The accident chaser


Some people get their kicks out of chasing ambulances to the scenes of collisions. Elizabeth (Lizzy) Joyce is on the trail of one of the biggest collisions of all time, the spectacular 30 million year slow crash of Australia into south-east Asia.


Lizzy grew up in Perth, a daughter of a geologist and an engineer. As is often the case, she decided not to make a career in either geology or engineering. A skilled artist, she considered a Fine Arts degree at university, but an interest in the natural world led her to a science degree at the University of Western Australia.


A turning point in her career came during a single lecture, in a second-year unit on plant diversity and evolution.


Her lecturer, Ryonen Butcher from the Western Australian Herbarium, described the research life of a taxonomist, enthusing in particular about recent field work to solve a taxonomic puzzle in one of her study groups.


Now Lizzy had always wanted to be an explorer, but assumed that exploring was a thing of the past. Ryonen's lecture that day convinced her this was not the case, and that taxonomists are modern-day explorers.


Lizzy's own explorations began with an Honours project studying a group of potentially new species in the plant genus Tetratheca in Western Australia. Tetratheca is an attractive genus of small shrubs with four- or five-petaled, showy flowers. Several species are extremely rare, growing only in cracks in cliffs in remote, arid ranges in the south-west and Pilbara. Understanding the taxonomy of plants like Tetratheca is critically important for their conservation, especially in the face of mining projects where these rare species occur.


A first foray into exploration: collecting tetrathecas for her Honours project. Photo (c) Ryonen Butcher

Lizzy's Honours project resolved the difficult taxonomy of the last remaining species complex in the genus, and resulted in her describing and naming two new, rare subspecies of Tetratheca hirsuta.


With her first experience of taxonomic research complete, Lizzy moved to the Australian Tropical Herbarium in Cairns to tackle a PhD on a much larger problem - colliding continents


Two hundred million years ago the Earth had two very large supercontinents, Gondwana and Laurasia. Each had a rich complement of plants, dinosaurs, early mammals, insects, fish and all the other groups of organisms we're familiar with today.


Beginning around 180 million years ago, the southern supercontinent Gondwana began to split apart, eventually separating into South America, Africa, Madagascar, India, Australia, New Zealand and Antarctica. Each of these (except Antarctica) began to drift northwards, carried by giant convection currents in the Earth's mantle. This northward drift eventually resulted in some of them crashing into the northern continents derived from Laurasia. South America fused with North America, Africa with Europe, and India with south Asia.


Lizzy is seeking to understand the implications for our biodiversity of the last great collision, one that we're still in the middle of today - the collision of Australia with south-east Asia.


The collision of two great biogeographic regions. Shaded areas represent dry land when low sea levels during glaciations create two great landmasses, called Sunda and Sahul. Image by Maximilian Dörrbecker (Chumwa) CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=7382691.

Of course, Australia and Asia have not yet actually joined together (over time they will). Instead, they're approaching ever closer, creating as they do so one of the most geologically complex regions on Earth, the island chains of Indonesia, Papua New Guinea and the Philippines.


And this has allowed plants and animals with very different evolutionary histories to mingle for the first time, island-hopping through the archipelagoes and enriching each side with new diversity. Lizzy is studying some of the plant groups that have dispersed in both directions, to understand more about when, how and why they dispersed, and the implications of the changes that have occurred in the region, including the spectacular uplift of the Papua New Guinea Highlands, on speciation and evolution.


Lizzy always wanted to be an explorer. In working to understand the history of our biodiversity through this collision, she's following in some ways in the footsteps of one of the world's greatest 19th Century explorers, the naturalist Alfred Russell Wallace. Wallace, who independently from Darwin developed the theory of evolution by natural selection, also wondered at the biodiversity of the region while collecting plants and animals there between 1854 and 1862. He attempted to explain the evolution of today's patterns of biodiversity, explanations that Lizzy is helping test. Wallace is honoured in the region today by Wallace's Line, perhaps one of the most famous biogeographical boundaries, and the informal name Wallacea for the area between Australia and Asia.


Alfred Russell Wallace in 1896. Image: By London Stereoscopic & Photographic Company (active 1855-1922) - First published in Borderland Magazine, April 1896, Public Domain, https://commons.wikimedia.org/w/index.php?curid=27755581

The questions Lizzy is attempting to answer are devilishly tricky, but they go to the heart of some big questions - evolution, speciation, adaptation,and extinction of biodiversity during a grand sweep of Earth's history. This one is a collision worth chasing.


A break during field work in the Kimberley, collecting specimens of Aglaia to understand patterns of connection between Sunda and Sahul. Photo (c) Ryonen Butcher

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