(Yet) another lizard story
VulcanSpirit
Richard & Alison Brunstrom
Sat 12 Mar 2011 13:19
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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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