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Photos from the field: East Gippsland, Victoria

I recently began a brand new project with the University of Melbourne. The beginning of a new project is filled with equal parts excitement and trepidation—excitement at the novelty, the blank canvas, the potential, and trepidation at not wanting to put a foot wrong in critical early decisions that will affect the outcome of a career-defining opportunity.

Here the photos from a first foray into East Gippsland, surveying sites for bird-pollinated Prostanthera walteri.

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Mt. Elizabeth

 

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Snowy River National Park

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Prostanthera walteri

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Prostanthera hirtula

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McKillops Bridge

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The Snowy River

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The Snowy River

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Prostanthera walteri

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Snowy River National Park

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Gippsland waratah – Telopea oreades

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Floral diversity in Prostanthera

 

Australia’s sexual swindlers.

Seduction. Pollination. Deception.

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I recently wrote an article for Wildlife Australia about Australian sexually deceptive orchids, their evolutionary biology, and historical and current research about them. You can download and read the article here: PDF. Thanks to Carol Booth for her collaboration and editorial guidance.

The latest of Australia’s sexually deceptive orchids that I have seen (below) are Caleana major, the Flying Duck orchid (left), and a spider orchid Caladenia clavigera (right). Both were photographed last week in Brisbane Ranges NP, Victoria.

Flowering this year is one of the best seasons of recent times both east and west of the country. So if you’re in Australia, don’t miss the chance to get out bush and enjoy it.

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Sex, lies and pollination. Australia’s remarkable sexual swindlers.

Article reposted from original publication with The Territories.

Rather than luring its pollinator with the promise of food this flower uses an equally, if not more, powerful motivator: sex.

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In shades of dusky green and claret red, the bird orchid’s subdued palette hints at its alternative lifestyle. The usual strategy for flowers attempting to catch the compound eye of a passing insect is to advertise proudly. Petals are used as panels for saturated colour, assembled en masse into conspicuous aggregate displays exuding exotic scents. In this way, nectar-filled flowers loudly broadcast the promise of their reward to entice would be pollinators into servicing them.

 

A deviant among flowering plants, the bird orchid eschews these typical hallmarks of floral advertisement. Crouched modestly on the forest floors of eastern Australia, its stature belies its status as one of the supreme specialists amongst the world’s flowering plants. Like those other showy flowers, the bird orchid needs the service of a pollinator from time to time, however unlike most other flowers, it attracts its pollinator without the payment of any reward. The orchid flower in fact completely lacks nectar.

 

Rather than luring its pollinator with the promise of food this flower uses an equally, if not more, powerful motivator: sex. Undetectable to human senses, the orchid’s advertisement is a precise chemical mimicry of a female wasp’s sex pheromone. This is targeted marketing at its finest, as the use of a signature sex pheromone ensures that the orchid attracts only males of a specific species of wasp.

 

Skimming by on wide zig-zagging flights, the wasps are interminably attracted when the ruse takes hold. They alight onto the flower with fervor, probing and hunting for the mate that their senses scream must be there. Bucking back into the column of the flower (the reproductive parts of an orchid flower are fused in this special structure), they make contact with the anthers and a large packet of pollen is deposited on them. The wasp disengages eventually and leaves, but soon, elsewhere, he will catch on the breeze the smell of a mate, and if fooled again, fulfill his role as duped courier for an orchid’s reproductive ends.

 

Called “sexual deception”, this mode of pollination was noticed by Darwin and his contemporaries in an age in which Europe’s natural sciences were in full bloom. It was a naturalist in Blackburn, Victoria however, who was first to discover the phenomenon outside Europe. In 1927, Edith Coleman had turned her great capacity for observation of the natural world to a peculiar native orchid. Resembling more flesh than flower, Cryptostylis, known also as “tongue-orchids” had caught her attention for its magnetic allure to a specific kind of wasp. Through her observations, Coleman was able to discern that male wasps were being attracted to the flower in order to copulate with it. An experiment through a window showed scent to be the primary attractant, and Coleman even observed the ejaculate remaining after having been visited by clearly convinced wasps. She wrote up her notes in a series of papers for the Victorian Naturalist and Transactions of the Royal Society for Entomology, which made quite a splash with the best of botany at the time.

 

We now know this was the tip of the iceberg. Australia is not only home to tongue orchids, but hosts a diverse array of other sexually deceptive orchids including the spider orchids, elbow orchids, hammer orchids, dragon orchids, greenhoods, duck orchids, hare orchids, beard orchids, bird orchids, and the list goes on. Harbouring over 50% of the world’s known examples of sexually deceptive pollination, Australia is certainly the world’s hotspot for this unusual phenomenon. Remarkably, we have several hundred species that employ this unique brand of pollinator attraction, and what is more remarkable, the evidence points to at least six different independent evolutionary occurrences in the Australian orchid family tree. To our eyes, sexual deception seems like a freaky, unlikely strategy and its repeated independent incidence through Australia’s evolutionary history is therefore a startling paradox.

 

Although the reliance on a single species of pollinator for pollination seems precarious, studies have demonstrated that sexual deception comes with the advantage of promoting healthy breeding for our native orchids. In nectar-bearing plants, foraging insects will frequently move between flowers on the same plant and between neighbouring plants. Called “optimal foraging”, exhausting local nectar supplies in a patch before putting energy into finding a new buffet makes economic sense for a nectar-feeding insect. Sexual deception however, has been shown to drive pollinators far from the flower after being fooled, so that pollen escapes the local neighbourhood. As a plant, your neighbours are likely to be related to you, thus deception is a way of ensuring offspring quality by avoiding breeding with your relatives.

 

Another factor supporting the profusion of our sexually deceptive species is Australia’s immense diversity of insects to fool. Although there are examples of gnat and ant sexual deception systems, wasps are the most commonly targeted pollinator for our orchids. Incredibly, we are only now beginning to uncover the immense hidden diversity of Australian wasps. For example, a recent study in a small patch of bush near Margaret River uncovered 28 species of wasps, most of which were previously unknown to science. With each of these species most likely having their own private sex-pheromone cocktail, there is seemingly a kaleidoscope of chemical communication channels available for different orchids to exploit.

 

Despite our deepening understanding of the natural history of sexual deception, its repeated occurrence in Australia remains a true puzzle.

 

Try the Atlas of Living Australia’s region search to discover which orchids (Plant family: Orchidaceae) live near you. [Link: http://biocache.ala.org.au/explore/your-area%5D

New article: The Territories

The Territories is Heath Killen’s new project. The site blends stories of Australia’s natural and cultural history under a unique aesthetic. I encourage you to check it out.

I was happy to make a recent contribution to The Territories, a story and photo gallery about Australia’s abundance of deceptive orchids:

“Sex, Lies and Pollination”

Rather than luring its pollinator with the promise of food this flower uses an equally, if not more, powerful motivator: sex. Undetectable to human senses, the orchid’s advertisement is a precise chemical mimicry of a female wasp’s sex pheromone. This is targeted marketing at its finest, as the use of a signature sex pheromone ensures that the orchid attracts only males of a specific species of wasp.

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The Toadlet Diaries 2: Gulf country.

In 2010 I was fortunate to accompany herpetologist Dr. Renee Catullo on a trip through Australia’s Top End collecting little brown frogs. Here are some of my field notes along with photography. While my photography has vastly improved, I’m not sure I’ve felt so inspired to write since that trip. I hope this series of vignettes communicate some of the flavour and excitement of the wet season in Australia’s monsoon tropics.

(Part one here)

31 January 2010

I was relieving myself a stone’s throw from the inundated Carpentaria Highway when I saw my first Brolga. Its lanky form drifted indolently against a pastel sky as the tropical sun poured out late afternoon’s final slanting blaze. I finished my business, picked up my binoculars and shovel, tucked the bog roll under my arm, snatched a nearby burrowing frog with my free hand and wandered back to where Steve had left our hired Landcruiser: bogged up to the axles in the soft roadside sludge.

We had been following a map to the “Lost City”, scrawled on a take-away order pad by a gnarly-toothed cook at Cape Crawford’s “Heartbreak Hotel”. (This sentence is entirely true and gives me great pleasure to write). I had hoped to see the exceedingly elusive Carpentarian Grass-wren there, but like Grass-wrens, Lost Cities are difficult to find. Renee planned to make a 200 km push down and back the Tablelands Highway that night so our search for the Lost City was truncated in favour of beginning the evening’s driving. Our U-turn was truncated on the shoulder of the highway, which had been under floodwater for the last 3 or 4 days and needed little persuasion to engulf the hired Landcruiser.

We had been stalking 300 kms of the Carpentaria Hwy for the last two nights and had seen one car in that time. It was 5.30pm on Sunday and we had enough food and water in the car to last us a few nights should it come to that, but in a great fluke of variance the next 30 minutes sent us three different cars. Our eventual saviour rocked up in a big old Landcruiser. As a spry indigenous woman jumped out of the passenger seat to retrieve a rope from the tray, a man as weathered, wide and red as our fair country hopped out of the driver’s seat. Our saviour was in a hurry, the rope quickly linked our cars back to back and he barked some instructions to an unsure Steve behind the wheel of our stricken vehicle. Soon wheels were spinning as his truck revved and squealed, switching about like a hooked barramundi. Steve eventually found 4WD, low range, reverse and our steed was yanked backwards from the muck.

Impeded on the Carpentaria Hwy

Impeded on the Carpentaria Hwy

That was the beginning of one of the most eventful evenings of the trip. We were now running a bit late, but counted ourselves lucky to have gotten away with an hour delay. The drive ahead saw us traveling south down the Tablelands Highway, a road that splits rocky cliffs of rust red upon which the ivory white bark of eucalypts is thrown into dramatic contrast by the light from the setting sun. We stopped on a vast flat grass plain after dark and watched the moon rise, a giant languid yellow disc that was to light the rest of our evening.

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It is worth mentioning that I only refer to the roads by name because there are so damn few of them here in the Top End. Each road takes on a character through its interaction with the elements, the lansdscape, and the idiosyncrasies of the disparate roadhouses, towns and remote communities it links across vast distance. These bitumen ribbons of country and the hours spent on them forms a large part of the Top End experience for residents and visitors alike.

Soon after dark the animals started throwing themselves in front of the car. A remote wet season highway at night is chaos. I’ve never seen so much wildlife ever, and you’ll be pleased to know most of it survived. Bustards, nightjars, owls and curlews appear in the headlights, I brake and they make a flapping flash in my periphery as they fly within centimetres of the windscreen. Agile wallabies bound in groups across the road ahead, or sometimes they just stand on the road shoulder, waiting for us to drive closer before darting out into our path. The road is littered with frogs, only discernable as the car drives on over them. But one can’t look out for them as it is much more important to spot the groups of Brahman cattle from a distance safe enough to slow down. At several points we’re slowed to sub 10 km/h as dozens of cows slowly bumble down the road in front of you for hundreds of meters. There is nothing to do but travel along behind until they find a spot to vacate the bitumen. In addition to the fauna there’s water to watch for, the road is flooded in some points up close to a meter, and the floods have dragged onto the road a flotsam of logs, branches and general crap to drive around.

Tablelands Hwy denizen with biologist for scale - Black-headed python

Tablelands Hwy denizen with biologist for scale – Black-headed python

When we swapped drivers I had run over what I was horrified to hear Renee later estimate as a total of 30 burrowing frogs. At the wheel, Steve the frog lover perhaps avoided a few more than I did, but unfortunately he was unable to avoid a nail tail wallaby. The nail tails are beautiful creatures up close, covered in soft, fine light caramel fur with faint white markings. A dark dorsal line runs from the back of their neck down their spine to the nail protruding from a spray of thick black bristles at the end of the tail.

That was one day in gulf country, out near Boroloola.

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The Toadlet Diaries 1: Trench warfare frogging.

In 2010 I was fortunate to accompany herpetologist Dr. Renee Catullo on a trip through Australia’s Top End collecting little brown frogs. Here are some of my field notes along with photography. While my photography has vastly improved, I’m not sure I’ve felt so inspired to write since that trip. I hope this series of vignettes communicate some of the flavour and excitement of the wet season in Australia’s monsoon tropics.

3 February 2010

Birds, wind, insects, all still, all silent. An atmosphere of exhaustion settles in as the temperature draws near 40. Wanda Inn roadhouse sits baking between red clay and the azure expanse of the outback sky. This would be home for the night, and we’d best get some sleep before tonight’s activities.

Littoria caerulea find respite from day's dry heat by hanging out in the toilets.

Littoria caerulea find respite from day’s dry heat by hanging out in the toilets.

The area hadn’t seen rain for a while but on dusk the moodily flashing cumulus clouds in the distance promised a change in the weather. Soon after dark we find ourselves in frogless country, standing on the roof of the Landcruiser captivated by the lightshow of distant electrical storms. As time passes the breeze blows harder, and we drive closer to its origin. Soon we are buffeted by a stiff cool wind, petrichor fills the air, fat drops of rain spatter and we are surrounded on all sides by the intermittent discharge of three kinds of lighting. Coruscating bolts crack somewhere between us and the horizon, leaving their jagged after-image in negative on our retinas, snaking fingers of electrical tracery race bifurcating and branching in the clouds overhead, and distant bolts diffused through cloud and rain suddenly bathe the land in white, turning puddles into mirrors for the silver sky before plunging us back into darkness. The weather is completely in character for the Northern Territory: at once utterly romantic and dangerously thrilling.

We stop periodically to stand on the car and take pictures of the gathering storm (still no frogs calling) but when a blinding bolt cracks too close for comfort we quickly curtail our roof-standing. Discouraged by the lack of frogs, the talk turns to gin and tonic at our next stop, but when we get there, rather than a refreshing drink, the distinctive chip of the Stonemason toadlet greets us and the frogging is on.

And so the wind blows, fat drops spatter our skin as we stride through waist high grass and negotiate ankle-twisting holes, boot-sucking puddles, and mud that cakes to the mud that’s caked on the mud caked on our boots. We wiggle between the slick ground and barbed wire fences while the sky flashes chaotically, rumbling and booming, and we stalk around pools thronging with the disorientating din of burrowing frogs, occasionally glimpsing the wide eyes of the other when the land in an instant becomes awash in the white of a nearby burst of lighting. This was trench-warfare frogging.

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Sex, Lies and Nectar: Evolutionary Biology as Written by Flowers

I spoke to the Canberra Skeptics group earlier this week, on a subject most near to my heart. The abstract appears below. It is my aim to soon turn elements of this into a video for online audiences.

In the eyes of evolution, finding a suitable mate for reproduction is one of the most critical stages in any organism’s life. The great majority of flowering plants have outsourced this essential service to animals, giving rise to a fascinating evolutionary dance between plants and pollinators.

Charles Darwin was the first to recognize that flowers were superb teachers of evolution. I will touch on his classic work and explain what we have since learned about remarkable flowers who smell like dung and death, flowers who attract insects with the false promise of sex and a fly with a ridiculously long tongue.

These and other awesome examples of floral evolution would surely have thrilled Darwin, and may even solve his “abominable mystery”: the rapid rise of the spectacular diversity of flowering plants.

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Male thynnid wasp gripping tightly to the lure of the hammer orchid (Drakaea glyptodon).

The Genetics of White and Gold, Blue and Black: A Holler to 23andMe

The internet is currently losing its collective composure over the perception of colour in the following unremarkable photograph:

Blue and black, or white and gold?

Buzzfeed’s explanation invokes the illusion of compensation; that a single shade can be perceived in multiple ways depending on the lighting context (see image below). There is an excellent write up of the illusion on Jerry Coyne’s blog so I won’t go into any more detail on it here. But you should click through to see a vivid example of the illusion in action.

Compensation illusion: A and B are the same shade.

What I am more interested in is the ratio of “Black and Blue”, to “White and Gold” in that Buzzfeed survey. The sample size is large (>200000 people have voted), and those numbers look suspiciously Mendelian, which got me thinking that perhaps there might be an opportunity to look for a genetic link to colour perception.

Source: Buzzfeed

For those who remember high school genetics, Mendel was the Monk who discovered genetic inheritance by crossing pea flowers of varying colours. When we refer to simple inheritance of traits they are often described as “Mendelian”. At a single locus, perhaps there is a dominant ‘White and Gold’ gene, and a recessive ‘Blue and Black’ gene. At equal frequency in the population, one would expect the phenotypes (white/gold versus blue/black) exactly as shown in the survey. That’s a lot of “ifs”, and highly unlikely, but it is possible that there may be some genetic control underlying this variation in perception.

Mendelian inheritance

Is it possible that compensating in colour perception could be partly influenced by just one locus? It sounds absurd, but if this is not some elaborate trolling then it might actually be a real possibility.

This is where you come in 23andme! As holder of one of the greatest collections of human genetic variation data, I implore you to carry out the white and gold, blue and black survey yourselves. Linked to 600,000 single nucleotide polymorphisms for over 1 million people, we could get a pretty powerful association study done really quickly. The result could tell us something fascinating about the genetics of perception.

Pollination, evolution and an orchid’s seductive ruse.

In a PR coup for dumpy little green orchids everywhere, research from my PhD recently landed on the cover of the journal Evolution. But what is it about?

Spring. The Blue Mountains, west of Sydney. Altitude 1000m. Frosty winds whip a swaying eucalypt canopy infiltrated by billowing cloud. Down below, amongst snowgrass tufts, rotting logs and bracken dwell the diminutive bird orchids. Genus: Chiloglottis. They huddle in tight colonies, sporadically sprayed by the high country squall.

Each plant holds two leaves pressed flat to the damp ground. Between the leaves a stem rises, holding aloft a single intricate flower in dusky shades of green and burgundy. When banks of cloud give way to azure sky and the shrike-thrushes resume their piping, these small blooms become irresistible lures.

Their target are the gracile flower wasps. Slim glossy black insects, zooming silently on shimmering wings. They are helplessly drawn to the flower. The bird orchid is emitting a scent, detectable only to wasps, which signals the promise of a mate. Known as ‘sexual deception’, the elaborate ruse uses a precise mimicry of female wasp pheromones to fool male wasps into pollinating the orchid.

However, here on the forest floor there is not only one species of orchid outwitting wasps for its own reproductive ends. Look closer and slight differences in the characteristics of flowers and visiting wasps betray something more complex and interesting. There are actually two species here, looking largely the same, growing in the same places, both deceiving their wasp pollinators through the false promise of sex.

By emitting subtle variations of their chemical trickery, these orchids have “tuned in” to two different pollinator species. This research paper explores this phenomenon as a way of separating the gene pools of closely related organisms. At the heart of it, the story here is about the forces that keep species apart once they split, or reproductive isolation.

First, we show that the different pheromones emitted by the two orchids are responsible for attracting different pollinators. Through arcane powers of chemical synthesis that I do not understand, chemists created synthetic orchid pheromones for us. We took these into the landscape and showed that the two chemicals attract two different wasps. The only perceivable difference between the wasps involved is yellow spangles on the carapace of one of the varieties. What’s more, this specific attraction is exclusive. Chemical A only attracts wasp A, and chemical B only appeals to wasp B.

Next, we take real flowers of both kinds and place them in a row and watch the hapless wasps roll in. We see that wasp A is only attracted to flower A, even when flower B is present just centimetres away. The results are identical to the results of the synthetic pheromone experiment.

On the basis of scent, we therefore expect that orchid A may never mate with orchid B. Exclusive attraction ensures that despite living amongst one another, some orchids may never exchange genes. Despite looking almost the same to us, they may as well exist on separate islands. They distinct separate species.

In order to back this up we then looked at the genetics of the species. By using the same kind of genes used in human DNA fingerprinting we were able to show that the two kinds of orchid exhibit differences in their gene pools of a degree expected if they were different species. Furthermore, analysis showed not a single individual displaying the genetics of a hybrid. Our last tests were to make hand-pollinated hybrids to check that hybrids could indeed form. These crosses showed hybrid offspring germinated and grew faster than pure crosses.

The potential for animals to drive the formation of plant species has long been recognized. This study gives us a strong case study of how that process might look. Our orchids are spectacular examples of the power of pollinators to create and maintain plant species. Through selective pollinator attraction, the orchids have been set upon unique and separate evolutionary journeys.

Further reading:

Whitehead, M. R. and Peakall, R. (2014) Pollinator specificity drives strong prepollination reproductive isolation in sympatric sexually deceptive orchids. Evolution 68: 1561–1575. doi: 10.1111/evo.12382

Rod Peakall and Michael R. Whitehead (2014) Floral odour chemistry defines species boundaries and underpins strong reproductive isolation in sexually deceptive orchids Annals of Botany 113 (2): 341-355 first published online September 19, 2013 doi:10.1093/aob/mct199

Plant pollinator interactions in the South African flora

The slides from my recent departmental seminar at the ANU are below.

The first half of the talk concentrates on plant-pollinator interactions, floral guilds and floral evolution. The second half is a slideshow of vistas, creatures and plants I encountered in my work.