1. Amphibians!
Review the general taxonomy and biology of amphibians, as well as global patterns of distribution and diversity.
Discuss important groups of amphibians in North American freshwater systems: life cycles, reproduction, habitat requirements, and patterns of diversity.
For the amphibians, you are responsible for knowing the information on both the ORDERS and FAMILIES we discuss in lecture.

2. Amphibians?
“These foul and loathsome animals are abhorrent because of their cold body, pale color, cartilaginous skeleton, filthy skin, fierce aspect, calculating eye, offensive smell, harsh voice, squalid habitation, and terrible venom; and so their Creator has not exerted his powers to make many of them.”
- Linnaeus, 1758

3. Amphibian Taxonomy
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia

4. Amphibian Evolution
Of the living vertebrates, amphibians were the first to adapt to extended periods of time on land.
Most still need fresh water at some point in life cycle.
These multiple habitat requirements are reflected in the complex life cycle of most (but not all) species.

5. The Complex Life Cycle
Costs and Benefits?

6. Major Challenges of Life on Land
Support and locomotion
Respiration

7. Support and Locomotion
Vertebrae form a suspension girder, with weight hung beneath the vertebral column
Weight transferred through pelvic and pectoral girdles to limbs
Inefficient: splay-legged instead of legs rotated beneath body

8. Respiration Lungs, but no efficient way of filling and emptying
To compensate, they have moist skin with embedded blood vessels
CO2 released and O2 absorbed by diffusion across semi-permeable membrane (i.e., water layer).
Semi-permeable membrane necessary for concentration gradient that “directs” movement of CO2 released and O2.

9. The Living Orders of Amphibians
Gymnophiona
Salientia
Caudata

10. Order Gymnophiona (aka, Caecilians)
162 species
Limbless
Up to 1.5 m long
Tentacle between eye and nostril – sensory organ
Oviparous and viviparous

11. Global Distribution of Gymnophiona

12. Gymnophiona Life History, Reproduction, and Ecology
We don’t know much
Extended breeding in tropics, across multiple seasons
Primarily fossorial, but also aquatic

13. Order Salientia 3438 species!!
No scientific distinction between frogs and toads
Frogs are typically smooth-skinned, have long hind limbs for leaping, and live in or near water
Toads have warty, drier skin, with shorter hind limbs , and live on land – but most still return to water to breed

14. Global Distribution of Salientia

15. Mechanics of Reproduction in Salientia
Amplexus
External fertilization

16. Salientia Life History and Reproduction:
Tropics
Reproduction throughout year, with rainfall as the primary cue
Need water, but not necessarily ponds / streams
High diversity of reproductive strategies

17. Gastric Brooding Frog Rheobatrachus vitellinus

18. Poison Dart Frogs Family Dendrobatidae

19. Borneo Tree-Hole Frog Metaphrynella sundana

20. Salientia Life History and Reproduction:
Temperate Zone
Reproduction is seasonal and dependent on combination of temperature and rainfall
Generally happens in ponds and lakes
Explosive (i.e., during brief period of time)

21. Salientia Life History and Reproduction
Explosive Breeding
Tadpoles scape algae and diatoms from substrate

22. Salientia Ecology: Environmental Controls on Larval Development and Survival
Hydroperiod
Canopy cover
Phenotypic plasticity

23. Salientia Ecology: Environmental Controls on Larval Development and Survival
Hydroperiod

24. Hydroperiod Period of time a pond had standing water
Species often matched to particular hydroperiods, ranging from days to permanent
Adaptation to hydroperiod often represents a trade-off

25. The Hydroperiod Trade-Off
Short
Low competition / predation
Fast development
Long
High competition / predation
Slow development

26. Hydroperiod as Primary “Filter” of Amphibian Community
Adults
Hydroperiod
Sp.X
Sp.Y
Metamorphosis
Other Conditions
Larvae

27. Salientia Ecology: Environmental Controls on Larval Development and Survival
Hydroperiod
Canopy cover

28. Canopy Cover Affects light regime Affects temperature regime
Affects algal community, abundance, and composition

29. Yale Forest
(Skelly et al., 2002)

30. Whole Pond Experiment Manipulate Canopy in 7 Wetlands
Monitor Population & Community Responses
Photos are of the same pond before and after overstory removal along S shore. Enclosures are shown in left hand photo. White pvc pipe in foreground of left hand photo can be seen sticking out of ice in lower right of right hand photo.

31. Canopy Experiment Species
Photos are of the same pond before and after overstory removal along S shore. Enclosures are shown in left hand photo. White pvc pipe in foreground of left hand photo can be seen sticking out of ice in lower right of right hand photo.
Wood Frog
Rana sylvatica
Spring Peeper
Pseudacris crucifer

32. Forest Canopy and Larval Performance
Open Canopy
Spring Peeper
Wood Frog
Light
Temperature
DO2
Periphyton
Closed Canopy

33. Salientia Ecology: Environmental Controls on Larval Development and Survival
Hydroperiod
Canopy cover
Phenotypic plasticity

34. Phenotypic Plasticity
Developmental rates often fine-tuned to avoid other species that use the pond (i.e., competitors and predators)
Tadpoles of some species can change shape to increase survival or development rate in pools when stuck with predators or too many competitors
Phenotypic plasticity: Ability to “activate” different phenotypes in response to environment

35. Response to Predators Can fine-tune to respond to multiple predators
Often reversible

36. Environmental Cues Predator chemicals Dead conspecifics
Dead heterospecifics

37. Response to Competition
Reduce investment in tail to accelerate metamorphosis
Experiments control for food availability

38. Salientia Ecology: Some cool exceptions
Foothills yellow-legged frog
Tailed frog

39. Stream-breeding frogs in North America
Foothills yellow-legged frog (Rana boylii)
Sarah Kupferberg studied breeding sites along Eel River, northern CA
Timed egg-laying to avoid fluctuations in river stage and current velocity
Attached eggs to stable substrate (i.e., cobbles and boulders)
Selected wide, shallow reaches where depth would not change with discharge.

40. Stream-breeding frogs in North America
Rocky Mountain Tailed Frog (Ascaphus montanus)
Found in small (1st - 3rd order), cold streams in the northern Rockies
Males don’t call
Internal fertilization with cloacal “tail”
Lay eggs under rocks
Tadpoles develop for 3 yrs. – suck onto rocks with mouth, scrape off diatoms and insect larvae
Adults in stream during day, forage along bank at night

41. Order Caudata 352 species Salamandridae Cryptobranchidae Hynobiidae
North America is home to greatest diversity!
Salamandridae
Cryptobranchidae
Hynobiidae

42. Global Distribution of Caudata

43. Caudata Life History, Reproduction, and Ecology
Ambystomatidae (30 species)
Plethodontidae (376 species)

44. Ambystomatid Characteristics
30 species
Stout-bodied with short, rounded heads and conspicuous costal grooves
Larvae have broad heads and 3 pairs of bushy gills
Referred to as “mole salamanders”

45. Ambystomatid Life History and Reproduction
Mostly pond breeders with annual reproductive cycle
Breed in spring, initiated by saturation of ground with melting snow and spring rains
Males and females travel from uplands to congregate at semi-permanent to permanent pools

47. The Mechanics of Reproduction in Ambystomatids
Males deposit spermatophores, then females pick up with cloaca
Females attach eggs to substrate – sticks, logs, rocks
Larval development highly variable – weeks, months, multiple years in stable habitats

48. Stream-Breeding Ambystomatid Streamside salamander
Ambystoma barbouri
Streamside salamander

49. An Alternative Cycle Ambystoma opacum (Marbled salamander)
Mate on land in fall
Female selects nest site in dry or partially-dry bed of temporary pond
Make nest by burrowing cavities in ground
Embryos hatch within 1-2 days after nest submerged in spring

50. An Alternative Cycle
Ambystoma opacum
(Marbled salamander)

51. Ambystomatid Ecology
Neoteny and Cannibalism
Unisexual Populations

52. Ambystomatid Ecology
Neoteny and Cannibalism

53. Ambystomatid Ecology: Neoteny and Cannibalism
Ambystoma tigrinum

54. Neoteny: Retention of larval characteristics in mature adults (aka, facultative metamorphosis)
In cold, high-elevation ponds in CO, also in springs and cattle tanks in Mexico
Favored in stable and productive habitats, or where low temps constrain full metamorphosis
See this in other salamanders too, especially cave species

55. Neoteny
Family Proteidae
Proteus anguinus

56. Cannibalism 2 larval morphotypes in A. tigrinum
Normal eats invertebrates and zooplankton
Cannibal eats other salamander larvae

57. Ambystomatid Ecology
Neoteny and Cannibalism
Unisexual Populations

58. Ambystomatid Ecology: Unisexual Populations
Almost entirely female
New England, Great Lakes and Canadian Maritimes
Hybrids of 4 species
Single individual can have genetic components of 3 species (i.e., triploid, 3N)

59. A. laterale
A. jeffersonianum
A. tigrinum
A. texanum

60. Unisexual Ambystomatid populations
Reproduce by gynogenesis and syngamy
Reconstituted diploids (2N) don’t survive, but need diploid males for reproduction
Males supplied by immigration, or through successful reproduction with subpopulation of diploid females
Believed to be result of past hybridization

61. Plethodontid Characteristics
376 species
Lungless…WHY?
Nasolabial grooves
Males get cirri when sexually active
Terrestrial and stream-associated

62. Plethodontid Life History and Reproduction
Biennial cycle (once every 2 years)
Active at surface in forests and along streams from late spring to autumn
Mating in late summer and autumn
Oviposition in spring and early summer
Most species have aquatic larvae and terrestrial adults, but some are only terrestrial.

63. Crazy Plethodontid Courtship
Male ID sex and species via chemoreception
Male initiates tail-straddle walk, which can go on for minutes to hours!

64. Crazy Plethodontid Courtship
Male uses cirri and head slap to “deliver” mental-gland secretions to female.

65. Plethodontid Egg Sites and Parental Guarding

66. Plethodontid Distribution and Diversity: Southern Appalachians
Highest diversity in Southern Appalachians
Southern Appalachians are geologically stable
Diversity decreases moving northward
Especially diverse stream salamander communities in Southern Appalachians

67. Early species radiation among stream types
Ephemeral
Springs
Perennial

68. Lateral Habitat Partitioning in Southern App. Plethodontids

69. Lateral Habitat Partitioning in Southern App. Plethodontids

70. Plethodontid Distribution and Diversity: Central America
Second highest diversity in Central America
Central America is geologically active
Species are distributed along elevational gradient

71. Distribution along Elevational Gradient

72. Vertical Habitat Partitioning in Central American Plethodontids