tsd in reptiles how the physical and the physiological conspire to defeat global warming
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TSD in Reptiles How the physical and the physiological conspire to defeat global warming. Arthur Georges Applied Ecology Research Group University of Canberra. Sex versus Temperature. Established Results. Dramatic effect – usually 100% of one sex or the other - PowerPoint PPT PresentationTRANSCRIPT
TSD in Reptiles
How the physical andthe physiological conspireto defeat global warming
Arthur Georges
Applied Ecology Research GroupUniversity of Canberra
Sex versus Temperature
Established Results
Dramatic effect – usually 100% of one sex or the other
Only a small range of temperatures (threshold) produces both sexes
TSD is widespread among reptiles
European Pond Turtle (France)
NESTMEANTEMP
RANGEEXPSEX
OBSSEX
I 24.8 7.5 male female
II 23.9 6.0 male male
III 26.8 5.9 male female
IV 25.8 5.7 male female
V 25.5 5.0 male female
Threshold = 28°C
Temperatures in Natural Nests
Temperaturesrecorded atfour depthsover 24hrs
American Map Turtles
Diel Cycle
Daily Temperature
Cycle
T = R Cos (t) + M
where M is the meanand +/-R is the range
Diel Cycle
Daily Temperature
Cycle
T = R Cos (t) + M
where M is the meanand +/-R is the range
Diel Cycle
Diel Cycle
Linear CTE Model
CTE = R.Cos (t’) + M
t’ = - sin (t’) R
2 M – T0
Predicting Sex
American Map Turtles
Development Rate
Development Rate
increases linearly with time
= A(T – T0)
where T0 is thedevelopmental zero
ds
dt
Sex vs Temperature
Sex ratios versusDaily range
At a fixed mean of 26°C
Line = model prediction
Loggerhead Turtles
Loggerhead Turtles
Sex ratios versusDaily range
At a fixed mean of 26°C
Line = model prediction
Daily Thermal Regimes
Mean temperaturevaries a little –
by 0.6°C
Daily range variesby up to 3.0 °C
CTE variesby about 2.0 °C
Thermal Gradients
Development in Carettochelys
Core Temperature Trace
Core Temperature Trace
Core Temperature Trace
Linear Model
Fitting Non-linear Models
Sharpe-DeMichelle Model
Incubation Period
Sex
Sex
Conclusion
Contrary to previous reports…
Conclusion
Global warming may well NOT be the female turtle’s answer to male chauvinism!
Single Switch
Title?
Patterns of oxygen
consumption during incubation
Linear CTE Model – example
Emys orbicularis – France (Pieau, 1982)
T0 = 16.1, Mean = 24.8°C, R = 7.5 °C
t’ = 0.8980 (6 hrs 51 mins) after 14 iterations
CTE = 29.5 °C
CTE = R.Cos (t’) + M
t’ = - sin (t’) R
2 M – T0
Refinement #1
When temperatures drop below the developmental zero each day
Yet to be done…
Test the utility of the models in real field situations
Test the Linear CTE Model with Threshold in the laboratory, incorporate the Sharpe-DeMichelle Model
Simplify computation – the WEB
Explore the broader implications for hatchling phenotypes in general
Global warming
Double Switch
European Pond Turtle (France)
NESTMEANTEMP
RANGE CTEEXPSEX
OBSSEX
I 24.8 7.5 29.5 female female
II 23.9 6.0 27.4 male male
III 26.8 5.9 29.6 female female
IV 25.8 5.7 28.6 both female
V 25.5 5.0 27.8 male female
Threshold = 28°C
Sex versus Temperature