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Turtles: a cause for wonder, a cause for concern. Thomas Akre Longwood University Farmville, VA. The Tortoise and the Hare. Turtles: a cause for wonder. - PowerPoint PPT Presentation
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Turtles: a cause for wonder, a cause for concern
Thomas AkreLongwood University
Farmville, VA
The Tortoise and the Hare
Turtles: a cause for wonder
• "Because they are still living, turtles are commonplace objects to us: were they entirely extinct, their shells – the most remarkable defensive armor ever assumed by a tetrapod – would be a cause for wonder."
Alfred Sherwood Romer (1894–1973)
Remarkable Defensive Armor
E. S. Gaffney.
Survivors in Armor• Turtles (Order Testudines) are a unique
(monophyletic) and highly divergent lineage
• They have existed nearly unchanged for at least 210 million years and survived the last great mass extinction 65 mya
Survivors in Armor
Millions of years ago Thousands of Genera
All GeneraWell-defined Genera
Mass Extinctions
Triassic
Survivors in Armor
Survivors in Armor
Millions of years ago Thousands of Genera
All GeneraWell-defined Genera
Mass ExtinctionsCretaceous “K-T”
Survivors in Armor
Turtles in the Tree of Life
Laurin & Gauthier 2009
Turtle Relatives - Procolophonids
Nycteroleter
D. Bogdanov
Turtle Relatives - Pareiasaurs
E. Karkemish
Turtles in the Tree of Life
Modesto & Anderson 2004
Turtle Relatives - Plesiosaurs
Thalassiodracon hawkinsi
N. Tamura
The First Turtle?
Li et al. 2008
Odontochelys semitestacea
M. Donnelly
The Earliest Turtles
Li et al. 2008C. Houck
Proganochelys quenstedti
The Turtle Tree of Life
Joyce & Gauthier 2004
Odontochelys
Tortoise and Freshwater Turtle Species Richness by 12100 km2 Grid
Species Richness
The Side-Neck Turtles
Gaffney and Meylan 1988
How to Protect Your Neck
PleurodireF. Ippolito.
Cryptodire
The Side-Neck Turtles• Pleurodires
Tortoise and Freshwater Turtle Mean Root Distance by 12100 km2 Grid
Global Diversification
Renous et al. 2008
Meiolania: the Horned Turtle
Gaffney and Meylan 1988
Meiolania: Survivors in ArmorMeiolania platyceps
C. Houck
F. Ippolito.
Oceanic Voyages
Gerlach et al. 2006
So what is a turtle and what does it mean to be a turtle?
• In general, turtles have a suite of co-evolved life history characteristics that make them vulnerable to the effects of human encroachment
• Life history theory and evidence from long-term population studies suggest that turtles live so long because they are bet-hedgers; they have adapted to environments with unpredictable juvenile survivorship
General Model of Turtle Life-History Traits
• Low nest (clutch) survivorship• Low, but variable juvenile survivorship• Delayed sexual maturity (4–30 yrs)• At a certain size the shell confers protection that
leads to high adult survivorship (often > 95%) • Low annual reproductive output (fecundity)• Repeated reproductive cycles (extreme iteroparity)• Long life-span (mean max. from 15–200 yrs)• Reduced or non-existent senescence
Delayed Maturity
A. Teti
Glyptemys muhlenbergii
Loxodonta africana
The Whale in the TurtleDermochelys coriacea
C. Safina
“Mammalian” Bone Growth
Wyneken et al. 2008
Giant Turtles
R. Somma
Stupendemys geographicus
F. A. Lucas
Archelon ischryos
Survival
The Tongue of the Turtle
Heiss et al. 2010
The Fish in the Turtle
Feeding
A Buffer Against the Cold
Temperature Dependent Sex Determination and Female Choice
Chrysemys picta
M. JonesM. Marchand
Nest Site Selection & DiapauseCann 1998
Diapause and Aestivation
Longevity
Reproduction & Longevity• Indeterminant Growth and Experience
Reproductive output,Nest Success &
Hatchling survivorship
Cost of reproduction
Turtles: a cause for concern
• "Because they are still living, turtles are commonplace objects to us: were they entirely extinct, their shells – the most remarkable defensive armor ever assumed by a tetrapod – would be a cause for wonder."
Alfred Sherwood Romer (1894–1973)
There is a
Global Turtle Survival Crisis
Habitat Loss
Unsustainable Use
Disease
Global Turtle Survival Crisis
Invasive species
Global Climate Change Pollution
Primary feeder markets of
turtleimports into
China……have now reached into India, New
Guinea, Africa, and the United
States
IUCN RED LIST CATEGORY STATUS FOR THE WORLDS 265+ TURTLES
23
48
6242
12
74
22
ExtinctExtinct in WildCritically EndangeredEndangeredVulnerableLower RiskData DeficientNot Evaluated
Nearly half (42%) of the world’s tortoise and freshwater turtle species are threatened with
extinction
At least 70 species (± 25%) are poised on the brink of extinction
Discoveries, rediscoveries, and elevations
Discoveries, rediscoveries, and elevations
Turtle Services• They occupy a diverse array of ecological
niches and many species are considered to be critical components of the ecosystems they inhabit
M. Dorcas D. Scott
Turtle Symbols
Global Species Richness and Turtle Hotspots
Tortoise and Freshwater Turtle Species Richness by 12100 km2 Grid
Turtle Hotspots and Priority Areas
Ganges-Brahmaputra Basin of India and Bangladesh
The Human Footprint
58 species of five families in North America
Turtle Priority Areas
The Tortoise and the Hare
Thank you