It is easier to study the evolutionary relationships among related…
A. Species within a Genus.
B. Families within an Order.
C. Phyla within a Kingdom.
It is easier to study the evolutionary relationships among related…
A. Species within a Genus.
B. Families within an Order.
C. Phyla within a Kingdom.
WHY? Deep phylogenetic splits are usually heavily impacted
by convergence and heterochrony.
At this scale how valuable are outgroups?
WHY NOT NEWLY DIVERGED TAXA? Recent splits are
difficult to study because of a lack of informative characters?
Also, this scale suffers from parallel evolution and vicariance.
Origin and Relationships of Modern Amphibians
Things I
actually know
something about
(I’m no herpetologist)
This is like a detective novel where we are trying to find
out what happened 400+ MYA.
Don’t forget there are plenty of false clues—many groups
evolved in a short period of time, and the available fossils
are often side roads of evolution.
Sarcopterygii—Lobe Fin Fishes
a.
b.
c.
d.
e.
Appendages are Similar in Structure to Amphians
Most Modern Forms Use Them for Locomotion
1) Walk on Bottom
2) Swim
Two Major Groups
Coelacanths—2 Living Fossils from Indian Ocean
Lungfish
1) 1 Species each in Australia, Africa, and South America
2) Sister to Terrestrial Vertebrates
3) Australian Species is Very Different
a) Walks on Bottom of Ponds/Streams
b) Very similar to Paleozoic and Mesozoic forms
4) South American + African Forms
a) Gills Mostly Remove Carbon Dioxide
b) Drown Without Air
c) African Form Aestivate
d) Both Originally Considered Salamanders
(Images from Pough et al.,
Vertebrate Life)
Pugh et al., 2002. Vertebrate Life, Fig 7-5
Late Carboniferous of Europe--Any place to look for this around here?
2 Competing Hypotheses for Terrestrial Vertebrates
1. Drying pond hypothesis
a. lobe-finned fish in drying ponds
b. fish crawl to deeper ponds
c. problems
1) fish go back to water?
2) African lung fish aestivate
3) Fossilized remains in burrows
4) Oldest fossils are in brackish areas
2. Edge of the sea hypothesis
a. lobe-finned fish at the edge of the water
b. feed on prey that falls in
c. become more agile at darting out of the surf
d. dry land is free of competitors
e. Problems
1. Some modern fish do jump ponds
2. Why are they gone?
Here is One Recent Idea of Relationships
(Images from Pough et al.,
Vertebrate Life, and
Herpetology)
Here is Competing Idea of Relationships
Amniotes
Why do we see these differences
The traditional view has always assumed a
close relationship between temnospondyls
and modern Amphibians. Thus outgroup
and character selection may be biased
How do these biases impact the results of the study?
LET’S PLAY CLUE
Maybe it was ……
a “Branchiosaur (a “temnospondyl” ……
in the Permian…..
via paedomorphosis.
Explains: Small size, Combination of Primitive +
Derived Characters, Difficulty Pinning Things Down,
Absence of Last Bones to Develop in Branchiosaurs
(Supratemporals, Pre+Postfrontals, Jugals,
Parietal, Lacrimals), Large Orbits, Tooth Structure.
Matches Fossil Developing Branchiosaurs
BUT—Testing requires complete phylogenetic information.
SO WHAT ABOUT LISSAMPHIBAINS
Urodela
Anura
Can We Do Any Better?
Are they Monophyletic?
Gymnophonia
Synapomorphies Supporting Lissamphibian Monophyly
1.
Teeth are Pedicilate and Bicuspid
2. Ears are unique having a stapes and operculum
(not present in caecillians) and a
unique patch of sensory epithelial cells
(papilla amphibiorum--detects low frequency sounds)
3. Stapes is directed dorsolaterally vs ventrolaterally
(shared by some probable relatives)
4.Fat bodies develop from different germ layer (germinal ridge)
5. Skin contains Mucus and poison glands
6. Green Rods Present in Frogs and Salamanders
7. Muscle beneath Eye Allows Elevation
(used in breathing + Swallowing)
8. Buccopharyngeal Pump for Respiration
(use throat like a billows). Means air is pushed
into the lungs
9. Short Strait Ribs
10. 2 Occipital Condyles (Shared with Mammals)
11. Reduction of Many Cranial Elements
SO WHAT ABOUT LISSAMPHIBAINS
Urodela
Anura
Gymnophonia
This arrangement supported by: Soft Anatomy
(Presence of a tail, costal groves)
SO WHAT ABOUT LISSAMPHIBAINS
Urodela
Anura
Gymnophonia
This arrangement supported by:
Skeletal Anatomy + Combined Morphological and Genetic Data
(What does this tell you about the # of soft characters used?)
(What would a combined morphological + genetic analysis say?)
Frogs + Salamanders=Batrachia
ORDER: URODELLA
I.
Characters
A. Long Tail
B. Four Limbs
C. Costal Grooves
D. Paedomorphosis is Common (aquatic salamanders)
II. Fossil Record Dates to Middle Jurassic (170-159 MYA)
A. Use of Caudata
B. Difficulties of Metamorphosis
III. Biodiversity
A. 515+ Species
B. Many Cryptic Species
C. Mainly Holoarctic (recent invasion of Neotropics)
Sirenidae—Sirens
•2 Genera + 4 Species
•Primarily Indiana south and East
•Eel-Like and Aquatic
•Keratinous Beak
•No Hind Limbs
•Some of the Largest Salamanders
•Prey Primarily on Inverts
•Siren intermedia
Cryptobranchidae—Hellbenders
•2 Genera + 3 Species
•Eastern NA, China, Japan
•Mostly Aquatic
•Incomplete Metamorphosis
•Largest Indiana Salamander
•Prey Primarily on Crayfish
•Cryptobranchus alleganiensis
Amphiumidae—Amphiumas
•1 Genus + 3+ Species
•Mississippi River System
•Eel-Like and Aquatic
•Reduced Limbs
•Nasty Biters
•Prey Primarily on Aquatic Animals
•Amphiuma
Plethodontidae—Lungless Salamanders
•27 Genera + 360 Species
•Mostly NA with some in SA and Europe
•Most specious group of salamanders
•Full Metamorphosis (Mostly)
•Typically Small
•Prey Primarily on Small Inverts
•Plethodon, Eurycea, Psudotriton, Eurycea, Desmognathus
Proteidae—Mudpuppies and Kin
•2 Genera + 6 Species
•Mostly Central Europe + Necturus
•Aquatic Salamanders with Well-developed Gills+ 4 Legs
•Prey Primarily on Inverts (occasionally caught on worms)
•Necturus maculosus
Salamadridae—Newts
•15 Genera + 62 Species
•Holoarctic
•Eft Stage and Return to Water
•Complete Metamorphosis
•Highly Toxic
•Bad News for Frog Eggs
•Notophothalmus viridescens
Ambystomidae—Mole Salamanders
•1 Genus + 30 Species
•Mostly US
•Robust Bodies made for Digging
•Most Have Full Metamorphosis
(Axotyls)
•Some Paedomorphic Forms
•Prey Primarily on Inverts
•Ambystoma jeffersonianum, tigrinum, and texanum
ORDER: GYMNOPHONIA
I.
Characters
A. Short Post-Anal Tail
B. No Limbs
C. Costal Grooves?
D. Paedomorphic
II. Fossil Record Dates to Early Jurassic (190 MYA)
A. Fossils from NA (What does this mean)
B. Had Legs in Fossil Records
C. Very Similar to Salamander Legs
D. Snakes Before Snakes
III. Biodiversity
A. ~170
B. Pantropical Except Central Africa
C. Systematics are a Mess
ORDER: ANURA
I.
Characters
A. No Post-Anal Tail
B. No Limbs
C. No Costal Grooves
D. Caudal Vertebra Fused Urostyle (rod)
E. Vertebral Column Reduced
F. Elongate Hind Limbs
II. Triadobatrachus from Lower Triassic (230 MYA)
A. Madagascar
B. Poland
C. Same Arizona Deposit as a Caecilian
III. Biodiversity
A. ~4300 Species
B. Cosmopolitan Except Deserts and Tundra
C. Very Diverse In Tropics
Triadobatrachus massinoti
Modern Leptodactylus
Ascaphidae—Tailed Frogs
•Monotypic
•Ascaphus truei
•Tail is an Intermittent (“Penile”) Organ
•Highly Aquatic
•Fast Flowing Streams
•Pacific Northwest
•Tadpoles have oral suckers, which are sometimes used to climb
Paleobatidae—Spadefoot Toads
•3 Genera + 11 Species
•NA, Europe, and North Africa
•Keratin Spade on Foot
•Used to Dig
•Animals Emerge During Heavy Rains
•Explosive Breeders
•Rapid Metamorphosis
•Scapheopus holbrooki, Spea bombifrons
Bufonidae—Toads
•33 Genera + 455 Species
•Once a Trashcan
•Nearly Cosmopolitan
•Many are Terrestrial as Adults
•Highly Toxic Skin Glands (Parotid)
•Maintain Bidder’s Organ (Rudimentary Ovary
•No Teeth
•Bufo woodhousi and americanus and maritimus
Pipidae—Clawed Frogs
•5 Genera + 30 Species
•Sub-Saharan Africa, Panama, Tropical South America
•Aquatic as Adults
•Odd Morphology
•Lack Tongues
•Claw-like Tips to Toes
•Dorsoventral Compression
•Well-developed Lateral Lines
•Official Lab Rat of Developmental Biology
•Xenopus
Myobatrachidae
•23 Genera + 122 Species
•Australia, New Guinea, Tasmania
•Highly Variable Reproduction
•Young in Inguinal Pouches of Males
•Young in the Stomach
•Many falling victim to chytid fungal infections
Hylidae—Tree Frogs
•40 Genera + 835 Species
•Paraphyletic with “Psuedidae” excluded
•Mostly Arboreal
•Toe Pads and claw-like terminal phalanges
•2 Hyla, 2 Psuedacris, Acris
Microhylidae—Narrowmouth Toads
•69 Genera + 350 Species
•Eastern US, South America, Southern Africa
•Small Palatal Folds--Head Vail
•Very Small Frogs
•Local Versions are Fossorial
•Other places get Terrestrial and Arboreal Forms
•2 Form Commensal Relationships with Spiders
•Often Found Under Cow Poop
•Gastrophryne
Dendrobatidae—Poison Dart Frogs
•8 Genera + 205 Species
•Central and South America
•Terrestrial or Arboreal
•Parents Cary Tadpoles on Backs
•Highly Toxic Skin Glands
•Used to Poison Blow-gun Darts
•Probably Diet Related
•Common in Pet Trade
•Official Lab Rat of Developmental Biology
•Dendrobates
Mantelliidae—Madagascar Poison Frogs
•5 Genera + 140 Species
•Madagascar
•Have Aposematic Coloration and Poison in Mantellus
•Some Mantellus also resembles Rana and Bufo
•2 Genera Converge on Spea
•Boophis resembles Hyla
•Why do we see these patterns?
•What is the difference between convergence and parallelism?
Ranidae—Pond Frogs
•38 Genera + 600+ Species
•Cosmopolitan
•Highly Variable and Para/Polyphyletic
•Trashcan taxon
•Economically Important
•Rana catesbienna widely Introduced
•8 Local Species
ILLUSTATION OF DIVERSITY: OTHER FAMILIES
•Leiopelmatidae
•Bombinatoridae
•Discoglossidae
•Megaphyridae
•Pelodytidae
•Rhinophrynidae
•Brachycephalidae
•Heleophrynidae
•Racophoridae
•Leptodactylidae
•Rhinodermatidae
•Pseudidae
•Allophrynidae
•Hemisotidae
•Artholeptidae
•Petropedetidae
•Hyperoliidae
Mostly in African, SA, and Asiatic Tropics