Kauri pines are late-blooming rainforest giants



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Michael Yuen/Flickr, CC BY-NC

Kevin Glencross, Southern Cross University

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When I first came across the kauri pine (Agathis robusta), I certainly wasn’t impressed by their growth. Mixed among other species in a young rainforest plantation, they seemed destined to be left behind by the faster-growing trees (I did think they looked nice, though).

But today I know I judged the kauri unfairly. They can survive for millennia, so they don’t bother doing all their growing in their first couple of decades. But come back 20 years later, and that unassuming tree will be well on its way to being one of the giants of the forest.




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The Conversation

Impressive by any measure

By any yardstick, kauri pines are truly unique and impressive. If time is our measure, then the kauri family, Agathis, has endured over epochs, with fossils found in Australia from the early to mid-Jurassic period. Having withstood the rise and fall of the dinosaurs and the evolution and diversification of our flora, 17 species of living fossil trees in the Agathis family remain.

Agathis is an iconic genus of large, ecologically important, and economically valuable conifers that now range over lowland to upper montane rainforests from New Zealand to Sumatra. So, if we judge a plant’s success in terms of its geographical spread or its ability to adapt to a range of conditions, the Kauri family is once again outstanding.

If we measure a plant by appearances, then the tall, robust and handsome Queensland kauri pine remains an impressive – albeit little-known – plant. Reaching up to 50 metres, it emerges above rainforest margins in tropical and subtropical eastern Australia. Its straight, round trunk can grow to 3m in diameter and a combination of smooth mottled bark, coppery new growth and dark green canopy make this tree a world-class ornamental. In parks and gardens across Australia, Kauri pine cuts a fine figure, growing to enormous sizes, even in southern regions.




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Our Australian kauri pine, once common in the dry rainforests of Queensland, has become a victim of its own success. A heavy reliance on the highly regarded wood during the earliest stages of the colonial timber industry has left only a few old trees standing, mostly in remote areas or forest reserves. In my role as a research scientist, I have tracked down the kauri’s cousins in the Pacific regions, where the giant pines can now only be found on tops of mountains on remote islands. In New Zealand, the giant kauri that once covered large areas are in danger from the soil-based fungus Phytophora.

Germaine Greer, in her 2014 book White Beech, describes visiting a massive kauri tree on the North Island over 50m tall and 13.5m in girth that is in danger of succumbing to the fungus after a life measured in millennia.

A useful tree

According to the Gymnosperm Database, Queensland kauri was first reported by Europeans in 1842 by Andrew Petrie, who found it growing in the Mary River country, and reported that the native peoples made their nets from its inner bark. A fine, even texture set this timber apart from the more common Hoop pine.

In the South Pacific, the cousins of the Australian kauri have a strong cultural significance and features in the Maori creation myth. The wood from the Southern Kauri (Agathis australis) was used for water craft, and the gum used in traditional tattoos (moko).

Enthusiastic attempts by the Queensland Forest Service to grow the kauri in plantations were devastated by large stick insects. As a result, kauris are now only grown at a very small scale in mixed species rainforest timber plantations, which is where I stumbled upon them.




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In about 2002, during my PhD study of young (8-15 years old) rainforest plantations, I first measured kauri as a small tree amongst the well-regarded cabinet timber species of mahoganies and white beech. At first glance, the appeal for me of this Jurassic fossil was merely aesthetic. They were not very impressive in terms of early growth in the plantations; so I focused my attention on the rapid, early growing species.

However, having ignored the kauri for about 10 years, I was astonished (upon return to my old study sites) at how rapidly the kauris had progressed. Not only is this species one of the best performers in terms of diameter growth, but it also has excellent form. It produces straight stems free of large branches that indicates excellent quality logs, for those growers who value wood quality.

My regard for the kauri is now much more than aesthetic; or even as quirky relics from deep time. These trees are showing themselves to be extremely resilient and competitive, under challenging climatic conditions, across a very wide range of sites. They have the capacity to withstand severe storms as well as longer term stresses, such as drought.

I now know that, given the kauri pine can live for many centuries, it is not advisable to measure their value according to the first decade or so of growth, but rather their productivity and resilience across their whole lifespan.




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Sign up to Beating Around the Bush, a series that profiles native plants: part gardening column, part dispatches from country, entirely Australian.. Read previous instalments here.

This article was updated on Tuesday March 12 to correct an error. It previously stated a tree encountered by Germaine Greer was 13.5m in diameter; in fact the tree was 13.5m in girth.The Conversation

Kevin Glencross, Research Fellow, Southern Cross University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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How birds become male or female, and occasionally both


Jenny Graves, La Trobe University

The highly unusual “semi-identical” Australian twins reported last week are the result of a rare event. It’s thought the brother and sister (who have identical genes from their mother but not their father) developed from an egg fertilised by two different sperm at the same moment.

In humans, it’s the sperm that determines whether an embryo is pushed along a male or female development pathway. But in birds, it’s the other way around. Eggs are the deciding factor in bird sex.




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There are other fascinating aspects of bird sex that are not shared with humans. Female birds seem to have some capacity to control the sex of their chicks. And occasionally a bird that is female on one side and male on the other is produced – as in recent reports of this cardinal in the United States.

A half-male, half-female cardinal was recently spotted in Pennsylvania.

X and Y, Z and W chromosomes

So what is it about bird chromosomes that makes bird sex so different from human sex?

In humans, cells in females have two copies of a large, gene-rich chromosome called X. Male cells have one X, and a tiny Y chromosome.




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Birds also have sex chromosomes, but they act in completely the opposite way. Male birds have two copies of a large, gene-rich chromosome called Z, and females have a single Z and a W chromosome. The tiny W chromosome is all that is left of an original Z, which degenerated over time, much like the human Y.

When cells in the bird ovary undergo the special kind of division (called “meiosis”) that produces eggs with just one set of chromosomes, each egg cell receives either a Z or a W.

Fertilisation with a sperm (all of which bear a Z) produces ZZ male or ZW female chicks.

Birds can control the sex of their chicks

We would expect that, during meiosis, random separation of Z and W should result in half the chicks being male and half female, but birds are tricky. Somehow the female is able to manipulate whether the Z or W chromosome gets into an egg.

Most bird species produce more males than females on average. Some birds, such as kestrels, produce different sex ratios at different times of the year and others respond to environmental conditions or the female’s body condition. For example, when times are tough for zebra finches, more females are produced. Some birds, such as the kookaburra, contrive usually to hatch a male chick first, then a female one.




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Why would a bird manipulate the sex of her chicks? We think she is optimising the likelihood of her offspring mating and rearing young (so ensuring the continuation of her genes into future generations).

It makes sense for females in poor condition to hatch more female chicks, because weak male chicks are unlikely to surmount the rigours of courtship and reproduction.

How does the female do it? There is some evidence she can bias the sex ratio by controlling hormones, particularly progesterone.

How male and female birds develop

In humans, we know it’s a gene on the Y chromosome called SRY that kickstarts the development of a testis in the embryo. The embryonic testis makes testosterone, and testosterone pushes the development of male characteristics like genitals, hair and voice.

But in birds a completely different gene (called DMRT1) on the Z but not the W seems to determine sex of an embryo.

In a ZZ embryo, the two copies of DMRT1 induce a ridge of cells (the gonad precursor) to develop into a testis, which produces testosterone; a male bird develops. In a ZW female embryo, the single copy of DMRT1 permits the gonad to develop into an ovary, which makes estrogen and other related hormones; a female bird results.

This kind of sex determination is known as “gene dosage”.

It’s the difference in the number of sex genes that determines sex. Surprisingly, this mechanism is more common in vertebrates than the familiar mammalian system (in which the presence or absence of a Y chromosome bearing the SRY gene determines sex).

Unlike mammals, we never see birds with differences in Z and W chromosome number; there seems to be no bird equivalent to XO women with just a single X chromosome, and men with XXY chromosomes. It may be that such changes are lethal in birds.

Birds that are half-male, half-female

Very occasionally a bird is found with one side male, the other female. The recently sighted cardinal has red male plumage on the right, and beige (female) feathers on the left.

One famous chicken is male on the right and female on the left, with spectacular differences in plumage, comb and fatness.

The most likely origin of such rare mixed animals (called “chimaeras”) is from fusion of separate ZZ and ZW embryos, or from double fertilisation of an abnormal ZW egg.

But why is there such clear 50:50 physical demarcation in half-and-half birds? The protein produced by the sex determining gene DMRT1, as well as sex hormones, travels around the body in the blood so should affect both sides.




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There must be another biological pathway, something else on sex chromosomes that fixes sex in the two sides of the body and interprets the same genetic and hormone signals differently.

What genes specify sex differences birds?

Birds may show spectacular sex differences in appearance (such as size, plumage, colour) and behaviour (such as singing). Think of the peacock’s splendid tail, much admired by drab peahens.

You might think the Z chromosome would be a good place for exorbitant male colour genes, and that the W would be a handy place for egg genes. But the W chromosome seems to have no specifically female genes.

Studies of the whole peacock genome show that the genes responsible for the spectacular tail feathers are scattered all over the genome. So they are probably regulated by male and female hormones, and only indirectly the result of sex chromosomes.The Conversation

Jenny Graves, Distinguished Professor of Genetics, La Trobe University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Welcome Asterix, Obelix and Yoda! Finding fun in the serious matter of discovering insects



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Do these look like Gauls to you? Three of the 103 new weevils identified in Indonesia were named after characters Asterix, Obelix and Idefix.
Alexander Riedel

Nick Porch, Deakin University

Forget the apes, we live on “The Planet of the Beetles”. Welcome.

With an estimated 387,000 formally described species, beetles (Coleoptera) are the most species-rich of the five mega-diverse groups of insects. The others are wasps, ants and bees (Hymenoptera), flies (Diptera), true bugs (Hemiptera), and butterflies and moths (Lepidoptera).




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Today’s publication of 103 new species of weevils from the Indonesian island of Sulawesi is a timely reminder that, after several hundred years of research, we have not even described half of the insect diversity out there. Not even close. Especially in the tropics.

This seems particularly important in light of recent media attention on the global loss of insects (which may or not be an “insectageddon”, depending on how you look at the data).

Knowing what we have

Ideally, before we worry about what we are losing, it would be nice to know what we have.

Guesstimates of the number of beetle species on Earth suggest that only about one quarter of the species out there have been described.

Although most British species were described by the middle of the 19th century, in many parts of the world it is easy to find new species and will be for many decades, providing they hang on that long.




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And it’s probably best to set aside the notion of cracking a bottle of champagne with every new species discovery. As writer Simon Barnes says, referring — in Ten Million Aliens: A Journey Through the Entire Animal Kingdom — to people who discover new species, “they’d be pissed all day”. If you work on weevils, you’d be comatose.

Welcome weevils

Alexander Riedel, a weevil specialist from Germany, and Indonesian museum curator Raden Pramesa Narakusumo are working on the Asia-Pacific weevil genus Trigonopterus.

These small weevils, mostly several millimetres long, are distributed from Samoa in the Pacific through northern Australia to Sumatra. Australian Trigonopterus (32 described species) are mainly restricted to subtropical and tropical rainforests of the east coast, north from around the Queensland/New South Wales border.

The authors’ latest paper describes 103 new species from Sulawesi (Celebes of old) including several they named after Asterix, Obelix and Idefix – principal characters in the French comic series The Adventures of Asterix.

Asterix and Obelix don’t like the Romans much.

Species names are always lower-case and the genus always begins with a capital: for example “Trigonopterus asterix Riedel”, named after Asterix. Italics are used to show that we are talking about a genus and/or species name. The author or authors primarily responsible for describing the species are traditionally appended to the end of the name.

A small greenish forest-dwelling species is named after Yoda of Star Wars fame, and several others after well-known biologists including Charles Darwin, James Watson and Francis Crick (the latter two identified the structure of DNA).

103 new weevil species from Sulawesi: can you pick the differences between them all?
Alexander Riedel

Naming is fun but hard

Naming species in novel ways is more common that you might think. Just this week one of 14 new northern Australian dung beetle species was named Lepanus sauroni Gunter & Weir, after, you guessed it, Sauron of Lord of the Rings fame. Part of the beetle’s abdomen resembles the Eye of Sauron.

Most of the new Trigonopterus (and Lepanus) species are named after the locality where they were discovered, their collector, or distinctive characters they might have.




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You might imagine coming up with 103 new names would be relatively easy, but it’s not that simple. There were already 341 Trigonopterus described (mostly by Riedel and colleagues), and the new names have to be different. The names for new species of this genus described in the future, and there are hundreds more, will have to be different again.

Living in Melbourne, as I do, there are plenty of undescribed invertebrate species including, of course, weevils. If you know what you are doing, many of these are abundant and easy to find. Some may represent charismatic, colourful, fascinating or old evolutionary lineages. Many of these species are known and are preserved in national or international collections awaiting description, but plenty of others are unseen and uncollected.

Who cares? And why?

A widespread lack of enthusiasm for invertebrates translates to a broader lack of knowledge and engagement, and the inevitable “who cares anyway?”.

In Wonderful Life, author Stephen Jay Gould writes:

Classifications are theories about the basis of natural order, not dull catalogues compiled only to avoid chaos.

Describing species, and revealing what is where, fundamentally underlies major fields of biology like ecology, evolution and biogeography, contributing to a deeper understanding of the complexity of life on Earth.

If we’re to prevent the loss of major parts of our biodiversity to extinction, a deeper understanding of the planet’s numerically dominant invertebrate life is critical. Fortunately, there are those like the authors of these papers who follow their passion, and back it up with a lot of highly skilled work.The Conversation

Nick Porch, Senior Lecturer in Environmental Earth Science, Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.