Special Publication (J.L.B. Smith Institute of Ichthyology) no.23

Online version of original print edition of the Special Publication of the J.L.B. Smith Institute of Ichthyology; No. 23The evolution of the cichlid species flock in Lake Malawi has taken place very rapidly and resulted in the proliferation of a large number of species many of which are similar to one another. This has given rise to a situation in which traditional methods of distinguishing species based on preserved specimens are often of limited value. There are many instances of different species having almost identical morphologies, of single populations of one species showing considerable morphological variation and of marked geographical intraspecific variation. Polymorphism is considered not to be as widespread as previously thought, and pronounced random intraspecific colour variation within a population is discounted. Sympatric sibling species may be distinguished by observing behavioural and habitat differences in the field, but no means has been devised for ascertaining whether morphologically and behaviourally similar allopatric forms are specifically distinct. Lack of access to fresh specimens and lack of information on distribution and habitat have resulted in numerous errors appearing in taxonomic works on Lake Malawi cichlids. Great care is needed when attempting scientific descriptions of cichlid species from the African Great Lakes, and it is suggested that such work be left to specialists with knowledge of living and fresh fish in these lakes