GENERAL VEGETATION OF THE LITTLE KAROO
· Bossies - long lived, deep roots, small leaves, often spiny
· Annuals - very short lived, small soft herbs, large attractive flowers, excellent seed dispersal
· Geophytes - bulbs, underground storage of food and some water, can flower without leaves (flowers are vulnerable to water loss)
· Succulents - fleshy plants storing mostly water
SUCCULENTS (Succulence is a way of life, not a botanical classification) About 30 different plant families have evolved some succulent species. Water may be stored in leaves or stems. The sap may be watery, milky, salty etc. If it is poisonous it reduces the danger of being browsed. The dissolved substances make it act as "anti-freeze" so the cells don't burst during frosty conditions. DESIGN A SUCCULENT Your plant should lose as little water as possible but still be able to perform these essential functions · Photosynthesis - needs Carbon dioxide, sunlight, water, chlorophyll · Respiration - needs oxygen, releases energy · Growth - making more cells, making those cells bigger and stronger (woody) · Water uptake and transport - this usually involves pulling a 'column' of water right through the plant. Remember that water loss occurs at flat surfaces, but so does photosynthesis. A sphere has the lowest possible surface to volume ratio. Loss of water from the leaves pulls more water up through the roots. Leaves have stomata (pores) to take in carbon dioxide and oxygen, but water is lost through the same route. Sunlight is necessary for photosynthesis, but it heats up the plant sap and speeds evaporation. Think "trade off".

SOME COMMON FLOWER FAMILIES WHICH HAVE DEVELOPED SUCCULENCE

ASTERACEAE Daisies are often herbaceous annuals, but a big group have become long lived succulents. They have typical daisy seed dispersal which is very efficient. (A complex flowerhead with many tiny, single seeded flowers, enclosed in an involucre of bracts)

CRASSULACEAE Leaf (Cotyledon) and stem (Tylecodon) succulents. They have a primitive flower with the carpels of the ovary not joined together.

ASPHODELACEAE (Liliaceae) The main monocot family among succulents. Aloes, Haworthias, Gasterias etc mostly leaf succulents.

AIZOACEAE This includes all the Mesembs which are so numerous that they were given their own family for a while. The flowers are brilliant, with many stamens; what look like zillions of petals are actually coloured outgrowths from the stamens. Fruits are complex quintagonal capsules. Leaves are succulent and opposite; the whole plant can be reduced to only 2 leaves.

EUPHORBIACEAE Typically stem succulents with milky sap. Flowers interesting but not usually brightly coloured.

ASCLEPIADACEAE Includes the carrion flowers like Stapelia and Orbea.

PORTULACACEAE Portulacaria afra (spekboom) and "gansmis"

When the desert blooms, the evolutionary history of the plants shows up. The plant bodies can be incredibly similar, but the flowers indicate their ancestry. It seems that only flowering plants (Angiosperms) have become succulent. Mosses and ferns grow in the Little Karoo, but they seem to cope by drying out and going into a state of suspended animation.

ANNUALS (very often daisies) These grow very quickly and spend the unfavourable season as seeds. Very efficient seed distribution - parachutes, wings etc. Seeds aim for places which are good (like where the parent plant was the previous year) others are scattered far to exploit any place where it is possible to grow. Some flowers like Dimorphotheca produce 2 kinds of seeds - heavy ones which drop straight down and corkscrew into the ground, and light windblown ones.
Germination - all sorts of strategies exist: inhibitors to delay germination, intensity of the trigger needed (rain and light are usual cues, cf fire in Fynbos) Seed investment - few large vs many small. Good chances for genetic variability with regular cross pollination and short life spans.

BOSSIES These are long lived plants, so they don't need to have efficient reproduction every year. Good growing spots are already being used, so it is more difficult for germinating seeds to find a niche. They have deeper roots which reach to ground water and can often survive longer droughts than the shallow rooted succulents. Because they don't have to start afresh so often, there is less speciation.

GEOPHYTES Bulbous plants reproduce vegetatively in good spots, ie the mother plant which has grown well there makes offspring bulbs or corms. - no genetic variation. They also flower strongly, often with specialised pollinators, form seeds which enable them to colonise new areas and this promotes genetic variation.

SUCCULENTS Vegetative reproduction is common - broken off leaves (with a tiny piece of stem) grow roots and become new plants. Genetically, this means no variation: "If it isn't broken don't fix it". Make the most of habitats which have already proved good. Flowering and seed formation occurs most seasons. (Some Crassulas flower only once in their lives, investing all their resources in this) This leads to the possibility of genetic variation. Germination strategies prevent all seedlings being lost in the same event. Distribution of seeds from the capsules depends on the presence of water. Special tissues expand when wet and open the capsule. Succulents have lifespans shorter than the "bossies" because very extreme droughts kill them off first. Regular destruction of populations by extreme environmental events, combined with a gene pool limited by insect flight and water dispersal of seeds seems to have led to the extreme speciation in the Mesembs.

POLLINATION Any wind pollinated species? Flowering is in the damp season when it is too cool for insect activity? Spring is a compromise here - still wet enough, getting warm enough. In massed displays there is fierce competition for pollinators. This has led to more and more eye-catching flowers. Some have specialised pollinators, giving specific rewards.

CONCLUSION The Klein Karoo plants are well adapted to their environment, using many different strategies.

There is huge biodiversity - mostly at the species level. This speciation may have resulted from small plants with a limited range of pollinators, and seed dispersal, having mechanisms to ensure cross-pollination and with a relatively short lifespan.

Subtle variations in soil composition, soil moisture, shade, etc result in niche environments. The overall result is a mosaic of communities, often with local endemics.