Prior research the North American turtle species, Chelydra serpentina (North American Snapping Turtle), has produced an unanticipated observation. There is low variability in the normally hypervariable displacement loop (d-loop) of the control region (CR) mitochondrial (mt)DNA. Paleoclimatic data was used to qualitatively investigate the causes for the lack of genetic variation observed in C. serpentina. For comparison, similar investigations were made on the ranges of two understudied related species, Chelydra rossignonii (Mexican Snapping Turtle) and Chelydra acutirostris (South American Snapping Turtle). A series of Pleistocene bottlenecks caused by a southward climatic shift in the 18˚C mean July temperature (apparently needed for egg incubation) and lethal marine transgressions over the Florida Peninsula related to interglacial transitions offer an explanation for the low genetic diversity of CR mtDNA found among C. serpentina populations. In contrast, the two Central and South American species both have Pleistocene glacial-interglacial refugia embedded within significant portions of their ranges. These climatically stable regions isolated the two species and promoted genetic divergence. Video of presentation by Jack Corbo on my facebook page (www.facebook.com/jack.corbo.9)

1. An Overview of the Paleoclimatic
Influences on the Genetic Variation of Chelydra
by
Jack M. Corbo and H. Greg McDonald
Bulletin of the Chicago Herpetological Society, June/July 2016

2. “We must expect a compromise between the human need for pigeon-holing
facts and the variety and fluidity of nature.” –J.S. Huxley

3. Chelonian Lineage Unclear

4. Odontochelys semitestacea

5. Ancestral Chelonians

6. Clypemys insculpta Maze Learning
(N.A. Wood Turtle)

7. PETM and Origins of Protochelydra

8. Protochelydra zangerli
56 Ma, Alaska

9. Protochelydra Comparison

10. Ohio Hopewell Culture (100BC-AD400)
Snapping Turtle Platform Pipe

11. 1900’s Seneca Vessel Rattle
(kanyáhte’ ká’owá)

12. 1808 American Political Cartoon of
Jefferson Embargo Act

13. Children’s Literature

14. Scientific Literature

15. Chelydra Art
(Marty Capron)

16. Reluctant Model
Herps Alive Foundation

17. Road Mortality
Anthropogenic Interactions

18. Non Lethal
Anthropogenic Interactions

19. Anthropogenic Effects
(faux bicephalic C. serpentina)

20. Non Lethal
Anthropogenic Effects

21. Taxonomy

22. Taxonomy of the Family
Chelydridae
Macrochelys
M. temminckii
M. suwanniensis
M. apachicolae
Chelydra
C. serpentina
C. rossignonii
C. acutirostris

23. Macrochelys temminckii
(Alligator Snapping Turtle)

24. Chelydra serpentina
(North American Snapping Turtle)

25. Chelydra and Macrochelys

26. C. Serpentina
Skeletal Features

27. Prior Chelydra Taxonomy

28. Prior Taxonomy Ranges

29. Current Chelydra Taxonomy

30. Arid Regions of
North and South America

31. “this species furnishes a case of distribution
unparalleled among reptiles, ranging as it does
from the (nearctic) cold regions of Canada to
the torrid region of Ecuador” (Cope, 1868)

32. Extirpation of C. serpentina
West of the Continental Divide

33. Great Basin
Past and Present

34. Biochemistry Primer

35. DNA

36. Linear DNA

37. Bacterial and Animal
Cell Structure

38. Animal Cell
Structure

39. Mitochondria

40. Mitochondria

41. Plasmid mtDNA
• Circular
• Haploid
• Maternal

42. Population Genetics

43. Parapatric Speciation

44. Kinosternon baurii
(Striped Mud Turtle)

45. Kinosternon subrubrum
(Eastern Mud Turtle)

46. Sterntherus minor
(Loggerhead Musk Turtle)

47. Sternotherus odoratus
(Common Musk Turtle)

48. Trachemys scripta
(Red-eared Slider)

49. Trachemys scripta Range

50. Dierchelys reticularia
(Chicken Turtle)

51. Lepomis punctatus
(Spoted Sunfish)

52. Gopherus polyphemus
(Gopher Tortoise)

53. Macroclemys temminckii
(Alligator Snapping Turtle)

54. M. temminckii
(Alligator Snapping Turtle)

55. Chelydra serpentina
(North American Snapping Turtle)

56. Chelydra serpentina
CR mtDNA Sequence

57. Chelydra Phylogram

58. Panamanian Land Bridge
7 Ma

59. The Great American Interchange
Panamanian Land Bridge

60. Plate Tectonics:
Island Continents of
South America and Africa

61. Tertiary Ocean Currents

62. Chelydra Phylogram

63. Genetic Bottlenecks:
Population Crash and Recovery
(population vs time)

64. Genetic Bottlenecks

65. Population Crashes of Chelydra
Possible Catastrophes
Impact Event
Glacial Advances
Marine Transgression
Arid Climate

66. Younger Dryas Impact Hypothesis

67. Carolina Bays
(elliptical lakes aimed at Michigan)

68. Younger-Dryas Impact Event
12.9 ka

69. Suspected Crater in Southern Ohio
(cryptoexplosion)

70. Megafaunal Extinctions

71. Comparison of Younger Dryas
Ejecta Field and Range of
M. temminckii

72. Glaciations

73. Glaciations and Interglacials

74. Milankovich Cycle

75. Glaciation Worldwide

76. Ohio Glacial Maximum

77. Megafauna Sites Found in Ohio

78. Glacial Erratic Boulder
South Euclid

79. Palynology of Soil Core Samples

80. Tree Ranges over 18,000 years
(proxy ranges for C. serpentina)

81. Percidae Species Density
(Darters)

82. Amphibian Species Density Map

83. Mammal Species Density Map

84. Terrapene carolina carolina
Transients
(Eastern Box Turtle)

85. Chelydra Hatchlings

86. Hatchling Freezing Mortality

87. Chrysemys picta Range
(Painted Turtle)

88. C. picta Clade Ranges

89. C. Picta Ranges

90. Northern and Western Range
Borders of C. serpentina

91. C. serpentina Range

92. C. serpentina Deformities

93. Comparison of
Mean July Temperature Isotherm
and C. sepentina Range

94. 18 ka Mean July Isotherms

95. Caribbean Marine Transgressions

96. Galapagos Islands

97. Temperature-dependant Sex
Determination
(TSD)

98. C. Serpentina
TSD

99. Chelydra rossignonii
(Mexican Snapping Turtle)

100. Refuge Theory

101. C. Rossignonii Range and Refugia

102. American Refugia and Flooding
Areas

103. Chelydra acutirostris
(Ecuadorian Snapping Turtle)

104. C. acutirostris Range and Refugia

105. Dehydration Study
(7 days)

106. Kinosternon leucostomum
(White-lipped Mud Turtle)
Distribution

107. Kinosternon leucostomum
(White-lipped Mud Turtle)

108. K. Leucostomum Range

109. North Eastern South America

110. Kinosternon Scorpiodes
(Scorpian Mud Turtle)

111. Kinosternon Scorpiodes
(Scorpian Mud Turtle)

112. C. Acutirostris
Colonization of Amazon Basin
Bonanza

113. “[Snapping turtles evoke
impressions of a primitive nature
and time, because of their
appearance and because they
shared the earth with the
dinosaurs; they are] entitled to
regard the brontosaur and
mastodon as brief zoological
fads.”-B. Gilbert

114. Chelydra Phylogram

115. Conclusions
• Alternating glacial and interglacial climatic
changes caused a series of genetic
bottlenecks in the North American C.
serpentina population that resulted in one
predominate CR mtDNA.
• Refugia embedded in the ranges of C.
rossignonii and C. acutirostris preserved
CR mtDNA polymorphism.

116. Recommendations
• Total genomes of peninsular and continental populations
of C. serpentina made to determine if they too are
identical.
• More genomes of C. rossignonii and C. acutirostris
should be determine to confirm that the polymorphisms
exists throughout the two populations.
• Investigate if Chelydra fossils can be found in the
northeastern hiadus region between C. sepentina and C.
rossignonii ranges.

117. Acknowledgements
Reviewers:
Dr. Ron Heyer, Smithsonian Institution
Dr. Joe Hannibal, Cleveland Museum of Natural History
Dr. Michael Hofreiter, Max Planck Institute
Dr. John Iverson* (twice), Earlham College
Dr. Chris Sheil, John Carroll University
Dr. Harry van Keulen (emeritus), Cleveland State University
Dr. George Zug* (emeritus), Smithsonian Institution
Robert R. Perry*, Trebor Specialities, Inc.
Assistance:
Dr. Brad Shaffer, University of California at Davis
Dr. Don Moll, University of Southwestern Missouri
Dr. John Avise, University of California at Davis

118. Acknowledgment

122. The End