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.

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

Mount Gilboa’s meadows.

This has been my sometimes workplace for the last two weeks:

The slopes of Mt. Gilboa. Watsonia densiflora in the foreground.

The slopes of Mt. Gilboa. Watsonia densiflora in the foreground.

To catch pollinators in action you need fine weather. On those days when the skies are clear and there’s little more than a gentle breeze in the air, Mt Gilboa is an exciting place to be. Gleaming green Malachite sunbirds chase one another between aloes, eagles and vultures wheel overhead, a startled bush buck bounds down the slope and out of view.

On these days the flowering veld is humming with the noise and motion of uncountable beetles, bees, flies and wasps, flitting, buzzing, mating and feeding. Protea heads crawl with furry monkey beetles, massive grasshoppers zoom by on the wing and bees of varied colour, shape and size forage diligently.

The flowering veld

The flowering veld

I come here to collect long tongue flies. As you prowl among the Watsonia inflorescences you first hear the telltale loud buzz, then look for the hovering fly probing a flower with its long proboscis.

Philoliche aethiopica foraging on Watsonia densiflora

Philoliche aethiopica is a specialist forager on Watsonia densiflora. This fly’s thorax is completely covered in pollen.

Netting the flies is not too difficult—they are lazy fliers. Keeping them alive in my flight-cage back closer to sea level has proved to be the big challenge. With the season wrapping up for this site, I’m unfortunately looking at the possibility of coming away with little more than just jars of dead flies.

Watsonia lepida, common veld iris and long tongue fly host plant.

Watsonia lepida, common veld iris and long tongue fly host plant.

Despite the setback there are other research avenues to pursue as the Summer field season unfolds. The luxury of a long field season is one factor that makes this veld such a productive place to study pollination.

Test post: Captive fly video

Currently in South Africa, my time right now is largely being spent on catching flies, planning to catch more flies and working out how to keep them alive and happy in captivity. The poor little video below is a quick capture of what I wish all my captive flies would do—buzz around and visit flowers like they’re just hanging out back in the veld they came from.

More on the fly project to come in the near future.

 

I hope to use this space in future to update on research progress, life in South Africa and occasionally sound off on things of a biology, botany, entomology and overall scientific nature.

 

Thanks for looking.