Variation in the size and shape of neurocrania of a group of rock-dwelling cichlid fishes
(mbuna) from Lake Malawi, Africa was analysed using principal components and regression
analyses on a set of 24 neurocranial measurements of 86 individuals from 11 species. The
results reveal effective morphological discrimination between species. Most of the structural
variation between species demonstrates positive allometry and represents size-dependent
species differences. Thus, morphological differentiation in these fish may be largely the
result of heterochronic changes in relative growth rates. The vomerine region, however,
exhibited shape differentiation. Distinct groupings, based on vomer shape, are identified.
Foraging behaviour and diet are found to be correlated with this region of the neurocrania.
The correlation of the shape of the vomer and fine-scale resource partitioning suggests that
this structure may be important in the evolutionary success of the group. Also, most structural
shape variation in neurocranial morphology is associated with structural variation in buccal
jaws.