Sympatric speciation or allopatric speciation in disguise?
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Lake Victoria was dry some 12,400 years ago, yet 500 cichlid fish species evolved since then.
Allopatric speciation hypothesis: altering lake levels results in smaller lakes forming, isolating populations.
Sympatric speciation hypothesis: sexual selection drives speciation
Postscript: Human pollution is breaking down reproductive isolation by increasing the cloudiness of the lake waters
We can test these hypotheses using phylogenetic trees. Allopatric speciation predicts similar morphs in different lakes are closely related, whereas sympatric speciation predicts different morphs in the same lake will be closely related.
