Gerbilliscus has been in recent years the subject of new molecular and karyological investigations that shed new light on the evolutionary processes of this taxon. However, the patterns of phenotypic diversification of Gerbilliscus remain poorly understood. Furthermore, the molecular phylogenetic analyses posed new questions concerning the systematics and taxonomy of the whole genus and revealed the possible occurrence of cryptic species and hence the need to carry out a taxonomic revision. We used geometric morphometrics to investigate the adaptive value of morphological changes and to elucidate the systematic relationships and taxonomic status of the Gerbilliscus species of east Africa. Our results show concordance between morphological and genetic species boundaries. However, the observed morphological differences appear not only related to hereditary characters. In fact, the correlation with the climatic variables suggests an adaptive value of shape changes related to different trophic resources availability. Finally, discriminant analysis of the eastern Africa Gerbilliscus species highlight the distinctiveness of G. vicinus, clearly separated from G. robustus and G. nigricaudus. (C) 2009 Deutsche Gesellschaft fur Saugetierkunde. Published by Elsevier GmbH. All rights reserved.