Tuesday, March 13, 2007

A simple comparison between a Madagascan and a typical Cape Flats species (within the context of the Gondwanan split)

The Restionaceae family enjoys wide distribution in South Africa and is more restricted on the larger African continent. The current distribution appears to have underlying gondwanan origins (Linder et al, 2003). Linder et al (2003) further suggests that west Gondwana (Africa, South America) separated from east Gondwana (Australia, Antarctica, Madagascar, India) approximately 180-150 million years ago in the Jurassic. Therefore the restio species of Madagascar have been (to a large extent) evolving separately from those extant on the African mainland for more than 150 million years. Below are some differences between a South African Cape floristic species (Thamnocortus spicigerus) and one of only two species found on the island of Madagascar (Restio mahonii ssp. mahonii). The sketching of these differences aim to show that they have evolved considerably different mechanisms for survival in different habitats.

Restio mahonii ssp. mahonii

Altitude: 1500-3000m
Habitat: marshy and found in shallow soils over rock
Bedrock: granite
Root structure: stolons
Smoke effect on seed germination: unknown

Thamnochortus spicigerus

Altitude: 0-50m
Habitat: Well-drained, deep coastal sands
Bedrock: alkaline coastal sands
Root structure: rhizome
Smoke effect on seed germination: significantly increases germination


For this mini-assignment, I narrowed in on two genera of Restios, namely Mastersiella and Rhodocoma, each represented by a single species on the Cape peninsula (Cape Point area). I was most interested to discover that of the 350 known taxa that make up the Restios, 107 of them are found on the Cape peninsula, that's just over 30% of all taxa! Only the genera Mastersiella and Rhodocoma out of all the other genera that are encountered sympatrically, are represented by a single species. I wondered why...

This is Mastersiella digitata:

Mastersiella digitata is typically 0.2 - 0.7m tall and does not have spreading rhizomes, therefore it is also vulnerable to fire and will not resprout after a fire event. The distinguishing characteristic of this species from the other species within the genus is shape of the cone-like spikelet of the male flower, which are also reflexed. This species is distributed along coastal mountains from 20m - 50m above sea-level, so it is generally a low-altitude species. Its seeds are dispersed by ants who make use of the elaiosome through a mutually beneficial relationship which sees the role of the ant as the "seed planter."

Mastersiella purpurea (named after its purple colour) has a different growth form to M. digitata. M. purpurea is typically erect, while M. digitata is short and tufted. Mastersiella purpurea is also taller and grows to 0.5m - 1.5m tall. Mastersiella purpurea seed dispersal strategy is the same as M. digitata, as is its vulnerability to fire, but M. purpurea is found at a higher altitude range of 300 - 1600m above sea-level. Mastersiella purpurea is not found on the Cape peninsula.

Mastersiella spathulata (named after its shape, similar to that of a spoon) is similar in height to M. digitata at 0.2m - 0.6m tall, and is also tufted, not erect. It is found commonly on acid coastal sand as far East as Bredasdorp. It also has a wide altitude range of 50m - 1900m above sea-level. This species however is also not found on the Cape Peninsula.


Interestingly, there are a few factors which seem to be important in the distribution of these three species above. The reason why M. digitata is found solely on the Cape Peninsula is linked to the soil-type and winter rainfall. Low altitudes also suggest that M. digitata is more resistant to salt spray from the waves which pound both sides of the Cape Peninsula, and their shorter growth form is probably more efficient in this wind-swept region, which could probably cause damage to taller forms. Mastersiella purpurae is found mostly in the Southern Cape where the area receives Summer rainfall, and at the altitude above 300m, it is placed away from salt spray of the sea and possibly within the mist-belt of the Cape folded mountains which would also provide a higher intensity of year-round precipitation. The taller growth form possibly suggests that wind is not an important factor. Mastersiella spathulata is the most common of the three species and can adapt to a variety of areas. It also prefers slightly wetter climates, but has adapted to drier environments. This species prefers acid coastal sands, which is probably why it is not found on the Cape Peninsula, since its altitude range suggests that it could possibly live here.

A common and very interesting factor between all three species is that the seed dispersal agents (ants) must be extremely diverse and capable of making use of a variety of climatic conditions and environments from low coastal altitudes to alpine heights at the tops of mountains. Ants are extremely successful.

This is Rhodocoma fruticosa:

Rhodocoma fruticosa is 0.4m - 0.8m tall, and grows almost exclusively on cave sandstone substrate. It gows at altitudes of 200m - 1600m above sea-level and is the most widespread of all the Restios in South Africa. It has adapted to live in both Winter rainfall regions as well as Summer rainfall regions. In Winter rainfall regions it is commonly associated with dry Fynbos at the lower altitudes. Rhizomes are present and it can therefore regenrate after a fire event. The seeds of R. fruticosa are "seed surface type" and are not dispersed by ants. The seeds therefore do not possess elaiosomes.

I believe that the only reason why R. fruticosa is the sole representative of the genus from the Cape Peninsula, is because it is the most likely of all the species within the genus to survive there. This must suggest that the Cape Peninsula is either a very specific habitat, or a very harsh environment that restricts the successful recruitment of other species within the genus. Rhodocoma fruticosa is the most common species in the genus and therefore must have adapted to a wide variety of different climates, possibly predisposing it to the conditions on the Cape Peninsula as a survival advantage or adaptation over its related species. Its seed dispersal agent must also be present on the Cape Peninsula.

For both genera, although much work is missing regarding the role of fire in germination of seeds, it seems as though Restios with rhizomes, which are adapted to resprouting after a fire-event, produce either wind-dispersed or larger-animal dispersed seeds (birds?), while those which are killed off by fire because they cannot regenerate, produce hard, woody seeds which are taken underground by a large variety of different ant species whose home is the Fynbos area. In times of fire, the ants would be protected underground as would the seeds of the Restios which they took down with them, and maybe the behaviour of the ant species after a fire, such as nest relocation, or other response to the fire-event, could play an important link in the success and germination of the seeds to support the next generation of these Restios.

All of this from a key...


David Vaughan
Senior aquarist, Quarantine
Two Oceans Aquarium
Cape Town, South Africa
+27 21 418 38 23

Image credits:

Mastersiella digitata: Image from Fernkloof Nature Reserve: (accessed 12:47; 13 March 2007).

Rhodocoma fruticosa: (accessed 13:47, 13 March 2007.)


Restionaceae are one of the three commonly referred to elements of the Cape Floral Kingdom. They are all perrenial, evergreen and have a grass-like form and all have reduced leaves (only sheaths) and the stems are the site for photosynthesis. Sexes are on separate plants (dioecious), and their flowers are usually small and wind pollinated. The seed of restios are small seeds, nut(winged or non-winged)and a significant number possess an elaiosome for dispersal by ants. The Family Restionaceae is represented most dominantly in South Africa (350 species, subspecies and varieties) and Australia (ca. 150 species). New Zealand has four species and South America has one species. There is only one representative north of the equator and is wide spread in South East Asia. Restios are becoming increasingly popular world-wide in the horticultural industry since they are tough, virtually maintenance free and have slightly unsual decorative value (visit Willowbridge Shopping Malls/Tyger Valley Waterfront) to see en-mass landscaping).

Restionaceae Origins

The Cape Floristic Region is the real heartland of the Restio family, where they dominant much of the landscape. Their origins appear to date back to the Cretaceous (60 million years ago)- so they were around well before grasses and sedges made their appearance. Possibly there were the only grass-like angiosperms that lived when the last dinosaurs were around – but they would not have attempted to eat them. There are few plants, if any as inedible as restios (that’s why horticulturalists like them), and really only specialized insects can make a living on restio salad. The Restio Leafhopper (Cepalelus) is one highly adapted insect that is present in large numbers on the Restios in the Dog-Leg section of the UWC Campus where the University Admin propose to build the new Life Sciences Centre (see my posting). It is generally accepted that restio have an ancient Gondwana origin and is based on some fossil pollen records. This would explain their presence from South America to New Zealand when the land masses had not broken up and the group had already radiated into each of the future regions of the southern hemisphere. An alternative hypothesis for their distribution across all southern land masses is that the family crossed the Pacific Ocean only relatively recently (30 million years ago) leading to the establishment of the sole South American representative which is closely related to a species from New Zealand.

Restionaceae in Africa

In Africa there are some 350 taxa, but they are overwhelmingly concentrated in the Western Cape (341 taxa) with Eastern Cape and Northern Cape having 47 and 35 taxa each. The Northern Province and Kwazulu Natal have 10 and 6 taxa respectively. There is one taxa each in Lesotho, Mapumalanga and Zimbabwe and two taxa in Malawi and Madagascar.

Restionaceae: Habitat preference

The majority of Restios occur on Table Mountain Sandstone (302 taxa), with a further 42 taxa found on the acid coastal sands. A further 23 and 21 taxa are found on the more nutrient –rich granites and shales respectively. Limestones and alkaline sands have only 15 and 8 representatives. Consequently restios generally most speciose on nutrient poor and acidic conditions such as occurs in our Mountain Fynbos vegetation.

Restionaceae: Fire adaptations

Since fire is an important form of disturbance in Fynbos communities, restio are fire adapted with virtually equal representation (122 and 123 taxa) in coppice regeneration and by seed (where the parent plants are killed). There is only one species that appears not to be fire-adapted Thamnochortus spicigerus which the parent plants are killed by fire and there is poor regeneration from seed. There appears to be little information on germination cues but some eight taxa postively responded to the influence of fire smoke.

Restionaceae: Seed dispersal

Some Restionaceae have relatively simple seeds contained in capsules which splits to release them. The seed size is typically 1-2 mm. In other species a single seed is formed to produce a nut with a variaety of dispersal methods ranging from winged seeds to possessing an elaiosome for dispersal by ants. Even the colour of the elaiosome is white, green or olivaceous. In some species the nut can become quite large (>11 mm) as can the elaiosome (10 mm).

Restionaceae: Growth forms

In growth form most restios are tufted, but sprawling and grass –like forms also exists Less than a third (100 taxa) of Restios appear to have a rhizome and some 77 have a stolon. About 211 restios are without rhizomes or stolons. Restios generally range in size from about 100 mm to the largest forms that are almost 3 m in height.

Restionaceae: Economic value

In terms of economic value, their most important use would be for the thatching industry where nine species are commonly used (Cannomois, Thamnochortus and Willdenowia). Thamnochortus insignis is especially abundant and used in the Bredasdorp area. At least 39 taxa are used in the horticulture industry from the UK to California with Cannomois, Elegia, Ischyrolepis, Restio and Thamnochortus being the most popular. Virtually no restio have economic value for grazing. Although there are no records of restios becoming invasive outside of their home country (I checked using Google Search and various Invasive Alien Species checklists), Thamnochortus insignis populations have established all around Hermanus and where it was introduced as thatch material for roof construction.

Restionaceae Conservation

Since Mountain Fynbos is relatively well conserved most members (256 taxa) are not threatened. Only one species of restio is know to have become extinct Willdenowia affinis) with only eight taxa endangered, 21 vulnerable and 53 considered to be rare.


Additional Notes

I have illustrated what can be extracted within 15 minutes of use of Peter Linders’s The African Restionaceae Delta Database vs 2. July 2002. It took about 60 minutes to write this posting. In class you were provided with more than this time. You can either post your own description of the Restionaceae or post comments on this article indicating gaps and other useful information. The intention was to make you think about what features are useful in developing a taxonomic key – it was NOT meant as another exercise. Please remember the external’s evaluation of your work is based mostly on how you have contributed to our Course Blog.