ecological filtering and exaptation in the evolution …
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ECOLOGICAL FILTERING AND EXAPTATION IN THE EVOLUTION OF
MARINE SNAKES
William Gearty
@willgearty
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CONVERGENT EVOLUTION IS COMMON
Kelley and Pyenson 2015, Science
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BUT NOT ALWAYS DUE TO ADAPTATION
National Geographic
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National Geographic
Clemente 2014, Evolution
BUT NOT ALWAYS DUE TO ADAPTATION
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National Geographic
Clemente 2014, Evolution
BUT NOT ALWAYS DUE TO ADAPTATION
Other
Bipedal
Posterior Anterior
-0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2Residual Center of Mass
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BUT NOT ALWAYS DUE TO ADAPTATION
AMNH
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BUT NOT ALWAYS DUE TO ADAPTATION
Modified from MacFadden 2005, Science
Increasing aridity and spread of grasslands inNorth America
AMNH
Milli
on o
f yea
rs a
go
Grazers
Mixed Feeders
Browsers
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BUT NOT ALWAYS DUE TO ADAPTATION
9Wiens and Hoverman 2008, Evolution and Development
BUT NOT ALWAYS DUE TO ADAPTATION
10Wiens and Hoverman 2008, Evolution and Development
BUT NOT ALWAYS DUE TO ADAPTATION
Digit Loss
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HOW TO DISCRIMINATEIN DEEP TIME?
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HOW TO DISCRIMINATEIN DEEP TIME?
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Evolution of Trait
Inva
sion
of N
ew N
iche
DISCRIMINATING AMONG MECHANISMS
Modified from Gearty, Carrillo, and Payne 2021, The American Naturalist
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After Invasion
During Invasion
Before Invasion
Evolution of Trait
Inva
sion
of N
ew N
iche
Modified from Gearty, Carrillo, and Payne 2021, The American Naturalist
DISCRIMINATING AMONG MECHANISMS
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After Invasion
Before Invasion
During Invasion
Modified from Gearty, Carrillo, and Payne 2021, The American Naturalist
DISCRIMINATING AMONG MECHANISMS
Evolution of Trait
Inva
sion
of N
ew N
iche
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DISCRIMINATING AMONG MECHANISMS
After Invasion
Before Invasion
During Invasion
Evolution of Trait
Inva
sion
of N
ew N
iche
Modified from Gearty, Carrillo, and Payne 2021, The American Naturalist&
Exa
ptat
ion
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DISCRIMINATING AMONG MECHANISMS
After Invasion
Before Invasion
During Invasion &
Exa
ptat
ion
Evolution of Trait
Inva
sion
of N
ew N
iche
Modified from Gearty, Carrillo, and Payne 2021, The American Naturalist
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EVOLUTION OF MARINE SNAKES
wikipedia.org
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BIOME DATA COLLECTION
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BIOME OCCUPANCY
1243 Total Snake Species
38 17 1592
267
921
691
221
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OTHER DATA
• Body mass
• Average temperature• Average elevation
• Phylogeny (timescaled with fossil calibrations)
• Reproductive mode (eggs vs. live birth)
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ESTIMATE ANCESTRALBIOMES AND TRAITS
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ESTIMATE ANCESTRAL BIOMES
revbayes.github.io
DEC MODEL
29Gearty, Carrillo, and Payne 2021, The American Naturalist
ESTIMATE ANCESTRAL BIOMES
F
W
S
K
File snakes
Water snakes
Sea snakes
Sea kraits
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JOINTLY ESTIMATE OTHER TRAITS AND ENVIRONMENTAL VARIABLES
threshml• Jointly estimates discrete and continuous characters• Threshold model for discrete characters• Infers (and accounts for) covariances of characters
Felsenstein 2005, Proceedings B
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JOINTLY ESTIMATE OTHER TRAITS AND ENVIRONMENTAL VARIABLES
Gearty, Carrillo, and Payne 2021, The American Naturalist
F
W
S
K
File snakes
Water snakes
Sea snakes
Sea kraits
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TRAIT EVOLUTION ACROSS MARINE INVASIONS
After Invasion
Before Invasion
During Invasion &
Exa
ptat
ion
Evolution of Trait
Inva
sion
of N
ew N
iche
Modified from Gearty, Carrillo, and Payne 2021, The American Naturalist
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TRAIT EVOLUTION ACROSS MARINE INVASIONS
After Invasion
Before Invasion
During Invasion &
Exa
ptat
ion
Modified from Gearty, Carrillo, and Payne 2021, The American Naturalist
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ELEVATION
Gearty, Carrillo, and Payne 2021, The American Naturalist
Ecological filtering for lower elevations
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TEMPERATURE
Gearty, Carrillo, and Payne 2021, The American Naturalist
Ecological filtering for warmer temperatures
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No ecological filtering for freshwater history
PREVIOUS AQUATIC HABITATS
Gearty, Carrillo, and Payne 2021, The American Naturalist
No ecological filtering for semiaquatic history
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BODY MASS
Gearty, Carrillo, and Payne 2021, The American Naturalist
Minor ecological filtering?
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VIVIPARITY
Gearty, Carrillo, and Payne 2021, The American Naturalist
Ecological filtering for viviparity
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TAKEAWAYS
• Viviparity may be the most important “preadaptation” to invading the marine realm for snakes
• Strong ecological filtering in all but one invasion lineage
• Previously evolved as an adaptation for climate control during development
• Exapted for preventing suffocation during development
• Marine invasions originated from many different habitats
• Former habitat did not need to be aquatic
• Former habitat must have been in tropical regions at low elevation
• This reduces the need for larger body sizes (although there is still some minor ecological filtering)
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ACKNOWLEDGMENTS
Elsie CarrilloChristianne Orsmby
Jonathan PaynePayne Paleobiology LabLyons Paleoecology Lab
Wagner Paleobiology Lab
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OTHER BIOMES
Gearty, Carrillo, and Payne 2021, The American Naturalist