(Yet) another lizard story

VulcanSpirit
Richard & Alison Brunstrom
Sat 12 Mar 2011 13:19
Keen observers will notice that you have seen this lizard before, but hot off the press I can now reveal that he has been identified. He is a male Saba anole, Anolis sabanus, endemic on the tiny island of Saba. The zoology and zoogeography of these island lizards is fascinating (to some people). Most islands have only one species of anole which occupies a wide range of habitats and usually displays significant colour variation. On islands where two species coexist they occupy different habitats and the individuals are much more consistent in markings. Endemics are common - these lizards arrived by sea on these relatively young islands, and each island was presumably colonised by a small group of individuals which was therefore highly unlikely to be representative of the species as a whole. Evolution may then work comparatively quickly to form the new, endemic, species. Some Caribbean lizards are even parthenogenetic (they can reproduce asexually, males being rare or entirely absent) which is clearly a very useful attribute in a colonising lizard - only one individual needs to reach the shore in order to found a new colony. On the other hand parthenogentic species have much less genetic variability (the daughters are more or less genetically identical to their mother) being denied the genetic benefits of sexual reproduction and run an increased risk of extinction as they may be unable to adapt rapidly enough to changing environmental conditions. To considerable surprise it turns out that the largest lizard in the world, the Komodo Dragon, which also lives on a chain of small islands, can reproduce by partheongenesis. This only became clear recently when the Chester Zoo specimen laid eggs which hatched, despite Chester having no male animal. 
Watch this space for more fascinating herpetological stories by popular demand. 

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