
Bathonian Trophic Levels
Trophic Level
1
2
3
4
5
Bottom-up Cascades
11Knoll and Follows, 2016
0
1
2
3
4
5
6
0 5 10 15 20 25 30 35 40 45 50
Tro
ph
ic L
evel
New Guilds
Trophic Levels of New Guilds Present in Bathonian
New Body Size Guilds
New Life Mode Guilds
New Guilds Present in Bathonian• 48 new guilds
• Increased primary producer and predator guilds
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Chemosymbiotic infaunal bivalves, polyplacophora, herbivorous gastropods
Suspension feeders Benthic organisms (carnivorous and omnivorous/grazing gastropods, asteroidean, carnivorous bivalves)
Predators (sharks/rays, chimaeras, sea turtles, cephalopods, fish, eosauropterygia, ichthyosaurs, pliosaurs)
New Life Mode Guilds (N: 15)
Benthic grazing polyplacophora
Benthic herbivorous gastropods
Nektobenthic carnivorous chimaeras
Nektobenthic carnivorous durophagous rays
Boring suspension feeding bivalves
Deposit feeding/grazing sea stars
Mobile infaunal carnivorous bivalves
Hermit crabs
Pliosaurs
Sea turtles
Nektobenthic carnivorous sharks/rays
Nektobenthic carnivorous fast predatory fish
Heteromorph ammonites
Suspension feeding fish
New Body Size Guilds (N: 33)
Chemosymbiotic (Infaunal)(1)
Chemosymbiotic (Infaunal)(3)
Chemosymbiotic (Infaunal)(7)
Suspension Feeder IX Epibiont Epifaunal(2)
Suspension Feeder IX Epibiont Epifaunal(3)
Suspension Feeder IX Epibiont Epifaunal(4)
Suspension Feeder IX Epibiont Epifaunal(5)
Suspension Feeder V Mobile Infaunal(10)
Suspension Feeder V Mobile Infaunal(4)
Suspension Feeder V Mobile Infaunal(5)
Suspension Feeder V Mobile Infaunal(6)
Suspension Feeders III Stationary Epifaunal(13)
Suspension Feeders III Stationary Epifaunal(20)
Suspension Feeders III Stationary Epifaunal(8)
Suspension Feeders III Stationary Epifaunal(9)
Suspension Feeders VII Epibiont SemiInfaunal(1)
Suspension Feeders VII Epibiont SemiInfaunal(2)
Suspension Feeders VII Epibiont SemiInfaunal(5)
Suspension Feeders VII Epibiont SemiInfaunal(60)
Benthic Omnivore/Grazers I(3)
Benthic Omnivore/Grazers I(4)
Benthic Omnivore/Grazers I(5)
Benthic Omnivore/Grazers I(9)
Benthic Carnivores III Epifaunal Gastropods(4)
Benthic Carnivores III Epifaunal Gastropods(9)
Nektonic Carnivores V Ammonites(3)
Nektonic Carnivores III Fast Predatory Fish(4)
Nektonic Carnivores V Ammonites(4)
Nektonic Carnivores V Ammonites(5)
Marine Reptiles II Piercing Predatory Reptiles(11)
Marine Reptiles II Piercing Predatory Reptiles(8)
Marine Reptiles II Piercing Predatory Reptiles(9)
Marine Reptiles III Smash/Crunch Predatory Reptiles(8)
Body Sizes • Larger organisms in Bathonian
• Coincides with radiations of phytoplankton
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0
500
1000
1500
2000
2500
3000
3500
4000
0 10 20 30 40 50
Len
gth
(m
m)
Species Richness
Fish Body Sizes
0
200
400
600
800
1000
1200
0 10 20 30 40 50
Sku
ll Si
ze (
mm
)
Species Richness
Reptile Skull Sizes
Avg: 505 mm
Avg: 246 mm
Leedsichthys out of graph (22000 mm)
Avg: 320 mm
Avg: 1623 mm
0
50
100
150
200
250
300
350
400
450
0 50 100 150 200 250 300
Dia
me
ter
(mm
)
Species Richness
Cephalopod Body Sizes
Avg: 95 mm
Avg: 66 mm
0
200
400
600
800
1000
1200
1400
0 100 200 300 400
Len
gth
(m
m)
Species Richness
Suspension Feeder Body Sizes
Avg: 61 mm Avg: 66 mm
0
20
40
60
80
100
120
140
160
180
200
0 20 40 60 80 100
Len
gth
(m
m)
Species Richness
Deposit Feeders/Grazer Body Sizes
Key
Avg: 26 mm Avg: 43 mm
Modules • Bathonian is partitioned into fewer subcommunities
• Suspension feeders form the largest subcommunity
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BM0
N: 23
BM1N: 61
BM2N: 33
AM3N: 48
AM2N: 32
AM1N: 4
AM0N: 21
63% suspension feeders 72% suspension feeders
Benthic organismsPredatorsBenthic organisms and zooplankton
Predators
MicrozooplanktonBathonianModularity: 0.369
AnisianModularity: 0.341
Infaunal and Epifaunal Life Modes• Increased predation and bioturbation in MMR
• Shift to deeper waters or infaunalization
• Increase in infaunalization in both species and guild richness
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Anisian Bathonian
Total Semi-Infaunal Species 23 23
Number of Semi-Infaunal Guilds 4 6
Total Infaunal Species 73 128
Number of Infaunal Guilds 16 19
Total Epifaunal Species 429 606
Number of Epifaunal Guilds 36 49
0
10
20
30
40
50
60
Semi-Infaunal Infaunal Epifaunal
Gu
ild R
ich
nes
s
Number of Infaunal, Epifaunal, and Semi-Infaunal Guilds
Anisian
Bathonian
Epifaunal Semi-Infaunal
0
100
200
300
400
500
600
700
Semi-Infaunal Infaunal Epifaunal
Spec
ies
Ric
hn
ess
Number of Infaunal, Epifaunal, and Semi-Infaunal Species
Anisian
Bathonian
Len
gth
(m
m)
Anisian
Anisian
Bathonian 9.4%
Bathonian 44.4%
Average Path Length
• Bathonian has longer trophic chains
• More complex and inefficient!
• Makes sense given ecosystem restructuring
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Structural Metrics Anisian Bathonian
Species Richness 1185 1363
Guild Richness 105 117
Number of Trophic Links 1006 1000
Linkage Density 9.57 8.55
Connectance 0.0912 0.0731
Number of Trophic Levels 4.88 5.01
Modularity 0.341 0.369
Average Path Length 1.81 1.91
Conflicting Metrics
• Higher values of linkage density and connectance may lead to increased complexity
• Not supported here
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Structural Metrics Anisian Bathonian
Species Richness 1185 1363
Guild Richness 105 117
Number of Trophic Links 1006 1000
Linkage Density 9.57 8.55
Connectance 0.0912 0.0731
Number of Trophic Levels 4.88 5.01
Modularity 0.341 0.369
Average Path Length 1.81 1.91
Conclusions• MMR: increased predation pressure changes ecosystems
• Anisian to Bathonian: Increase in primary productivity led to increased energy transfer and higher trophic levels
• Triggered ecosystem restructuring and changes in energy transfer pathways, facilitated by radiation of phytoplankton
• Ecosystem structure has changed
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Acknowledgments• Dr. Carrie Tyler, research advisor and committee member
• Dr. Peter Roopnarine, California Academy of Sciences (CAS) collaborator and committee member
• Ashley Dineen, CAS collaborator
• Dr. Hailiang Dong, committee member
• Hannah Goggin, undergraduate research partner
• Joe Tawil, undergraduate research partner
• Ian Castro, research partner
• Hannah Kempf, research partner
• Lyndsey Farrar, research partner
• Paleobiology Database
• Funding sources
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EAR SGP 1629786EAR SGP 1629776
Questions?
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