The rock-dwelling cichlids, or mbuna, of Lake Malawi are exceptionally diverse.
Explanations of this diversity have used limited dispersal by the mbuna as the basis
for allopatric models of speciation. However, there have been no studies that have
attempted to define the extent and rates of dispersal of mbuna populations in the field.
The present work took advantage of some translocations in which several species of mbuna
were introduced to the Cape Maclear region of Lake Malawi from elsewhere in the lake.
A detailed series of transects involving observations at four depths was undertaken at
Thumbi West Island to define the distribution of the introduced species. There are large
differences between species in the extent to which they have spread. Some species are now
present all round the island while others have dispersed only a limited distance from the
site of the initial introductions. This survey provides the first comprehensive data set
on the distribution of the introduced species and it raises a number of important questions
regarding their dispersal ability and their likely impact on the endemic community.