Lizard Diversity Notes aus wildlife lec 3.1

Retile Diversity - Lizards

  • Order Squamata World:
    • 17 families of lizards
    • 11-14 families of snakes
    • Over 6000 species
  • In Australia:
    • Suborder Sauria – lizards
      • 5 families
      • 76 genera
      • 595 species
    • Suborder Serpentes – snakes
      • 7 families
      • 49 genera
      • 176 species (Cogger 1996)

Lizard classification

  • Iguania: 1230 species
  • Scleroglassa: >6000 species
  • Why did Scleroglassans diversify so much more?

Lizard diversification (Vitt et al. 2003)

  • Rudimentary vomeronasal system
  • Loss of lower temporal arch
  • Quadrate free to move
  • Powerful bite
  • Additional flexion points
  • Upper jaw flexibility
  • Capture/hold agile prey

Lizards - Five families in Australia:

  • Agamidae (dragons): 65 spp. (11%)
  • Gekkonidae (geckos): 106 spp (18%)
  • Pygopodidae (legless lizards): 34 spp. (6%)
  • Scincidae (skinks): 364 spp. (61%)
  • Varanidae (monitors): 26 spp. (4%)

Agamidae: Dragons

  • Small, rough (keeled/spinose) scales
  • Well-developed limbs
  • All but front teeth fused to side jaw
  • Front teeth = pleurodont (replaceable), conical grasping prey
  • Fixed teeth = acrodont (irreplaceable), cutting
  • All Australian species are oviparous
  • Diurnal
  • Sit and wait predators
  • Major threats – land clearing, fire, predation

Agamid Distribution

  • Old world distribution
  • Centres of diversity in Asia & Australia
  • In Australia:
    • 13 genera
    • 65 species
    • Especially diverse in arid Australia
      • Ctenophorus: 22 species (34%)
      • Diporiphora: 13 species (20%)

Gekkonidae: Geckos

  • Loose skin with small soft scales
  • Large eyes with fixed transparent spectacle
  • Vertical pupil
  • All Aust. spp. oviparous
  • Constant clutch size (2 in most)
  • Some parthenogenetic
  • Nocturnal
  • Vocalise

Gecko distribution

  • Widely distributed across the world
  • Three (or four) subfamilies
  • In Australia:
    • 18 genera
    • 106 species
      • Diplodactylus: 36 species (34%)
      • Gehyra: 18 species (17%)

Gecko Variation

  • Tails – Wide variety of forms
  • Uses of tails:
    • Locomotion, jumping
    • Fat storage (Bustard 1968)
    • Antipredator function
      • Wave when threatened or in presence of scent (Webb et al. 2009, 2010)
      • Tail > tailless in arenas with predators (Daniels et al. 1986)

Gecko Toe Pads

  • Primitive = single row of narrow scales ‘lamellae’
  • Advanced: highly modified scales ‘scansors’ integrated into groups = pads
    • Microscopic outgrowths ‘setae’ on pads
    • Terminal, basal, entire digit
    • Allows geckos to walk upside down on structures
  • Electrons from gecko spatulae and electrons from the wall molecules create electromagnetic attraction (Van der Waals forces)
  • Multiple origins of adhesive pads
  • High level of convergence
  • 'primitive' condition terrrestrial
  • Both arboreal + terrestrial species

Pygopodidae: Legless Lizards

  • Hind limbs reduced to short flaps
  • Elongated bodies, left lung shorter than right
  • Lateral undulation
  • Large eyes, fixed spectacle, vertical pupils
  • Oviparous, constant clutch size (2)
  • Closely related to geckos – within Gekkonidae?

Pygopodid Distribution

  • Endemic to Australia & New Guinea
  • In Australia:
    • 8 genera
    • 34 species
      • Delma: 17 species (50%)
      • Aprasia: 10 species (29%)

Lialis Burtonis

  • Feeds only on lizards
  • Extremely successful (Australia wide distribution)
  • Widespread, variable colour patterns
  • Ambush forager
  • Unlike most lizards, eats LARGE prey
  • Skull is long, pointed, hinged
  • Snout bends at fronto-parietal joint between the eyes
  • Deflection at joint to 40^o
  • Middle part of maxilla is concave ventrally – curved upper jaw
  • Most pygopodids blunt teeth
  • Lialis = fine, sharply pointed recurved teeth
  • Hinged & bend backwards (Patchell & Shine 1986)

Aprasia

  • 10 species, all burrowers
  • Highest diversity in southern arid Australia
  • Highly polished scales
  • Feed entirely on ants + brood (Webb & Shine 1994)
  • No teeth on upper jaw
  • Very similar morphology to Leptotyphlops
  • Like blindsnakes ‘binge feeders’
  • How do they locate ant nests?
  • Do they sequester ant toxins?
  • Are they resistant to ant stings?

Scincidae: Skinks

  • Scales reinforced by osteoderms
  • Enlarged scales (shields) on head
  • Morphologically very diverse
  • Oviparous or viviparous (or both)
  • Widespread throughout Australia

Skink Distribution

  • Cosmopolitan distribution
  • Largest lizard family
  • In Australia:
    • 36 genera
    • 364 species
      • 61% of Aust lizard spp.
      • 46% of Aust reptile spp.
      • Ctenotus: 87 species (24%)
      • Lerista: 77 species (21%)

Limb Reduction in Skinks

  • Occurred a number of times in skinks
  • Associated with a fossorial lifestyle
  • Most variation shown within Lerista - from well-developed limbs to totally limbless

Varanidae: Goannas

  • Loose skin with small scales
  • Long body, long & slender neck
  • Strong, clawed limbs, muscular tail
  • Forked tongues (like snakes)
  • Arboreal, terrestrial, rocks, aquatic
  • Vary greatly in size
  • Diurnal
  • Oviparous

Varanid Distribution

  • Africa, Middle East, Asia, Australia
  • ~40 species, all in genus Varanus
  • In Australia: 26 species, most in tropics

Varanid Biology

  • Parental care
    • Lay eggs in termite mounds (V. varius, V. rosenbergi)
    • Mum digs escape hole
  • Extremely good sense of smell (eggs, live prey)
  • Eat just about anything!
  • Aquatic species (V. mitchelli, V. mertensii) declined after toads invaded