In Your Face: Geology and Vertebrate Natural History of Australia
Geology BasicsRock types:
Bubble in basalt flow - Santiago, Galapagos Islands
Ortega Quartzite, Picuris, NM
Supai Group sandstone, Bright Angel Trail, Grand Canyon
In Australia, we will mostly be concerned with sedimentary and igneous rocks. Some highlights:
Northern Territory: The Arnhemland Escarpment dominates the landscape. It is made entirely of one rock unit - the sedimentary Kombolgie Formation, representing ancient continental river and alluvial fan deposits. Why is it special? 1.7 billion years old and an extremely hard topography dominator.
But the real geologic standout is the Great Barrier Reef - the worlds primer factory for carbonate rocks. But why is this region such a great site for reef building?
Equilibrium constants An equilibrium constant is equal to the concentration of products over reactants. In the case of carbonate system we see the following equilibrium constants:
|CO2 + H2O -> H2CO3||(K3 = 1*10-1.43)|
|H2CO3 -> H+ + HCO3-||(K3 = 1*10-6.40)|
|>HCO3- -> H+ + CO32-||(K3 = 1*10-10.33)|
|Ca2+ + CO32- -> CaCO3||(K3 = 1*10-8.33 for aragonite and 1*10-8.48 for calcite)|
Looking at this reaction series, you would think that adding more CO2 would drive the reactions toward the right and increase CaCO3 precipitation, but this is not the case:
- Globally in the shallow marine tropics
- Locally in places where topography favors shallow water clear of nasty sediment.
Incredible Vertebrate DiversityOn the right is a cladogram of all of the major vertebrate groups. The wonder and glory of the Australia travel study is that it is possible that we could see representatives of each one. That could possibly even include the Australian lungfish (albeit unlikely.)
That's far more vertebrate diversity than I we address here. For this half hour, I want to consider the critters in red that include some of the most conspicuous animals we will see. Dr. Thompson has discussed Australian mammals. Please feel free to examine my notes from the 2015 trip as well. I focus on the other two groups:
SquamataAustralia has been called "the land of lizards," both because it is home to an interesting endemic radiation of squamates and because they are fantastically diverse, with over three times as many species as live in North America.
There are hundreds of living squamate species. All of their diversity falls into two major groups:
These groups appear in the Early Jurassic, with essentially modern looking forms occurring in the Cretaceous.
Gilbert's dragon Amphibolurus gilberti
Iguania:Contains a great diversity of smaller groups. In North America we are familiar with: The use of the tongue in prey capture.
Australian iguanians are represented by the taxon Agamidae, whose members are referred to as "dragons." Common examples include:
- They retain a row of modified scales down the middle of their back
- They tend to have large powerful legs.
Yellow-spotted monitor Varanus panoptes
Scleroglossa:Contains familiar North American groups including:
- varanids (aka monitors or goannas) - Small to large lizards like the Yellow-spotted monitor (right) that have come to occupy top predator niches usually reserved for mammals. Living varanid lizards are able to elevate their metabolic rates by using gular pumping of the hyoid skeleton to ventilate the lungs more efficiently. Today's varanids are a sad remnant of earlier glory. Consider Megalania prisca, the giant monitor of the Pleistocene. Today, the largest Australian monitor is the perentie.
- Pygopodids - limbless geckos.
- Lots more skinks - Burrowing lizards in North America, their Australian cousins occupy many "normal lizard" niches and are very common.
- Mosasaurs - marine lizards of the Cretaceous
Varanus panoplies senses its environment
- A scaled tongue. In some this facilitates the division of the front of the tongue into a sensory organ.
Oxyuranus microlepidotus the fierce snake - world's most poisonous
Dreadful SnakesSnakes are scleroglossans. In Australia one group predominates: Elapidae. Familiar as coral snakes and cobras.
- Of the world's ten most venomous snakes, nine are Australian elapids. Number one: The fierce snake Oxyuranus microlepidotus (right). Ones we might actually see:
Why all the scary snakes? Two thoughts:
- Desert ecology - food is rare so selective advantage to those who waste not.
- Prolonged evolutionary arms race with skinks, their primary food.
In an odd reversal, Viperidae (the vipers) is completely absent form Australia. In fact one group of elapids - the death adders - has convergently evolved a viper-like morphology.
Calyptorhynchus banksii the Red-tailed black cockatoo - loveliest of birds
BirdsThe birds of Australia are like the animals of Australia in microcosm:
- Sampling great taxonomic diversity
- Embodying interesting evolutionary lessons
Our trip should enable us to get close to some of the world's most charismatic bird species (right) including creatures that you would pay thousands of dollars to own as an exotic pet.
DiversityWe can reasonably hope to see examples of the three major monophyletic groups of birds:
- Ratites - Large (mostly) flightless birds: ostriches, emus, cassowaries, rheas, kiwis
- Galloanserae - the game birds:
- Galliformes - quail, pheasants, guinea-fowl, etc.
- Anseriformes - ducks, geese, and a few odd-balls
- Neoaves - everything else
Dromaeus novaehollandae - Emu
Ratites:The Emu - Dromaeus novaehollandae: A large flightless bird inhabiting most of the continent with:
- reduced wings (in contrast to ostriches and rheas)
- fruit and insect eating
- inhabits open woodland in small flocks (herds?)
Mating: Emus are polyandrous, with females mating with a number of males and distributing her eggs among their nests. Males care for the offspring, who may be either full or half siblings. Because males are the limiting gender in this system, females develop garish display coloration and display to attract males.
Casuarius casuarius - Southern cassowary father and juvenile
- more robust and muscular
- with a keratin casque on top of head
- dark plumage with garish skin and wattles
- solitary inhabitant of dense rain forest
Ecology: Critically endangered by the encroachment of humans into their habitat. Cassowaries have a bad reputation, being the only bird ever known to kill humans. That was over a century ago, but they can be aggressive.
Alectura lathami - Australian Brush Turkey
Galloanserae 1: GalliformesMegapodes, incuding the Australian Brush Turkey - Alectura lathami: Australia boasts an odd group of galliform birds, the megapodes. We are likely to see:
- the Australian brush turkey - Alectura lathami (right) in Queensland
- the orange-footed scrub-fowl, Megapodius reinwardti in the Northern Territories and Queensland
Nesting: All birds incubate their eggs. Megapodes, however, don't use their bodies. Rather, the males heap mounds of rotting vegetation over them, and use the heat they give off for incubation. Males carefully monitor the nests, adding and subtracting material as necessary to maintain the right temperature. Upon hatching, the extremely precocial chicks emerge and fend for themselves.
Anseranas semipalmata - Magpie goose
Galloanserae 2: AnseriformesMagpie geese, Anseranas semipalmata: Australia has many ducks and geese, but also one common species that is neither duck nor goose, the magpie goose:
- endearingly ugly.
- common and put to an amazing range of uses by aboriginal cultures.
And with luck we will see the Australian swan.
Neoaves:The phylogenetic patterns we saw above was recovered in the early days of cladistics. But Neoaves, the majority of birds, was utterly intractable until about ten years ago when combined molecular/morphological analyses began yielding consistent results. As a result we saw that Neoaves contains Inopinaves, a large clade containing the majority of land birds. This has recently been confirmed by Prum et al., 2015. It presents a very interesting pattern:
- Falcons are not members of the group (Accipitriformes) containing hawks, eagles, and vultures.
- Kingfishers, woodpeckers, toucans, and some other groups are close relatives (Coraciimorpha).
- Parrots and perching birds (Passeriformes) are sister taxa. (Potential synapomorphy: Vocal learning)
- Seriemas, falcons, parrots, and passeriforms belong to Australaves. (What could that mean?)
Their last common ancestor seems to have lived in the lands around southwest Pacific around 50 million years ago.
When we visit Australia, we will be seeing the place where this radiation happened, and observing members of the most basal branches.
Blue-faced honeyeater Entomyzon cyanotis
Honeyeaters:A speciose group of nectar-fruit specialists. We will see these at every stop on the trip. First encounter, the noisy miners of Sydney.
Australian magpie Gymnorhina tibicen
Artamids:Closely related to, but distinct from the corvids (crows, magpies, jays), Artamidae contains crow-sized passerines that ecologically converge on birds of prey. Some like the pied butcher bird have heavy hooked beaks.
Little Corella Cacatua sanguinea
Cockatoos:An Australia-New Guinea radiation of parrots that make up some of Australia's most common and charismatic birds:
- highly valued as pets (including the beloved cockatiel)
- despised as agricultural pests
Cockatoos encompass a range of morphology and color. Some groups are:
- White: E.G.: Little corella (right) and sulfur-crested cockatoo
- Black: E.G.: Red-tailed black cockatoo
- Pink: E.G.: Rose breasted cockatoo
- erectable crests
- feathers that slough off a powder
Collared lorikeet Trichoglossus rubritorquis
Lorikeets:An Australasian-southeast Asian radiation of specialized nectar eating birds:
- employ specialized brush-like tongues
- are among the most colorful parrots
Red-winged parrot Aprosmictus erythropterus
Psittacoidea - Proper parrots:Australia is home to 35 species of other parrots. We are likely to see the Red-winged parrot (right). Maybe, if the wind blows from the desert, we might see:
- Wild budgerigars