Title: Amphibians!
1Amphibians!
- 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.
2Amphibians?
- 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
3Amphibian Taxonomy
- Kingdom Animalia
- Phylum Chordata
- Class Amphibia
4Amphibian 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.
5The Complex Life Cycle
Costs and Benefits?
6Major Challenges of Life on Land
- Support and locomotion
- Respiration
7Support 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
8Respiration
- 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.
9The Living Orders of Amphibians
- Gymnophiona
- Salientia
- Caudata
10Order Gymnophiona(aka, Caecilians)
- 162 species
- Limbless
- Up to 1.5 m long
- Tentacle between eye and nostril sensory organ
- Oviparous and viviparous
11Global Distribution of Gymnophiona
12Gymnophiona Life History, Reproduction, and
Ecology
- We dont know much
- Extended breeding in tropics, across multiple
seasons - Primarily fossorial, but also aquatic
13Order 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
14Global Distribution of Salientia
15Mechanics of Reproduction in Salientia
- Amplexus
- External fertilization
16Salientia 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
17Gastric Brooding FrogRheobatrachus vitellinus
18Poison Dart FrogsFamily Dendrobatidae
19Borneo Tree-Hole FrogMetaphrynella sundana
20Salientia 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)
21Salientia Life History and Reproduction
Explosive Breeding
Tadpoles scape algae and diatoms from substrate
22Salientia Ecology Environmental Controls on
Larval Development and Survival
- Hydroperiod
- Canopy cover
- Phenotypic plasticity
23Salientia Ecology Environmental Controls on
Larval Development and Survival
24Hydroperiod
- 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
25The Hydroperiod Trade-Off
- Long
- High competition / predation
- Slow development
- Short
- Low competition / predation
- Fast development
26Hydroperiod as Primary Filter of Amphibian
Community
Adults
27Salientia Ecology Environmental Controls on
Larval Development and Survival
28Canopy Cover
- Affects light regime
- Affects temperature regime
- Affects algal community, abundance, and
composition
29Yale Forest
(Skelly et al., 2002)
30Whole Pond Experiment
- Manipulate Canopy in 7 Wetlands
- Monitor Population Community Responses
31Canopy Experiment Species
Wood Frog Rana sylvatica
Spring Peeper Pseudacris crucifer
32Forest Canopy and Larval Performance
Open Canopy
Wood Frog
Spring Peeper
Closed Canopy
33Salientia Ecology Environmental Controls on
Larval Development and Survival
- Hydroperiod
- Canopy cover
- Phenotypic plasticity
34Phenotypic 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
35Response to Predators
- Can fine-tune to respond to multiple predators
- Often reversible
36Environmental Cues
- Predator chemicals
- Dead conspecifics
- Dead heterospecifics
37Response to Competition
- Reduce investment in tail to accelerate
metamorphosis - Experiments control for food availability
38Salientia Ecology Some cool exceptions
- Foothills yellow-legged frog
- Tailed frog
39Stream-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.
40Stream-breeding frogs in North America
- Rocky Mountain Tailed Frog (Ascaphus montanus)
- Found in small (1st - 3rd order), cold streams in
the northern Rockies - Males dont 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
41Order Caudata
- 352 species
- North America is home to greatest diversity!
Salamandridae
Cryptobranchidae
Hynobiidae
42Global Distribution of Caudata
43Caudata Life History, Reproduction, and Ecology
- Ambystomatidae (30 species)
- Plethodontidae (376 species)
44Ambystomatid 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
45Ambystomatid 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
46(No Transcript)
47The 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
48Stream-Breeding Ambystomatid
Ambystoma barbouri Streamside salamander
49An 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
50An Alternative Cycle
Ambystoma opacum (Marbled salamander)
51Ambystomatid Ecology
- Neoteny and Cannibalism
- Unisexual Populations
52Ambystomatid Ecology
53Ambystomatid Ecology Neoteny and Cannibalism
Ambystoma tigrinum
54Neoteny 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
55Neoteny
Family Proteidae Proteus anguinus
56- Cannibalism
- 2 larval morphotypes in A. tigrinum
- Normal eats invertebrates and zooplankton
- Cannibal eats other salamander larvae
57Ambystomatid Ecology
- Neoteny and Cannibalism
- Unisexual Populations
58Ambystomatid 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)
59A. laterale
A. jeffersonianum
A. texanum
A. tigrinum
60Unisexual Ambystomatid populations
- Reproduce by gynogenesis and syngamy
- Reconstituted diploids (2N) dont 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
61Plethodontid Characteristics
- 376 species
- LunglessWHY?
- Nasolabial grooves
- Males get cirri when sexually active
- Terrestrial and stream-associated
62Plethodontid 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.
63Crazy Plethodontid Courtship
Male ID sex and species via chemoreception
Male initiates tail-straddle walk, which can go
on for minutes to hours!
64Crazy Plethodontid Courtship
- Male uses cirri and head slap to deliver
mental-gland secretions to female.
65Plethodontid Egg Sites and Parental Guarding
66Plethodontid 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
67Early species radiation among stream types
Ephemeral
Springs
Perennial
68Lateral Habitat Partitioning in Southern App.
Plethodontids
69Lateral Habitat Partitioning in Southern App.
Plethodontids
70Plethodontid Distribution and Diversity Central
America
- Second highest diversity in Central America
- Central America is geologically active
- Species are distributed along elevational
gradient
71Distribution along Elevational Gradient
72Vertical Habitat Partitioning in Central American
Plethodontids