Reptiles

BIOL 4270

BC Lizards and Snakes

LizardsEuropean Wall Lizard (introduced)Northwestern Alligator LizardPigmy Short-horned LizardWestern Skink

SnakesCommon Garter SnakeGreat Basin Gopher SnakeNight SnakeNorthern Pacific RattlesnakeNorthwestern Garter SnakeRubber BoaSharp-tailed SnakeWestern Terrestrial (Wandering) Garter SnakeWestern Yellow-bellied Racer

BC Lizards and Snakes

LizardsEuropean Wall Lizard (introduced)Northwestern Alligator LizardPigmy Short-horned LizardWestern Skink…well, OK, we’ll actually look at the five-lined skink, but pretty close

SnakesCommon Garter SnakeGreat Basin Gopher SnakeNight SnakeNorthern Pacific RattlesnakeNorthwestern Garter SnakeRubber BoaSharp-tailed SnakeWestern Terrestrial (Wandering) Garter SnakeWestern Yellow-bellied Racer

Common five-lined skink (Plestidon fasciatus)

Juveniles display a bright blue tail and five lines down their back; fades to a bronze colour when they mature.

Found in a variety of habitats, including rocky outcrops, dunes, and sandy areas. Cover objects, such as rocks and wood are important for thermoregulation, hiding, and nesting.

If captured, can drop its tail, which will continue to thrash for minutes and provide distraction for the skink to escape.

Generally eat insects, crustaceans, earthworms, arachnids, and may cannibalize other smaller skinks. In turn, predated upon by hawks, raccoons, foxes, weasels, small mammals.

Biggest threats are habitat loss and degradation.

Observation: Skinks are widespread across the eastern US/Canada, but contain several disjunct populations

Question 1: Can we detect genetic structuring?

Question 2: What historic factors may account for the contemporary patterns of genetic structuring?

Widespread distribution across eastern NA

Sampling sites – red dots

Dark black borders represent the species range, with disjunct populations shown as well.

Observation: Widespread distribution with several disjunct populations.

Question: Are genealogical patterns in mtDNA spatially and temporally consistent with fragmentation due to refugial and post-glacial dynamics?

Test 1: Examine phylogenetic relationships among populations

A couple notes on skink sampling….

So, what do these data tell us?

1) Longitudinal (east-west) patterns are consistent with fragmentation due to refugial and post-glacial dynamics (i.e., different refugia for eastern and western groups)

2) Deep divergences likely imply historical processes that pre-date the Pleistocene

3) Some crazy refugia are likely – like a northern refugium in Wisconsin!

4) Mississippi River likely served as a barrier, Appalachians not a barrier

Similar patterns of strong genetic structuring with Western Skinks?

Back to lizards and snakes

Squamates are the most recent and diverse products of diapsid evolution – roughly 95% of all known living nonavian reptiles

Lizards appeared in the Jurassic period, but really began their diversification in the Cretaceous, when dinosaurs were at the climax of their diversity

Snakes appeared during the late Jurassic, likely evolving from a group of lizards whose descendants include the Gila monster and monitor lizards.

Modern lizards are a diverse group that includes terrestrial, burrowing, aquatic, arboreal, and aerial members

Some familiar groups

Geckos are mostly nocturnal with adhesive toe pads, that allow them to walk upside down

Iguanas are often brightly coloured, with crests, frills, and throat fans

Tokay gecko

Marine iguana

Monitors are large, active predators

Komodo dragon

Chameleons are arboreal lizards with projectile tongue and colour change

Panther Chameleon

Most lizards have moveable eyelids, whereas snakes eyes are permanently covered with a transparent cap.

Lizards have keen vision for daylight (retinas rich in both cones and rods) – though the nocturnal geckos have retinas composed entirely of rods

Hearing in lizards is generally poor, except for groups like geckos who use vocalizations for territoriality

Many lizards are well-adapted to hot, arid regions of the world.

Lipids in thick skin minimize water loss (as does excretion of uric acid)

Gila monsters in the US southwest store fat in their tails, which they use during drought to provide energy and metabolic water.

Snakes

Snake FeedingUnlike lizard skulls, which have a limited ability to open their jaws (and thus are restricted to eating small prey), snakes have a highly kinetic skull which enable them to eat prey several times their own diameter.

Two halves of the lower jaw are joined only by muscles and skin, allowing them to spread widely apart. Many of the skull bones are also loosely articulated, allowing the skull to flex and accommodate large prey.

Other sensesVision: poor (except for arboreal snakes)

Hearing: no ears or tympanic membrane, but do have internal ears that work well in a limited low-frequency range (100-700 Hz). Sensitive to vibrations

Smell: Typical olfaction in the nose, but not well developed. However, have Jacobson’s organs – a pair of pit-like organs in the roof of the mouth lined with richly innervated chemosensory epithelium. Forked tongue collects scent molecules and draws them past the Jacobson’s organs.

Other: Pythons, boas, and pit vipers have heat-sensitive pit organs located between their nostrils and eyes. Respond to long-wave infrared, sensitive to heat emitted by birds and mammals. Can distinguish temperature differences of 0.003 C from a radiating surface

http://www.youtube.com/watch?v=lySW2-eYilg

Tuataras

Only 2 extant species

Sphenodon punctutatus Sphenodon guntheri

Both exist solely in New Zealand on several islands (extirpated from mainland)

Garnered interest due to similarity to early Mesozoic diapsids (200mya) and represents one of the slowest rates of morphological evolution in vertebrates

Even in the few restricted areas in which tuatara exist, invasive species are still an issue.

Whenuakara Island was invaded by Norway rats in 1982 – led to the elimination of the entire local population (130 tuatara).

Order: Crocodilia

Crocodiles, alligators, caimans, and gharialsModern crocodilians and birds are the only survivors of the archosaurian lineage that gave rise to the great Mesozoic radiation of dinosaurs and their kin.

Crocodilians belong to a clade that began diversifying in the late Cretaceous, but differ little structurally from crocodiles from the early Mesozoic

Alligators and caimans(New World)

Crocodiles(widely distributed)

Gharials(India, Burma)