Evolution in great lakes has often been both quantitative (many endemic species of
distantly related taxa often being present) and qualitative (outstanding levels of
adaptive radiation having sometimes been achieved). These situations pose many questions,
such as why there are so many endemics and so many superspecialists (and at the same time
often many sibling species), as well as presenting problems relating to such matters as
convergent evolution in different lakes, the possible role of key innovations, the nature
of isolating mechanisms, competition and co-existence in complex communities, the roles
of diverse mutualistic associations, and many others. These rich faunas also provide
particularly favourable opportunities for studying patterns of speciation, while attempts
to elucidate phylogenies in groups such as African cichlid fishes, that have radiated in
several lakes, can be pursued on both a broad scale and at the intralacustrine level
using both recently developed techniques and time-honoured methods. Rates of evolution,
which differ widely between ecologically equivalent taxa in different lakes, have
sometimes been extremely rapid, as attested by both molecular data and evidence from
field studies. Notwithstanding their evolutionary exuberance, these rich faunas are
fragile as demonstrated dramatically by the appalling tragedy that has befallen the
haplochromine cichlid flock of Lake Victoria.