Perciformes, Cichlidae) of East Africa, Based on Scale and Squamation Characters
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Journal of Fish Biology (1993) 42, 903-946 A phyletic study on lacustrine haplochromine fishes (Perciformes, Cichlidae) of East Africa, based on scale and squamation characters E. L i p p i t s c h Steingrabenweg 26, A-8044 Graz, Austria (.Received 10 August 1992, Accepted 13 October 1992) Phyletic relations within the haplochromine cichlids of East Africa were investigated vising scale and squamation characters. Within the L. Victoria-Edward-Kivu species flock most of the genera proposed in Greenwood’s revision could be confirmed by this approach. In addition the genera could be interrelated phylogenetically. They form two distinct superlineages comprising several genera each. The genus Axtatoiilapia as conceived by Greenwood is diphyletic. The fluviatile members of the genus form the sister taxon of the L. Victoria-Edward-Kivu flock, while the rest are a subgroup of that flock. The flock seems to be of monophyletic origin. Key words: scale morphology; squamation; phylogenetic relationships; haplochromine fishes; Cichlidae. I. INTRODUCTION When in his classic paper of 1920 C. T. Regan expressed his opinion on Haplochromis, being the ‘ largest African genus ’ (Regan, 1920), he determined the direction for the next 60 years of systematics in East African cichlids. That genus, introduced by Hilgendorf (1888) as a subgenus of Chromis to accommodate a Lake Victoria species with peculiar dentition, became a dumping ground for over 300 species from all over the continent. Regan’s authority prevented any large-scale revision of the complex until 1979. This is the more astonishing as no formal diagnosis for the genus was available, and the only apomorph character uniting the whole assembly (the structure of the pharyngeal apophysis) is found in a number of other genera as well. In two papers, Greenwood (1979, 1980) undertook a ‘ revision of the Haplochromis generic concept omitting, however, the Lake Malawi species. He divided the whole haplochromine assemblage into more than 20 lineages, to which he assigned generic (or, in a few cases, subgeneric) rank. This action was met with considerable reservation among ichthyologists working in the field, even though Greenwood’s competence could not be doubted. The reason for non-acceptance of Greenwood’s revision seems to be at least four-fold. Besides a natural reluctance to give up the convenient catch-all classification, Greenwood’s case was weakened by his own evidence. Only a few years earlier (Greenwood, 1974) he had presented an intrageneric classification of Haplochromis that differed considerably from his later revision, and he had argued in favour of the monophyletic origin of the assemblage. Furthermore it was virtually impossible to assign newly discovered species to Greenwood’s genera on the basis of his key characters (Snoeks et al., 1990; De Vos et ah, 1990). And finally, it seemed impractical to follow a revision excluding the Lake Malawi fishes. 903 0022- II12/93/060903 + 44 $08.00/0 © 1993 The Fisheries Society of the British Isles 904 E. LIPPITSCH In the meantime the L. Malawi haplochromines have been revised (Eccles & Trewavas, 1989), separating all the taxa from Haplochromis and re-establishing or newly describing some two dozen genera. In addition new techniques like protein and enzyme studies (Sage et al., 1984; Verheyen et al., 1985, 1989) or DNA sequencing (Meyer et al., 1990) have revealed close similarities within the L. Victoria-Edward-Kivu assemblage, but significant differences with the L. Malawi taxa. These biochemical methods have proven valuable especially on a higher systematic level. However, while the L. Victoria ‘ species flock ’ contains at least 200 species, only 15 out of 803 positions in two segments of mitochondrial DNA turned out to be variable, the mean number of differences between species being only three (Meyer et al., 1990). This shows that at present investigations on relationships within the assemblage have still to be done by morphological methods. The species considered are rather uniform, however, also with respect to the usual morphological characters. The apomorphic characters worked out by Greenwood (1979,1980) are mainly associated with the trophic apparatus, but it is well-known that those characters are strongly subJect to selection pressure and ecophenotypic effects. Thus, even if apomorphic similarities can be found, it is extremely difficult to assert their synapomorphic status. As Greenwood (1980) expressed it: ‘ Clearly, if sister groups are to be identified,... there is need for... the use of characters other than strictly anatomical ones ’. In previous papers (Lippitsch, 1989, 1990, 1991, 1992) the potential of scale and squamation characters for cichlid systematics have been investigated. The results indicate that there exist a large number of useful characters, that these characters are strongly determined genetically with little intraspecific variation, that many of them are independent from each other, and that their distribution within the Cichlidae is obviously governed by phyletic relationships. The present work investigates scale and squamation characters among haplochromines from the L. Victoria-Edward-Kivu assemblage, assesses character states and polarity, and presents phyletic hypotheses concerning relationships between taxa within the assemblage and those with outside groups. II. MATERIAL AND METHODS This paper investigates only the strictly lacustrine taxa revised by Greenwood (1980). Nevertheless, the choice of species to be studied was made to cover fully the supposed lineages ranked as genera or subgenera in Greenwood’s revision (Greenwood, 1979, 1980) including the fluviatile ones except for Chetia and Pharyngochromis. At least the type species of each genus or subgenus was studied, with the exception of Ctenochromis where the type species (C. pectoralis Pfeffer 1893) was not available for inspection. One or more additional species were included from most of the genera, and a number of species from other genera, especially from L. Malawi, were studied. So a reasonable basis (59 species out of an estimated 250 from genera present in Lakes Victoria, Edward and Kivu and 30 outside species) is available for assessing the distribution of character states and drawing phyletic conclusions. Scale and squamation characters in about 130 further species of cichlids (from Africa, Madagascar, India, and America) have been investigated. A list of specimens used from those species, which have immediate relevance for the present study, is provided in the Appendix. Methods of investigation and the terminology of squamation patterns and scale morphology used were described in previous papers (Lippitsch, 1989, 1990, 1991, 1992). A PHYLETIC STUDY OF HAPLOCHROMINE FISHES 905 Emphasis was laid on documenting as fully as possible details of the squamation pattern and the surface structure of flank scales. Scales were removed from the flank, usually from the second row below the upper lateral line and at least the sixth scale column behind the insertion of the pectoral fin. In part of the BMNH material (especially fishes acquired during the 1950s) the scale surface had deteriorated as a result of storage in formalin, so that some details could not be determined with certainty. In addition many fishes from all museums had been eviscerated and part of the ventral squamation destroyed. For convenience, throughout this paper the term ‘ Victoria-Edward-Kivu assemblage ’ is used to denote the haplochromines of those lakes as well as other water bodies in connection with them. The generic names proposed by Greenwood (1979, 1980) are used for the assemblage and those of Eccles & Trewavas (1989) for L. Malawi fishes. This does not imply full endorsement of either revision. The term haplochromine will be used, again for convenience only, to cover all taxa considered belonging to or being closely related to, Haplochromis by Regan, including Astatoreochromis and the monotypic genera, but excluding the taxa of Greenwood’s Section II (Serranochromis, Sargochromis, Chetia, Pharyngochromis', Greenwood, 1979). II!. SCALE AND SQUAMATION CHARACTERS: STATES, POLARITY, AND DISTRIBUTION During comparative investigations on cichlid scale and squamation characters conducted for 4 years and encompassing about 190 species from over 85 genera, in addition to the usual scale counts, 96 different characters were established, representing about 300 distinguishable character states (Table I). A discussion, of the respective character states and their polarity is given below. Meristic characters, which are usually given in species descriptions, are omitted since in the present context they seem to provide no phylogenetic insight. Polarity assessment in the case of cichlids is particularly difficult. Monophyletic origin of the family has been well established (Stiassny, 1981), and the monophyly of the maJority of African cichlids has been claimed with strong arguments (Cichocki, 1976; Stiassny, 1990, 1991). It is, however, unclear whether the haplochromines in the broadest sense are a monophyletic assemblage, and no outgroups have been delimited. To circumvent these difficulties, character polarity is discussed with respect to the plesiomorphic conditions of what will be called the ‘ African assemblage \ that is most of the African taxa, but excluding Tylochromis, and Helerochromis (and possibly a few others, to be discussed elsewhere). The plesiomorphic character states of this assemblage have been assessed by using Indian, Malagassy, and American taxa as