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.

Roses reflect greatest above 620 nm, Violets reflect at 420 – 480 nm…

Roses are red,  Violets are blue,  Botany is sexy, But less so than you.

Roses are red,
Violets are blue,
Botany is sexy,
But less so than you.

Along with odour, flower colour is perhaps the most important cue plants use to advertise to pollinators. Change the colour of a flower and that change can have large consequences on which pollinating animals are likely to visit[1]. Bees, for example, are attracted to purple flowers with UV highlights. If that plant were to mutate to white, it could very well find itself being visited by nocturnal moths[2].

In studying plant-pollinator evolution and ecology, it is very important then that we have some objective quantification of the colour of a flower. Human eyes are famously fallible and many insects and birds can see outside the range of our colour vision (400 – 700 nm).

The instrument we use is a spectrometer[3]. It uses optic fibres to bounce an initially white-light beam off the surface you want to measure. The wavelengths of light that are reflected (as opposed to absorbed) determine the colour of the surface you are looking at. The spectrometer collects the reflected light, separates the wavelengths through diffraction and digitises the signal. The result is a graph such as the one above.

In the graph, the wavelength is given on the horizontal axis, while the proportion of reflectance is on the vertical. The rainbow bar above provides an approximation of how the human eye perceives a given wavelength of light. The rose therefore will reflect greatest at wavelengths above 620 nm, the red part of the spectrum. A violet most strongly reflects around 420 – 480 nm. A pure white surface would show high reflectance across the range of the visible light spectrum.

Dedicated to my sweetheart, who for the second year in a row has been alone on Valentine’s.

Kniphofia are red, Agapanthus are blue.

Fieldwork is fun, But I do miss you. 

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.