So this might sound like a dumb question, but the 'even if they are sitting next to each other' statment makes me wonder if the the snails are 'incapable' of interbreeding because of some physical or preferential impediment; and if they could still interbreed if snail A was artificially inseminated by genetic material from snail B.
The distinction might seem trivial, but here's my point: is inability to breed due to some physical mutation - say the snail ejaculates in the wrong spot, whatever- really speciation if the two organisms could reproduce with help - i.e. the sperm from snail A can still create a viable zygote when introduced to the egg of snail B?
Not a dumb question at all. The reproductive isolation in this instance is solelt 'pre-mating'. The differing chirality of the shells leads to the inability to breed, but is not actually dependent on the snail's genotype but that of its mother. Artificial insemination would certainly allow successful fertilisation, as both genotypes can be seen to be interfertile when they share the same shell chirality. Indeed the cited paper suggest that there have been reversions where a left handed population has switched back to right handedness and rejoined its parental population.
This is actually a
very bad example to give as the subsequent discussion in that thread raised the point that the paper cited does
not show speciation being observed (in the interests of frankness I suppose I should say that the discussion was between me and Pink). It certainly shows that the conditions exist that would allow speciation to occur based solely on a single gene locus and provides some strong evidence that this has happened in the case of shell chirality among the water snails, but they do not actually show two distinct non-interbreeding populations arising from a single interbreeding population in their experiments.
TTFN,
WK
This message has been edited by Wounded King, 02-25-2005 06:44 AM
This message has been edited by Wounded King, 02-25-2005 06:50 AM
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