Australia's history is paradoxical. It has some of the oldest rocks on earth, yet its recorded history is relatively brief, usually measured from the first British colony established at what is now the city of Sydney in 1788. Yes, the Dutch and French had landed at a number of sites on the continent before this, but their visits didn't result in any long-term settlements. Also, as I noted in an earlier column (Flannery, 2011), the British pirate William Dampier landed on the west coast of Australia in 1699. When I was there last summer, I visited one of those landing sites, Shark Bay, which according to Alex George (1999) is almost as wild now as it was 400 years ago. One of the thrills of my trip to Western Australia was seeing Dampiera alata in bloom with its beautiful blue flowers (Scott & Negus, 2005). This is one of several plants named for this naturalist who brought plant, insect, and bird specimens back to England.
As far as the natural history and, especially, the botany of Australia are concerned, the French actually did more of the early work than the British. And the Dutch were a formidable enough presence that the continent was referred to as "New Holland," even after British colonization began. The name "Australia" wasn't widely used until the British naval officer Matthew Flinders argued for its adoption after he had mapped the coastline while circumnavigating the continent. As I mentioned last month (Flannery, 2012), the botanist Robert Brown was a member of Flinders's party; a number of other British biologists also arrived in Australia on navy ships. The most notable is Charles Darwin on the Beagle, which sailed into Sydney Harbor in January 1836, more than 4 years after leaving England.
Darwin in Australia
In anticipation of the 200th anniversary of Darwin's birth in 2009, the National Museum of Australia published a volume that includes extracts from his diary related to this leg of his trip, together with several commentaries (Morton, 2008). The journal entries are rather disappointing considering that Darwin is in a place filled with biological oddities, where almost every animal and plant is different from what he has seen elsewhere – except, of course, for the sheep, roses, and other organisms that the settlers had brought with them. He mentions seeing a platypus but doesn't appear to have been floored by it, nor was he struck by the dramatic geology of the Blue Mountains west of Sydney. Many of his entries refer to people rather than to animals and plants. It seems almost as if, at this point in his voyage, he has had it with travel. Enough! He is beginning to look forward to getting home, rummaging through all the treasures he has collected, and organizing the notes and letters he has written.
However, Darwin's words belie his actions. He amassed a large number of specimens from in and around the three areas he visited: Sydney, Hobart on the island of Tasmania, and King George's Sound in Western Australia. He also made some astute comments about Australian terrain. He noted that the extreme uniformity of the vegetation was the most obvious feature of most of New South Wales, where Sydney is situated. This was my experience as well, more than 150 years later. The sameness is attributable, in part, to the fact that most of the area is pastureland and has been since the early days of the colony. Grassland was everywhere, even as early as Darwin's visit. This helps to explain another of Darwin's comments: that a few years earlier the land was said to be rich in animals, but the emu was now rare and the kangaroo scarce. Darwin blamed English greyhounds for destroying them both, but habitat decimation was obviously involved as well.
Darwin also mentioned that he hardly saw a place that hadn't been marked by fire. This is still true today, both because fires are so frequent and because their effects are so long lasting. I was most aware of this when traveling up the coast of Western Australia. Since I was on a tour with botanically accomplished guides, I learned to read the landscape better than I ever would have on my own. These people visited the area frequently and knew its history, knew when fires had taken place. Some blazes were intentionally set to maintain the bush land, but many were triggered by lightning. It's dangerous to make any blanket statements about a country as large as Australia, but in general it is a dry place with poor soil, two facts that became painfully clear to British settlers as they tried to replicate English farms in the Southern Hemisphere. The fires are particularly prevalent in drought years, and Australia is just coming out of an 8-year dry spell; wild fires destroyed large expanses, some of them near settled areas.
The fire-scarred locales we visited in the west were primarily in uncultivated bush with few human settlements in the area. To give you an idea of the distances involved, we stopped for lunch in a small town and one of our number wanted to find a pharmacy. We were told that there was a drugstore in the next town. There was, but it was an hour and a half away. That's Western Australia. And this was near the coast; many areas in the interior are accessible only by dirt roads. What I am trying to get across is the idea that we traveled long distances, particularly through the large nature reserves in the west, through relatively undisturbed land, some of it former pastureland that has reverted to bush since it was added to a reserve. I have many photos of bush as far as the eye can see, but these pictures are disappointing because they fail to give a sense of the distances involved.
In one area, small, fire-charred, regenerating grass trees covered a large expanse. They belong to the genus Xanthorrhoea and regrow quickly after a fire, within a year or so, and then begin flowering again. So, in an otherwise barren landscape, there were these huge tufts of grass-like leaves, many with a single giant spike with tiny cream-colored flowers shooting up from the tuft's center. In areas with eucalypts, there can be badly burnt trees that have lush, leaf-covered shoots emerging from the deadest-looking branches. This is thanks to an adaptation that makes eucalypts capable of rapid regeneration after a fire. The shoots are called "epicormic buds," and in addition to them, lignotubers that grow from the roots also figure in the regeneration of eucalypts. These two adaptations are found in Banksia species as well. However, because it's so dry, there is little bacterial or fungal decay of dead trunks and branches, which can remain obvious in the bush even decades after a major fire, thus explaining why Darwin hardly saw an area that didn't have some evidence of fire.
In his book Darwin's Armada, Iain McCalman (2009) argues that it's more than just coincidence that Charles Darwin, Thomas Henry Huxley, Joseph Dalton Hooker, and Alfred Russel Wallace all undertook extensive ocean voyages, the latter two going on more than one such trek. The experiences these men had in seeing so much of the natural world when they were relatively young were pivotal in how their ideas about species developed in later years. I've already discussed Darwin's voyage from 1831 to 1836, which is obviously the most famous. But Thomas Henry Huxley also sailed around the world, as assistant surgeon on the Rattlesnake from 1846 to 1850. As the Beagle sailed into Sydney Harbor, so did the Rattlesnake, but this stop was more momentous for Huxley. It was there he met his future wife, Henrietta Heathorn, whom he married when she arrived in England in 1855. Huxley was not wealthy like Darwin, so when he returned to England he had to spend several years establishing himself before he could send for Henrietta. In the meantime, he busied himself with his work on jellyfish, which had also occupied much of his time while at sea. It was this work by which he made his name in zoology.
In his thorough biography of Huxley, Adrian Desmond (1997) stresses that Huxley's exposure to a variety of different ecosystems, geological formations, and cultures while traveling influenced his views on how climate, geology, and biota shaped species. Ray Desmond's (1999) biography of Joseph Hooker similarly emphasizes the importance of Hooker's travels, which were more extensive than those of his two friends and colleagues. First, he went on an expedition headed to Antarctica, visiting Australia on the way; stops included Hobart, Tasmania, and Sydney. Hooker spent enough time in the latter city to get to know the leading naturalists there, including the Macleays, whom I wrote about last month. The remainder of the voyage was less peaceful than the stops in Australia. The expedition had to make three attempts before finally making it to Antarctica, but this didn't dissuade Hooker from further travel. After the Antarctica trip, which lasted from 1839 to 1843, he set out on another 4-year expedition to India and the Himalayas; this is where he studied rhododendrons and collected specimens that were the basis for his book on the subject (Hooker, 1849).
The last member of the "Armada" spent the most time away from England. Like Huxley, Alfred Russel Wallace had to earn his own living, and he decided to do it while indulging his passion for the living world (Raby, 2001). His first major expedition was to South America with Henry Bates. Extending from 1848 to 1852, it was a harrowing trip that included a shipwreck in which Wallace lost all his specimens. However, just 18 months after he returned to England, he left again to spend almost 8 years in what is now Malaysia and Indonesia. Even though these areas are relatively close to Australia, he was the only one of the four never to set foot on that continent. However, he did visit New Guinea, and the eastern half of the island, known as Papua New Guinea, was for many years an Australian territory, though not at the time he was there.
I didn't get to the northern part of Australia, which is closest to New Guinea and is the most tropical. I obviously missed a lot in not going there, but I had great experiences in the areas I did see. One of my most memorable visits occurred while I was traveling in Western Australia. Our tour stopped to look at the stromatolites at Shark Bay. I had seen many pictures of these and similar structures in biology textbooks and in books on evolution. They are iconic because they are reminders of the very early stages of life on earth. To refresh my memory about them, and also learn more about the stromatolites of Western Australia, I bought a book by Ken McNamara (2009), who was curator of invertebrate paleontology at the Western Australian Museum in Perth. He explains how stromatolites form and then goes into the variations found at different sites in Western Australia.
McNamara notes that stromatolites develop differently in fresh than in salt water. It's the latter type that I saw in the bay, which is an inlet of the Pacific Ocean. However, earlier in the tour, we visited Lake Thetis, where the freshwater type grows. This lake is highly saline, but McNamara argues that it isn't the sodium chloride but rather calcium carbonate from groundwater discharged into the lake that creates the right environment for the growth of stromatolites. These are rather large whitish circles that can be seen beneath the water's surface. In many of them the center has caved in, and in general they are not as neatly formed as those in salt water that we saw a couple of days later.
A salt-water stromatolite begins with a microbial community rich in filamentous cyanobacteria that arrange themselves around grains of sand, trapping the sand in a biofilm. These organisms are then replaced by heterotrophs that form a mucilaginous sheet over the original layer of bacteria-encrusted sand. The next step involves sulfate-reducing bacteria that feed on the biofilm left by the cyanobacteria, leading to the growth of aragonite crystals (calcium carbonate) and the development of a crust. Finally, coccoid cyanobacteria colonize the surface. They bore into the calcium crust, forming minuscule tunnels that then fill with new crystal growth, which McNamara describes as "a sort of bacterial reinforced concrete" (p. 18). The sequence of colonizations is then repeated thousands of times to form the mounds that we call stromatolites. This may go on for hundreds or thousands of years. Cutting through a stromatolite is somewhat like cutting through a tree trunk and finding rings. The layering of microbes is evident and gives a history of countless cycles of these four bacterial interactions.
It's one thing to read a description of a stromatolite and it's another to see a beach edged with them. There are some that are totally submerged, and others are exposed during low tide. Still others are now permanently exposed to the air and are no longer developing. Stromatolites can grow to be about a foot thick, are loaf-shaped, and look like rocks. They might not seem very dramatic until you learn how they are formed and how long it takes for them to form. The stromatolite bed at Shark Bay is now a protected area, but wagons used to drive over these beaches in the 19th century and their tracks are still obvious – that's how slowly these structures grow.
The reason I found the stromatolites particularly intriguing, and why they are featured in books on evolution, is that they are thought to be similar to structures created by some of the earliest life forms on earth. It is in Western Australia that some of the best evidence for this idea is to be found, namely in the Pilbara, a large, sparsely settled region that is an important mining area. Iron ore is the major resource, and there are gold and other mineral mines as well. The area is so remote that the only reasonable access is by airplane. Yet despite its inaccessibility, its geology is well studied because of its rich mineral deposits. When people in the United States complain about big business, they are usually referring to banks, automobile makers, airlines, and various corporations. In Australia, the industry that is on everyone's lips is mining. It's the business Australians love to hate because of its environmental effects and political clout. Mining companies have put a lot of money into prospecting, and this has uncovered not only rich lodes but scientifically important geological features, such as stromatolites found in 3.43-million-year-old rocks. Some paleontologists are not willing to accept that these structures were made by bacteria and instead consider them the result of nonliving processes. However, a recent study of rocks that are 200 million years older and from a different location indicates that they contain the remains of sulfur-metabolizing bacteria; this adds support to the idea that the formations in the Pilbara are indeed stromatolites (Wacey et al., 2011).
I took more pictures at the stromatolite beach than anywhere else in Australia. This is probably not a good thing to admit, since I was on a botanical fieldtrip at the time and everyone else was using their high-powered lenses to capture each and every flowering plant they saw. Yes, those flowers were wonderful, and yes, many were unique to the area, but somehow the link the stromatolites have to the deep past was a bigger draw for me. I am partial to bacteria, so to see such visible and long-term evidence of their work was fascinating. I never did see a koala or a platypus or a kookaburra (though I heard one), but at least I saw a representative of a much more ancient life form, right there in its natural habitat. It's an indication of how much humans have changed the environment of Australia that even these bacteria need to be protected within a nature preserve.
Besides the stromatolites, I encountered many other reminders of evolutionary lessons on my trip. The most obvious one is the general strangeness of Australia's plants and animals to someone like me who has been stuck in the Northern Hemisphere my whole life. Being in Australia made me think about Pangaea and Gondwana in whole new ways. These formations, particularly the latter, came to seem more real to me. Pangaea, the term for the coalescence of all the continents, began to break up at the end of the Permian period. One of the fragments was called Gondwana and included Africa, South America, India, and Australia. These were all grouped around Antarctica, and this supercontinent began to fracture about 130 million years ago. Africa and South America broke off first, and around 120 million years ago India separated from Australia. The latter's break with Antarctica occurred approximately 80 million years ago. All of this happened before the evolution of placental mammals, making Australia very different from the rest of the world in terms of its fauna.
Watching a kangaroo run across a road at dawn, startled by an oncoming car, is a great reminder of convergent evolution. Yes, a kangaroo hops and doesn't run like a deer, but it has erect ears, a similar startle reflex, and the ability to get out of the way fast. They are both adapted to grasslands and scrublands, and have been shaped in similar ways by these environments. Both are also the bane of farmers, and, as Darwin noted, kangaroo populations were suffering from the effects of this even in the early 19th century.
As far as plants are concerned, some of the most diverse plant groups in Australia are the genera Acacia (family Fabaceae) and Banksia (Proteaceae) and eucalypts in the Myrtaceae. The bulk of the species in all three groups are endemic to Australia, another indication of its millions of years of isolation. The eucalypts are found only in Australia and in neighboring areas, particularly Indonesia. All the Banksia species are endemic, but Proteaceae are also found in South American and South Africa, remnants of the Gondwana connection. There are other reasons for these similarities between the floras of Australia and South Africa. They are both in the Southern Hemisphere and for many years were British colonies. Because British ships often stopped at one while on the way to the other, people, animals, and plants all ended up moving back and forth. The South African climate is also similar to that of southern Australia, so that also accounts for the fact that many of the same plants flourished in both areas. Proteaceae are amazing flowers and I couldn't get enough of them. Sure I could buy them from a New York florist, but that's nothing like seeing them grow wild among fire-scarred branches and rocky terrain.
My major reason for going to Australia was to attend the International Botanical Congress in Melbourne. I heard many great lectures, but the best fun was at the end of the conference, when the resolutions that govern botanical classification were approved. There were three rather contentious ones. The first involved no longer requiring a Latin description of a new species. This passed, but not without some references to botany being the last bastion of the language. Another dealt with allowing electronic publication of new species; this was also contested, which seems odd given that this resolution might lead to the destruction of fewer trees. Finally, and perhaps most seriously for systematists, there was a resolution about the naming of Acacia species.
I had heard about this issue before I left, but because of my lack of botanical knowledge I hadn't realized its significance until I landed in Sydney and visited the Royal Botanic Garden. There I saw a wattle, a member of this genus, in bloom. Its label referred to the importance of acacias to Australians; one species in the genus (Acacia pycnantha) is Australia's national flower (Anonymous, 2011), and there are a thousand endemic species in Australia. However, thanks to Gondwana, there are also acacia species native to South America and to Africa. If the wattle is an Australian icon, the acacia tree is an African one. DNA sequencing has shown that these two groups should not be in the same genus, but the question then becomes, if some are pulled out, which ones get to keep the genus name? There is a rule in botany for this: the name goes with the species that is the type for the genus. In this case, the genus type is an African species (Acacia nilotica) named by Carl Linnaeus; therefore, "legally" the African species should get to keep the name. However, there are only 80 African species and a thousand Australian ones, leading to a renaming nightmare. At the last botanical congress, in 2005, a resolution was approved to give the name to the Australian species. This did not sit well with everyone, so the issue was brought up again, and again decided in favor of the Australians – if they "won" in Vienna, they were a shoe-in in Melbourne. The African acacias will be put into a new genus called Vachellia. That presumably will be the end of the matter, and it definitely is the end of my account of my trip to Australia.