Amazing lizard story
VulcanSpirit
Richard & Alison Brunstrom
Wed 27 Oct 2010 20:18
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As promised, more about lizards whether you like it
or not. The one below is a female Gomera lizard Galliotia caesaris,
found only here on La Gomera. It is one of a small group of similar lizards
found throughout the Canaries. Genetic studies now prove that they originated in
North Africa and have colonised the archipelago only once, spreading through the
islands from east to west and evolving into different species as they did so. As
often happens on islands some of them grew in size and four are now known
as Giant Lizards. These were not Komodo Dragons - the biggest, on Tenerife but
now sadly extinct, was only a metre long and weighed up to 2kg - but still by
far the biggest European lizard. The Giant Lizards on La Gomera and El Hierro
hang on, while the Gran Canaria species is still relatively common. The
original colonisers presumably arrived on vegetation floating on the Canaries
current (not too difficult; the closest island is only 100km off the African
coast). Iguanas populated the Caribbean island chain from South America in
this way, and recently have actually been observed colonising a new island.
Biogeography in action.
But more amazing by far is the story of
the Canary geckos.These too originated in North Africa but are now known to have
colonised the Canaries three separate times resulting in the four distinct
species found here. But that's not all. A form from the western Canaries
(genetics show) then managed to reach the Cape Verde islands 1500km to the south
where rather like Darwin's finches in the Galapagos it has evolved over a few
million years into no less than nine new species. But there is still more!
North African geckos of the same genus (i.e.very closely related) have
managed to cross the Atlantic and colonise both Cuba and the Bahamas (before
Columbus). That's a crossing of 6000km of open ocean which we ourselves will
shortly be attempting with no little trepidation in a nice big boat with
modern technology including a watermaker. I wouldn't fancy doing it clinging
onto a palm trunk and hoping for rain to drink.
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