Plants & Us: Fuchsia Flush - Fordiophyton brevicaule

Posted Date: Monday 15 July 2019    

There are very few populations of Fordiophyton brevicaule in the wild, probably because they require very specific environmental conditions in which to grow, with plants being found in dense forest at relatively low elevation and in close proximity to streams. Plants thrive in moist cervices and on humus over rocks, and they have slightly succulent leaves which make them modestly drought tolerant. This species can only be found in parts of Hong Kong and Guangdong, although the family Melastomataceae to which it belongs occurs throughout the tropics.

One of the prime features of F. brevicaule is its stunning fuchsia coloured petals: despite the small size of the flowers, the dazzling pink captivates an observer’s attention and the petals appear translucent when the sun shines from above. It is a miniature marvel to chance upon.

The leaves of F. brevicaule radiate a range of colours. Some display a gradient of green, whereas others exhibit a cryptic brown and copper colouration. The latter camouflage and blend in perfectly with the leaf litter in its surroundings. This protects the plants from grazing herbivores and makes them highly ornamental.

Stamen dimorphism - Division of labour of stamens

Look closely at the photo above: flowers of F. brevicaule contain stamen with two different morphologies, both of which produce pollen. These two sets of stamen differ in position, size, colour and shape. It was first proposed by Darwin that a ‘division of labour’ could solve a dilemma faced by some species of Melastomataceae between the need to satisfy pollen-seeking bees and the need to safeguard gametes from consumption. It is thought that one set of stamen provides pollen to fulfil the plant’s need to reproduce, while the other set provide foraging bees with a pollen reward. It has been shown experimentally in a related species (Melastoma malabathricum), that pollen from the purple stamen is specialised for fertilisation is significantly more likely to reach the stigma than pollen from the yellow stamen, which serves as a specialised food source. These results provide strong evidence that a division of labour is occurring between the two stamen morphologies, in order to benefit both the plant and the bees.

The key to success in division-of-labour among the two sets of stamen is not differential visual attractiveness of the stamens, but the small diameter of the anther pores through which pollen grains are ejected precisely onto particular body sections of pollinating bees. This way, the feeding stamens release their grains towards the bees’ mouthparts and thorax, while the fertilizing stamens release theirs onto parts of the bees’ bodies that come into close contact with the stigma (Luo et al., 2008).

Specifications for buzz pollination

Plants that rely on buzz pollination possess unique ‘poricidal’ anther morphology: initially completely sealed, the anther wall ruptures and releases pollen via a small pore or slit only when vibrated at a specific frequency by the wings of a pollinating bee. Poricidal anthers are thought to have coevolved in tandem with the pollinators. The adaptive behaviour of these bees allows them to extract pollen that is unavailable to other insects.

Due to habitat destruction and human interference, F. brevicaule is struggling to survive. Here at KFBG, we have succeeded at propagating the species in our nursery. We challenge you to spot them during their flowering period throughout June to July!

Reference:

Luo Z., Zhang D., and Renner S.S. (2008). Why two kinds of stamens in buzz-pollinated flowers? Experimental support for Darwin’s division-of-labour hypothesis. Functional Ecology. https://doi.org/10.1111/j.1365-2435.2008.01444.x