Amphibian Diversity

Animal Diversity

Introduction

  • The lecture focuses on amphibians and their evolutionary history.
  • The lecturer is Dr. Rhys Jones, and the lecture hall is W1.18.

The Transition from Water to Land

  • Approximately 350 million years ago, during the Carboniferous period, a significant event occurred: fish began to move onto land.

Carboniferous Period

  • Occurred around 350 Ma (million years ago).
  • Key characteristics:
    • Atmospheric Oxygen: 35%
    • Thermoregulation: Enabled animals to adapt to varying temperatures on land.
    • Lower rate of predation compared to aquatic environments.
    • New niches and territories became available.
    • Low competition for resources initially.
    • Abundance of prey (e.g., insects) on land.

Lobe-Finned Fish

  • Lobe-finned fishes are significant because tetrapods (four-limbed vertebrates) evolved from them.
  • Examples:
    • African lungfish (Protopterus annectens)
    • Mudskipper (Periophthalmus spp.)
    • Coelacanth (Latimeria sp.)
    • Australian Lungfish (Neoceratodus forsteri)

Tetrapod Evolution

  • Tetrapods evolved from advanced lobe-finned fish during the Devonian Period (approximately 410 to 355 Ma).
  • Specifically, they evolved from Rhipidistians.
  • Characteristics of Rhipidistians:
    • Lost their dorsal fins.
    • Most of the gill arches were lost.
    • They could breathe air.
    • They shared many skull characteristics with primitive tetrapods.

Tiktaalik roseae

  • An important transitional fossil between fish and tetrapods.
  • Age: 375 million years old.
  • Location: Ellesmere Island, Nunavut, Canada.
  • Size: 90cm – 275cm.
  • Nickname: ‘Fishapod’.

Ichthyostega

  • A transitional fossil between fish and tetrapods.
  • Possessed a fish-like tail and gills.
  • Had an amphibian-like skull and limbs.

First Amphibians

  • Triadobatrachus: Early Triassic; considered the first protofrog.
  • Vieraella: Early Jurassic; the first known true frog.
  • Karaurus: Early Jurassic; the first known true salamander.

Phylogeny of Amphibians

  • The consensus phylogeny shows the relationships between the major lineages of amphibians:
    • Frogs (Anura): Includes clades like Natatanura, Sooglossoidea, Myobatrachoidea, Calyptocephalellidea, Nobleobatrachia, Heleophrynidae, Anomocoela, and Xenoanura.
    • Salamanders (Caudata): Includes clades like Costata, Amphicoela, Plethodontoidea, Proteidae, Salamandroidea, and Sirenidae.
    • Caecilians (Gymnophiona): Includes clades like Teresomata and Diatriata.
  • Each group contains various families and species with specific numbers indicated in the phylogeny.

Anura (Frogs)

  • Examples:
    • European fire-bellied toad (Bombina bombina)
    • Panamanian golden frog (Atelopus zeteki)
  • Taxonomy: There is no strict taxonomic distinction between the terms ‘Frog’ and ‘Toad’.

British Anura

  • Common Toad (Bufo bufo)
  • European common Frog (Rana temporaria)

Caudata (Salamanders)

  • Salamanders, Newts, Axolotls, Mudpuppies, Olms, and Sirens.
  • Examples:
    • Fire Salamander (Salamandra salamandra)
    • Smooth (Lissotriton vulgaris) and Palmate (Lissotriton helveticus) newts
    • Great crested newts (Triturus cristatus)

Giant Salamanders

  • Chinese giant Salamander (Andrias davidianus)

Other Salamanders

  • Olm (Proteus anguinus)
  • Mud puppy (Necturus m. maculosus)

Neoteny

  • Neoteny (the retention of juvenile features in the adult form) has been observed in all salamander species.
  • Example: Axolotl (Ambystoma mexicanum)

Gymnophiona (Caecilians)

  • Caecilians are a group of limbless amphibians.
  • Examples:
    • Dermophis mexicanus
    • Boulengerula taitanus

Amphibian Reproduction

  • Amphibians often require a water source to reproduce.

Returning to Water to Breed

  • Llandrindod Wells: The site of the first Toad Crossing sign in the UK.
  • Significant road mortality: Approximately 20 tonnes of toads are killed on British roads every year.

Amphibian Eggs

  • Examples:
    • Great crested newts embryo (Triturus cristatus)
    • Smooth newt egg (Lissotriton vulgaris)
    • Toad spawn (Bufo bufo)
    • Frog spawn (Rana temporaria)

Poison Dart Frogs

  • Examples:
    • Strawberry poison-dart frog (Oophaga pumilio)
    • Cream backed poison Frog (Colostethus subpunctatus)

Other Amphibians

  • Common midwife toad (Alytes obstetricans)
  • Tangara frog (Physalaemus pustulosus)

Pouched and Darwin's Frogs

  • Pouched frogs (Assa darlingtoni)
  • Darwin's frog (Rhinoderma darwinii)

References

  • Amphibian and Reptile Conservation (http://www.arc-trust.org/)
  • Brito, P.M., et al. (2010) The histological structure of the calcified lung of the fossil coelacanth Axelrodichthys araripensis (Actinistia: Mawsoniidae). Palaeontology, 5: 1281-1290.
  • Gaining Ground: The Origin and Early Evolution of Tetrapods (Life of the Past), Indiana University Press, (2002) ISBN 978-0253340542.
  • Genome 10K Community of Scientists. (2009) Genome 10K: A proposal to obtain whole-genome sequence for 10,000 vertebrate species. The Journal of HeredityNov-Dec;100(6):659-674. DOI: 10.1093/jhered/esp08610.1093/jhered/esp086. PMID: 19892720; PMCID: PMC2877544.
  • Hedges, S.B., Kumar, S. (2009) The Timetree of life. New York: Oxford University Press; 572 pp.
  • Laurin, M., Girondot, M., and Ricqlès. A., (2000) Early tetrapod evolution. Trends in Ecology and Evolution 15(3): 118-123.
  • Lee, M. S. Y. and Anderson, J. S. (2006) Molecular clocks and the origin(s) of modern amphibians. Molecular Phylogenetics and Evolution 40: 635–639.
  • Lee, H.J., Martinez, C.A., Hertzberg, K.J., Hamilton, A.L., Graham, J.B. (2005) Burrow air phase maintenance and respiration by the mudskipperScartelaos histophorus (Gobiidae: Oxudercinae). The Journal of Experimental Biology 208 (Pt 1): 169–77.
  • Molnar, J.L., Pierce, S.E., Clack, J.A., Hutchinson, J.R. (2012) Idealized landmark-based geometric reconstructions of poorly preserved fossil material: a case study of an early tetrapod vertebra. Palaeontologia Electronica 15 (1) 32; palaeo-electronica.org/content/issue-1-2012-technical-articles/165-digital-fossil- restoration.
  • National Amphibian and Reptile Recording Scheme (http://www.narrs.org.uk/whatisnarrs.htm).
  • Shu, D.-G., Conway Morris, S., Han, J., Zhang, Z-F., Yasui, K., Janvier, P., Chen, L., Zhang, X.-L., Liu, J.-N., Li, Y. and Liu, H.-Q. (2003) Head and backbone of the Early Cambrian vertebrate Haikouichthys. Nature 421: 526-9.
  • The British Herpetological Society (http://www.thebhs.org/join.html).
  • Wilkinson, M., San Mauro, D., Sherratt, E., Gower, D.J. (2011) A nine-family classification of caecilians (Amphibia: Gymnophiona). Zootaxa 2874: 41–64.