tsd in reptiles
DESCRIPTION
TSD in Reptiles. Modes, mechanisms and evolution. Arthur Georges Applied Ecology Research Group. Sex determination in lizards. Pough et al: Herpetology 1998. Fundamentally Different?. Genetic sex determination (GSD): Sex determined by genetic factors independent of environment - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/1.jpg)
TSD in Reptiles
Modes, mechanisms and
evolution.
Arthur Georges
Applied Ecology Research Group
![Page 2: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/2.jpg)
Sex determination in lizards
Pough et al: Herpetology 1998
![Page 3: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/3.jpg)
Fundamentally Different?
• Genetic sex determination (GSD): Sex determined by genetic factors independent of environment
• Environmental sex determination (ESD/TSD): Sex determined after fertilisation by environmental factors
![Page 4: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/4.jpg)
Outline
• Overview of modes of action of TSD in reptiles
• Dichotomy or Continuum?
• Predisposition for TSD?
• Overview our work, linking to the more specific talk by Tariq Ezaz
TSD
TSD G SD
G SD
![Page 5: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/5.jpg)
![Page 6: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/6.jpg)
Young Georges Doody Canadian J. Zool, in press
Pig-nosed Turtle
1.0C
![Page 7: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/7.jpg)
Georges Stoutjesdijk Limpus J. Experimental Zool. 1994
4.5C
Loggerhead
![Page 8: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/8.jpg)
Water Dragon Harlow 2001, unpubl. thesis
![Page 9: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/9.jpg)
One Pattern?
After Pieau, 1996
![Page 10: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/10.jpg)
Middle Third of Incubation is
InfluentialYoung Georges Doody Canadian J. Zool. in press
![Page 11: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/11.jpg)
Both Magnitude and variability are important
Mean 26C(Male)
Georges Stoutjesdijk Limpus J. Experimental Zool. 1994
![Page 12: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/12.jpg)
Fundamentally Different?
• Remarkable conservatism of vertebrate sexual differentiation genes, including reptiles with TSD.
• Taxonomic distribution of TSD and GSD species suggests both modes have evolved independently multiple times.
~
Evolutionary transitions between the two mechanisms may be relatively simple, perhaps involving one or only a few genes
Sarre Georges Quinn Bioessays 2004
![Page 13: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/13.jpg)
Top Sex Determining Gene
or Gene Complex
WNT4 (?)
DAX1 (?)
WT1 SF1
Aromatasegene
AMH
SOX9
DMRT1
AromataseAndrostenedione
Testosterone
Estrone
Estradiol 17B Receptors
-
-
-
+
++
Sarre Georges Quinn Bioessays 2004
![Page 14: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/14.jpg)
A. Mutually exclusive mechanisms of sex determination
B. Intermediate forms with varying degrees of interaction
A BTSD
TSD G SD
G SD
Dichotomy or Continuum?
![Page 15: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/15.jpg)
Zaborski et al. 1988 Differentiation
Gonad Blood
HY+ HY- HY+ HY-
MALE 100% 50% 50%
H-Y antigen expression(25-26C)
![Page 16: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/16.jpg)
Gonad Blood
HY+ HY- HY+ HY-
FEMALE 100% 50% 50%
H-Y antigen expression(30-30.5C)
Zaborski et al. 1988 Differentiation
![Page 17: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/17.jpg)
Blood
HY+ HY-
MALE 0 22
FEMALE 42 6
H-Y antigen expression(at the Pivotal Temp)
Zaborski et al. 1988 Differentiation
![Page 18: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/18.jpg)
Girondot Zaborski et al. 1994 Genetical Research
Blood
HY+ HY-
MALE 3 24
FEMALE 106 7
H-Y antigen expression(in the field)
![Page 19: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/19.jpg)
Temperature (deg C)
ProportionMALE
Bassianaduperreyi
Shine Elphick Donnellan 2002 Ecology Letters
![Page 20: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/20.jpg)
Temperature Males Females
34 17 47
32 14 14
30 15 15
28 30 26
26 13 17
24 14 10
22 20 15
Bearded Dragon
Present study
![Page 21: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/21.jpg)
Dichotomy or Continuum?
• Extraordinary conservatism in the genes involved in sexual differentiation across vertebrates
• Abundant examples in fish of co-existence of genetic and environmental influences
• Evidence of co-occurrence of genetic and environmental influences in at least some reptiles
• Relative ease by which species appear to have moved from one mode to the other in evolutionary history
![Page 22: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/22.jpg)
Sister TaxaA.muricatus
A.norrisi
![Page 23: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/23.jpg)
Coincidence?
Homeotherms Ectotherms Poikilotherms
Strictly
GSD
TSD
Common
TSD
Rare
![Page 24: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/24.jpg)
Top Sex Determining Gene
or Gene Complex
SexDifferentiation
Genes
Hormonal
Environment
Range of temperatures experienced up to 23C
(22 – 45C)
![Page 25: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/25.jpg)
Top Sex Determining Gene
or Gene Complex
SexDifferentiation
Genes
Hormonal
Environment
Network of genes and gene products
Thermal Compensation
Consistent signal
TSD
![Page 26: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/26.jpg)
Challenging Opportunities for the Future
Reptiles provide tractable opportunities for studying
vertebrate sex determination through the provision of eggs for study before sex is determined, and provision of numerous examples of GSD/TSD models for study.
Viewing GSD and TSD as discrete and fundamentally different processes is overly myopic and distracts us from the possibility that genotypic and environmental influences may interact in determining sexual phenotypes.
![Page 27: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/27.jpg)
Challenging Opportunities for the Future
Comparative approaches, where closely related
species with differing modes of sex determination are selected, show great promise.
Reptiles may well be predisposed to TSD. We aught to be looking for evidence of temperature compensation in the expression of sex genes in GSD species to provide insight into where to look for changes accompanying the move to and from TSD.
![Page 28: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/28.jpg)
The Team
Applied Ecology Research Group Dr Stephen SarreAlex QuinnBrett LidburySean DoodyEnzo Guarino
Comparative Genomics Group
Australian National University
Prof Jenny Graves
Dr Frank Gruetzner
Dr Ann Gaeth
Dr Tariq Ezaz
Funding
ARC Discovery Grants 1996, 2003, 2004-6UC Research Grant 2002CRC for Freshwater Ecology
Collaborators
Hofstra University, USA
Dr Russell Burke
University of Sydney
Prof. Rick Shine
Contributors
![Page 29: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/29.jpg)
![Page 30: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/30.jpg)
Differential Advantage
When environmental conditions favour fitness of one sex over the other, and when information on which sex is to be favoured is not available at the time of nesting, the decision on sex is deferred.
• Temperature during incubation confers differential advantage, directly or indirectly.
• TSD defers the decision until information on the direction of that advantage is available.
![Page 31: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/31.jpg)
Crews: Evolution and Development 2003
![Page 32: TSD in Reptiles](https://reader036.vdocuments.net/reader036/viewer/2022081501/568152d9550346895dc0f4e7/html5/thumbnails/32.jpg)
Top Sex Determining Gene
or Gene Complex
SexDifferentiation
Genes
Hormonal
Environment
• Networks not “linear” sequences of gene action
• Redundancy in function• Complex system of thermal compensation
Temperature