Ecological Islands within the Continent of Africa (Part-1, the Cape of Good Hope)

I scour the latest scientific journals, looking for material I can write about on my blog.  The focus of my blog is meant to be on the paleoecology of southeastern North America during the late Pleistocene.  My writing output, however, is more prolific than the number of new studies being published.  I wish there was an army of scientists researching ancient evidence of plants and animals in the region, but instead there are probably less than a platoon’s worth.  So I’m forced to delve outside the region for blog fodder.

Recently, while researching something else, I discovered a wonderful book published in 1989 by Jonathan Kingdon entitled Island Africa: The Evolution of Africa’s Rare Animals and Plants.  The premise of the book is that climate and geography have worked together in Africa to isolate many different natural communities into ecologically diverse islands.  For example climate change has caused deserts and savannahs to expand, thus isolating regions with tropical forest that were once connected.  Closely related organisms of the forest then evolved into different species because of this isolation.  Conversely, tropical forests grow between deserts and savannahs and isolate organisms that prefer dry open environments, resulting in speciation of grassland organisms.

While reading this book, I learned about many species of plants and animals that I did not know about.  Because I’ve so thoroughly studied and speculated about the flora and fauna of Pleistocene North America, I thought it would be a refreshing change to cover Africa’s paleoecology for awhile.  Pleistocene North America was a great untouched wilderness until man colonized the continent about 15,000 years ago, and it’s fauna has often been compared to Africa’s.  This is a misguided perception because Africa’s wildlife is much more diverse than that of North America during the Pleistocene.  (See: https://markgelbart.wordpress.com/2013/12/09/the-faunal-diversity-of-pleistocene-north-america-was-less-than-that-of-modern-day-africa/ )  South Africa, the first “ecological island” I’m writing about has 30 species of antelope alone.

Several physical barriers isolate South Africa from the rest of the continent.  Cold mountains block the exchange of tropical species.  Deserts are an insurmountable obstacle for forest species.  And wide rivers are an impediment for animals that avoid swimming.  The Cape of Good Hope includes a wide range of environments including desert, savannah, montane grassland, evergreen heath, woodland, and coastal forest.  Antarctic and tropical currents offshore create an unusual climate consisting of dry summers with frequent fires and cool moist winters that mostly stay frost free (though snow and frost do occur in the mountains) so that plants can grow well then.

Many interesting plants that are fire tolerant and can take advantage of winter precipitation grow in this region  Over 20 species of cycads, a primitive gymnosperm, grow here.  Sugar bushes are also endemic.

 

 

 

 

 

 

 

 

 

 

Cycads are common in South Africa.  They are primitive gymnosperms that first evolved 250 million years ago.

Sugarbush (Protea) blossoms, Harold Porter National Botanical Garden, Betty's Bay, South Africa, Africa Stock Photo

Many species of sugarbush are native to South Africa.

Flowering plants such as geraniums and gladiolus originated in South Africa, but ironically are now rare in their original environments though they are commonly cultivated in flower gardens around the world.

Pelargonium cucullatum Contour Path Rhodes Mem.JPG

Wild geranium in its native habitat.

South Africa is home to several species of primitive antelopes that formerly were widespread throughout the African continent during the Pleistocene.  Other more advanced species of antelope outcompeted them on most of the rest of the continent, but for various reasons grysbok (Raphizera melanotis), rhebok (Pelea capreolus), bluebuck (Hyppotragus leucophaeus), and white-tailed gnu (Connochaetes gnou) held their ground in South Africa until European settlers overhunted the latter 2 species.  Bluebuck became extinct in 1798.  Conservationists saved white-tailed gnus, and this species is making a comeback.

White-tailed gnu; Marwell; 18th July 2010

White-tailed gnu are native to South Africa.

Rhebok with a broken right horn.

European settlers also overhunted the quagga (Equus quagga quagga) into extinction.  Zebras that live farther away from the equator have fewer stripes.  A species of zebra lived in North America until the early Pleistocene.  It likely resembled the quagga.

Quagga_photo

The only specimen of the quagga ever photographed.  It is now extinct.

The golden  mole (Neamblysomos julianac) is also a primitive species unique to South Africa.

Neamblysomus julianae (Meester, 1972)

The golden mole is endemic to South Africa.

The ground-nesting woodpecker (Geocolaptes olivaceoc) nests in underground burrows dug into sandbanks. This is very unusual behavior for a woodpecker.  It’s also one of the largest species of woodpeckers in the world.

The ground-nesting woodpecker is endemic to South Africa’s montane grasslands.

Reference:

Kingdon, Jonathan

Island Africa: The Evolution of Africa’s Rare Animals and Plants

Princeton University Press 1989

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