JANUARY 2019
The new year is here and summer is in full swing with 186mm rain recorded at the Central area in January, so far. Everything is green and everything is growing.
I read a really interesting article in PlantLife SA (volume 46:3 December 2018) regarding the relationship between flowers and pollinators. Now, the more specific the pollinator is for the plant, the more chance the flower's pollen will reach another flower of the same species and therefore be productive. In other words, if a yellow daisy, of which there are many species, attaches it's pollen to a common Honey Bee who is attracted to all yellow flowers, the chances are not so good that the Bee will fly to another daisy of the same species without visiting many other yellow flowers on the way, minimizing the chances for that pollen to be deposited on the correct flower species. But if a flower is designed to accommodate a very limited amount of specialized pollinating insects by, for example, storing the nectar (which the insect is attracted to for food) at the end of a long spur (as is the case with many orchids), then only insects with long enough mouthparts that are able to reach the nectar will visit the flower and collect pollen on it's body to transfer to the next flower of the same design (read species).
This article involved two plant species found here at Finsbury and their associated insect pollinators. These plants form the Milkweed Family (Apocynaceae), Pachycarpus campanulatus and P. concolor are so intricately designed that only a very few pollinators can reach their nectar, the food they are seeking. These are the Spider-hunting wasps of the Pompilidae family and the Chafer beetle, Atrichelaphinis tigrina, respectively.
Pachycarpus flowers are noticeable because it is difficult to identify the flowering parts when comparing them to other flowers. The male and female whorls are fused into a structure called the gynostegium which form the central pillar of the flower. Radiating out from these are the grooved corona lobes. So the female parts are now inside the gynostegium and the male parts form pairs of flattened, hardened structures, forming the sides of gynostegium, termed "guide rails". Beneath the slit in the guide rails are stored the pollinaria, two sacks of pollen attached by a thread, resembling a minute saddle.
The nectar is produced and stored in the corona lobes which are designed to allow only suitable pollinators to reach it, and then only awkwardly! While the insect is manipulating it's body to reach this yummy nectar, one of it's legs invariable get caught in the flaired groove of one of the opposing corona lobes where it gets caught. The insect then panics and struggles to free its limb which slides up the groove of the lobe and is forced into the slit in the guide rail. The insect then pulls the leg out of the guide rail, and in doing so, the limb slides past the pollinaria and snags the joining membrane so that, when the leg is finally freed, it has the pair of pollinaria attached to it.
The insect now has to approach another flower and experience the same trauma of it's limb getting caught in the flayed groove of the corona lobes. As it enters the guide rail, the opening is too small to allow the pollinaria sacks in so, through frantic tugging, the joining membrane breaks and the pollinaria remain behind in the lobes as the limb enters the guide rails once again. From here they grow through the pillar wall and pollination is complete!
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| Fairy-bell Pachycarpus, P. campanulatus, showing the flayed corona lobes (cream colour) radiating out from the central pillar (green) with the guide rails (brown) attached to the sides. |
| A poor shot of a Spider-hunting wasp (they move too fast!) from the Pompilidae, the specific pollinator of the above Fairy-bell Pachycarpus. |
I have managed to capture many other exciting things while working in this incredible environment over the last month. Here are some of them:
I hiked to the summit of Mount Anderson quite frequently in the last month or so, and while I have always encountered special flowers up there, on my last trip I found a treasure trove of five fine orchid species! Here they are with their SANBI Red Data status:
| Disa amoena, a near endemic with four colour forms ONLY found in our area. Red Data status: Vulnerable. |
| Schizochilus cecilii ssp. transvaalensis, tiny and delicate. Red Data status: Least Concern. |
| Disa stachyoides, common but captivating. Red Data status: Least Concern. |
| The recently described, ONLY from this summit, Disa sterkeriana, mind-blowingly beautiful! Red Data status: Critically Endangered! |
| Satyrium longicauda, Common in grassland in Mpumalanga and KZN. Red Data status: Least Concern. |
February begins and the rains keep coming. Just had another heavy rainfall this afternoon that interrupted this blog. With the rains comes life! We are a water catchment reserve here at Finsbury, with exceptional fly-fishing opportunities right now. Come and enjoy it!







