What are the origins of Western Australia’s iconic boab tree, whose only living relatives survive far away in Africa?
AUSTRALIA ISN’T KNOWN for its deciduous trees. Across vast swathes of forest on other continents, the annual cycle of shedding and regrowth is ubiquitous. Each year, as days shorten and temperatures drop, leaves fall. Trees shut down for winter, biding their time before embarking on a huge spring growth spurt.
But in Australia’s highly variable boom-bust climatic conditions, the evolutionary path to deciduousness was never really an option. Putting on leaves in response to seasonal change, only to have that foliage wither prematurely during tough times, is biologically wasteful. Unable to rely on predictable seasonal cycles, our trees have become opportunists, waiting out dry spells by tapping groundwater, their permanent leaf canopy always at the ready in case rain does come. The omnipresent eucalypts are a perfect example of Australia’s ascendant evergreens.
Although evergreens are ecologically triumphant here, Australia is home to a small number of native deciduous tree species. All but one are restricted to tropical or subtropical environments; the outlier is the deciduous beech of Tasmania’s cool-temperate mountains, a glorious autumnal relic of the supercontinent of Gondwana.
Australia’s other deciduous trees lose some or all of their leaves not in readiness for the winter cold, but to best survive the northern dry season. Species include the red cedar and that spectacular red-flowered endemic the Illawarra flame tree.
The red cedar is also found in Asia, and Australia serves as the regional genetic hotspot of the Illawarra flame genus, Brachychiton. But there is one remarkable Australian deciduous tree that doesn’t have a single native sibling, nor any presence elsewhere in our region. That total loner is the unmistakable boab of Western Australia’s Kimberley region.
この記事は Australian Geographic Magazine の May - June 2019 版に掲載されています。
7 日間の Magzter GOLD 無料トライアルを開始して、何千もの厳選されたプレミアム ストーリー、9,000 以上の雑誌や新聞にアクセスしてください。
すでに購読者です ? サインイン
この記事は Australian Geographic Magazine の May - June 2019 版に掲載されています。
7 日間の Magzter GOLD 無料トライアルを開始して、何千もの厳選されたプレミアム ストーリー、9,000 以上の雑誌や新聞にアクセスしてください。
すでに購読者です? サインイン
Loveday Internment Camp, SA A
DURING WORLD WAR II, civilians n Australia deemed \"enemy aliens\" - mostly those of German, Italian and Japanese descent were housed in internment camps.
THE STORYTELLERS OF THE GREAT BARRIER REEF
More than 100 dedicated Master Reef Guides are sharing the GBR's most important stories with visitors in a bid to inspire its greater protection.
A BEAUTIFUL DISASTER
Does last summer's mass coral bleaching event sound a death knell for Australia's beloved Great Barrier Reef? \"Not on my watch!\" is the message coming from he army of heartbroken, but resolute, marine scientists who've responded to the crisis by doubling down on their research.
AROUND AUSTRALIA IN 44 DAYS
This year marks the 100th anniversary of the first aerial circumnavigation of Australia. Aviator Michael Smith retraces the flight in his unique amphibious flying boat, Southern Sun, starting and finishing at RAAF Base Point Cook, on Melbourne's Port Phillip, taking in 15,000km of vast, diverse and stunning coastline in between.
CLEAR-CUTTING KOALA COUNTRY
More than 3000sq.km of forests on NSW's Mid North Coast have been earmarked for the Great Koala National Park. But there's still work to be done before this proposed reserve becomes the safe haven koalas desperately need.
MORE THAN QUOKKAS
Sure, you can't avoid those cute little marsupials that made Rottnest Island world-famous, but there's so much more to life on this ocean-ringed jewel off the Western Australian coast.
A WILD POLO TUSSLE
It's an event reminiscent of a Banjo Paterson poem. For 35 years, in the High Country 200km east of Melbourne, city polo players have gathered annually at Cobungra, Victoria's largest cattle station, to vie with a rural team for the Dinner Plain Polo Cup.
Ancient know-how meets a modern challenge
Contemporary marine park management is infused with traditional knowledge to tackle new threats on the Great Barrier Reef.
LOOKING FOR TJAKURA
The search is on across Australia's deserts for a culturally important vulnerable lizard.
RESCUING THE CHUDITCH
After intensive planning, recovery for this endangered marsupial species is being stepped up to secure its future.