Biology and Biologists
Flowering Eucalypt, photographed in 1920 (AOT,
The histories of Tasmania's biology and biologists reflect both the island's isolation and its past connections with other parts of the world. A few animals and plants are remnants from 200 million years ago when the world's continents were joined to form the supercontinent Pangea. These include cave spiders, freshwater crayfish, the mountain shrimp (Anaspides) and perhaps the mountain pines (Athrotaxis). However, many more Tasmanian plants and animals have histories linked to Gondwana. 150 million years ago this giant fragment of Pangea contained all the major modern landmasses of the southern hemisphere, but has been breaking up ever since. Tasmania's last land connection with Antarctica was about 50 million years ago.
In spite of enormous ocean distances, most of the flora and fauna have close relatives in other fragments of Gondwana (New Zealand, South America, New Caledonia or South Africa). This could mean that their ancestors were in Gondwana and were split into different populations when Gondwana broke up. Alternatively, the ancestors of some modern species may have crossed oceans afterwards.
Plant fossils (including pollen, spores, leaves and fruit) clearly show that many groups of Tasmanian plants, especially rainforest plants and some other trees and shrubs, were in Gondwana. These include Myrtaceae (the eucalypt and tea-tree family), Proteaceae (the Banksia, grevillea and waratah family), Nothofagus (the southern beeches), Eucryphia (leatherwood) and the southern conifers. In contrast, the available evidence suggests that the southern connections of most herbs are more recent.
Unfortunately, fossils of land animals are rare, and uninformative about Gondwanan heritage. However, monotremes, marsupials, tree frogs and many invertebrates were probably derived from the ancient Gondwana fauna. Some other groups, such as rodents and bats, came from south-eastern Asia after Australia collided with that region 15 million years ago.
Another link is with mainland Australia. Tasmania shares most of its biota with south-eastern Australia. Tasmania became an island about 23 million years ago, but has been joined to the mainland whenever sea levels were low. This occurred many times over the last two million years, most recently until about 10,500 years ago. These intermittent connections allowed some invasion from mainland Australia. However, much of the biota is unique to the island, partly due to distinctive environments, such as alpine and rainforest areas in the south-west. Some endemic species are relics of more widespread distributions in the past; others have arisen through differentiation of Tasmanian populations from mainland relatives during periods of isolation. Over 320 of the more than 1600 flowering plants native to the island are endemic. They include 17 of the 29 eucalypt species. Of the island's native mammals (two monotremes, 19 marsupials, 14 rodents and bats), two species and six subspecies are endemic. Three of Tasmania's 21 reptiles, three of the 11 amphibians and 17 of the 44 native freshwater fish are endemic.
Regardless of where the ancestors of our modern species came from, massive environmental changes have moulded the flora and fauna. Since about 55 million years ago, when Tasmania connected Australia to Antarctica, the climate has become cooler and much drier. These changes involved quite abrupt steps, and several reversals, and resulted in massive extinctions and extensive evolution of Gondwanan lineages and recently arrived groups. The widespread, diverse rainforest was largely replaced by open forests and woodlands that now dominate the island. This climatic deterioration culminated in the cycles of ice ages of the last two million years, with long periods of cold and sometimes very dry climates. Although some species thrived in these conditions, some (such as the unique eucalypts of south-eastern Tasmania) only survived in small refugia and others recolonised by dispersal from other regions.
The arrival of humans about 40,000 years ago had a major impact on the biota, through fire and hunting of large marsupials and birds. In spite of this, isolation over the last 10,500 years allowed once widespread species such as Tasmanian devils, thylacines and native hens to persist in Tasmania. Agriculture, forestry, mining, fishing and introductions of exotic plants and animals over the last 200 years had perhaps an even greater impact. At least 24 plant species and eight animals (including Thylacines, King Island Dwarf Emus and Tasmanian Emus) became extinct. Tasmanian estuaries have been particularly affected, with exotic algae and invertebrates becoming more common and diverse. However, isolation has buffered several smaller marsupials and vegetation from the effects of foxes, pigs and goats.
Before European settlement the most detailed biological exploration was by French scientists such as botanist Jacques-Julien Houtou de Labillardière (d'Entrecasteaux Expedition 1792–93) and zoologist François Péron (Baudin Expendition1801–03). With the arrival of the first settlers in 1803 came the Scottish botanist, Robert Brown, who published his landmark Prodromus florae Novae Hollandiae et insulae Van Diemen in 1810. Through the efforts of local collectors such as Ronald Gunn, Robert Lawrence, Joseph Milligan and William Archer, Sir Joseph Hooker, the director of Kew Gardens in England, produced the Flora Tasmaniae in 1859. This flora was followed by Leonard Rodway's The Tasmanian flora (1903) and later Winifred Curtis' The student flora of Tasmania (1956), which, in its revised form, is still used today.
Notable zoologists of this early era included William Saville-Kent, who was involved with the introduction of European oyster culture techniques and described many new species of fish; and Arthur Lea, a foundation member of Tasmanian Field Naturalist Club, who described 4500 new species of beetles. A major impetus for biological research in Tasmania came with the establishment of the Royal Society of Tasmania in 1843. The founding of the University of Tasmania in 1890 and the commencement of its Department of Biology followed in 1909. The lecturer and subsequent Professor was Theodore Thomson Flynn, whose son was Errol of Hollywood fame. Vernon Hickman, who was internationally recognised for his work on Tasmanian spiders, followed him. The first Professor of Botany, Horace Newton Barber, was appointed in 1947. He was a geneticist, internationally known for his work on peas and the Tasmanian eucalypts. This specialisation in eucalypts is still seen today, as two consecutive Cooperative Research Centres in forestry have had their headquarters in Hobart since 1991. The current marine expertise in Tasmania is relatively recent; the Antarctic Division moved from Melbourne to Hobart in 1981 and CSIRO Marine Research moved from Sydney in 1984.
Further reading: R Hill et al, 'Evolution of the Australian flora: fossil evidence', Flora of Australia 1, Canberra, 1999; B Potts & J Reid, 'Tasmania's eucalypts', PPRST 137, 2003; State of the Environment Unit, State of the Environment Tasmania 1, Hobart, 1996; Resource Planning and Development Commission, State of the environment Tasmania 2003, Hobart, 2003; www.rpdc.tas.gov.au/soer.
Brad Potts and Greg Jordan