Abstract
A taxonomic revision of the cichlid genus Astatoreochromis is presented. Eighteen meristic and 23 morphometric measurements were taken on 185 individuals, including type specimens. While fin counts separate populations from the Lake Victoria region (Astatoreochromis alluaudi) from those of the Rusizi and Malagarazi rivers in the Lake Tanganyika basin (A. vanderhorsti and A. straeleni respectively), clear differentiation was not detected between the latter two. Mann-Whitney U-tests on specimens of comparable size from the two Tanganyika populations revealed significant differences in specimens < 75 mm SL, mainly in pharyngeal jaw proportions, but also in some other measurements on the head and body. However, these differences were not detected in specimens > 75 mm SL and Astatoreochromis vanderhorsti is herein considered a junior synonym of A. straeleni. A redescription of the two valid species of Astatoreochromis, A. alluaudi and A.straeleni, is provided.
Highlights
By far the highest diversity of cichlids occurs in the east and central African lakes Tanganyika, Victoria and Malawi, where they have speciated in great profusion (Stiassny & Meyer 1999; Snoeks 2001)
A first PCA on 22 meristics for all examined specimens revealed the presence of two major groups with minor overlap, one situated mainly on the negative part of the first axis and containing the Lake Victoria basin specimens, and the other, mainly situated on the positive part of the first axis, containing the Lake Tanganyika basin specimens (Fig. 2A)
A PCA performed on 23 log-transformed measurements did not result in a good separation between the Lake Victoria and the Lake Tanganyika basin populations (Fig. 2B)
Summary
By far the highest diversity of cichlids occurs in the east and central African lakes Tanganyika, Victoria and Malawi, where they have speciated in great profusion (Stiassny & Meyer 1999; Snoeks 2001). Later, Poll (1974) reported eight additional specimens from the Rusizi River and redescribed the species Based on these new specimens, which had 3-4 anal spines, rounded caudal fins and shared close similarities in colour pattern and the arrangement of anal ocelli with A. alluaudi, Poll (1974) reallocated H. straeleni to the genus Astatoreochromis. Hoogerhoud (1986) agreed with this reallocation but stipulated that the close resemblance of A. straeleni and A. vanderhorsti raises questions as to their validity as different taxa, a view later shared by De Vos et al (2001a) To clarify this situation, a detailed morphometric study of the three nominal Astatoreochromis species was conducted, and the results are presented below
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