Bumping into old floral friends, and pollination with a hug.

Rare plants nurseries are like second hand bookshops. It’s always so tempting to browse on the off chance you find that little treasure. I recently visited a charming rare plants nursery in Mt Macedon (boutique-y town outside Melbourne, Australia) where I discovered these for sale:

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Hello old friend! (Hesperantha coccinea)

The last time I saw this elegant iris, it was flowering on stream banks 10,000 km away in the Drakensberg Mountain range in South Africa. There in its natural habitat, it is pollinated in some areas by a very special butterfly: the Mountain Pride (Aeropetes tulbhagia). In other places, it is pollinated by the amazing long-tongue fly (Prosoeca ganglbaueri). The two forms are a wonderful example of “pollination ecotypes”, where different populations are undergoing adaptation to their unique pollinators. The fly-serviced ones are a pink hue with narrow petals, while the butterfly-pollinated ones are much redder with broader petals.

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Hesperantha coccinea at home in South Africa with its pollinator (Prosoeca ganglbaueri).

Fast forward two weeks, and I’m home walking the dog in my quite unremarkable Melbourne suburb, when who should I see?

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Hello old friend! (Diascia sp.)

It’s winter here, with very little in flower, but these brilliant little pink blooms volunteering themselves from underneath a fence in suburban Melbourne really made my day. The last time I saw a Diascia, it was growing amongst the boulders on creek beds and on cliffs in the Drakensberg Mountains. These are Diascia, or “twinspur” and its this common name that alludes to their fascinating pollination story.

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Hug-pollination by oil-collecting bee (Rediviva sp.) in Diascia.

Diascia have two spurs on the back of the flower, which is distinct from the usual arrangement of a single nectar-spur. The difference is that these flowers don’t reward pollinators with sugary secretions, instead they provide oil to specialised oil-collecting bees in the genus Rediviva. The bees use this oil to line their nests and provision their young. In order to collect the nectar, they must reach deep into the twin spurs with their lanky forelimbs, and comb it out. In so doing, they effectively hug the reproductive parts of the Diascia flower and effect pollination.

In Spring, I plan to take some cuttings from this little Diascia. Keeping species with special personal significance is a deeply satisfying part of cultivating plants. A plant can be kept like a souvenir or memento marking a time in one’s life, just like a photo or trinket. But plants have an advantage over these inanimate reminders. Because biological reproduction requires the physical donation of part of the mother’s cells to the daughter cells, my keepsake plant can be viewed as a physical part of the plant that appears in my fond memory. If I could see in four dimensions, I could literally look down the line of cell-divisions all the way back to where the Hesperantha in the nursery physically intersects as the same individual with the Hesperantha I observed flowering in the Autumn sun of the Drakensberg Mountains in South Africa.

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The Drakensberg Mountains, South Africa, Autumn 2014.

 

A most engaging mantid

Recently, I was fortunate enough to spend eight days in Ndumo Game Reserve, where for several hours a day I remained perched above clusters of large flowers smelling rather like a long-drop toilet. Tagging along as help on a study of Stapelia gigantea promised to be a chance to see a new South African biome and the wonderful creatures that come along with it.

The carrion flower (Stapelia gigantea, bottom right) in rural Zululand aloe country.

Driving to and from the field site every day we would encounter giraffe, wildebeest, nyala, impala and warthogs going about their daily activities. At dusk we’d sit in a bird hide, count waterfowl and watch crocodiles cruise on by. Our nights were serenaded by the wailing bush baby, the guttural grunting of wildebeest, the booming-bass of hippos and occasionally the manic whinny of a hyena, while the porch light drew in a bewildering buffet of invertebrate curiosity.

Croc on dusk, silently sweeping past the bird hide.

But perhaps the most endearing animal found all trip was one of the most captivating mantids I have ever seen. She is a cryptically coloured Hymenopodidae, belonging to the same subfamily as the spectacular orchid mantis. Unlike other mantids I have encountered she is very easy to handle and shows no desire to flee the hand or captivity. She is a voracious feeder and any moth or fly introduced to her enclosure scarcely lasts 5 minutes before straying too close to her raptorial forelimbs. On her second night in our field accommodation she had already laid a small ootheca.

She also displays a charming and unusual shadow boxing routine complete with weaving, jabs and feints.

Edit: I have since learned that she belongs to genus Oxypilus, a group of mantids called “Boxer mantis”, for reasons made obvious in this video. (Thanks Mantidboy for the ID).

The above video was shot with a Canon 500D, Canon 100mm f/2.8 macro in an improvised stove-top studio. A piece of white paper provided the background, the camera was stabilized on a bag of rice. This left my hands free to experiment with the lighting, provided by a cheap head torch. 

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.