TAXONOMIC STUDY OF THE GENUS PETROTILAPIA TREWAVAS 1935 (TELEOSTEI: CICHLIDAE) FROM LAKE MALAŴI, AFRICA
Open Access
- Author:
- Lundeba, Mary
- Graduate Program:
- Wildlife and Fisheries Science
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- July 07, 2009
- Committee Members:
- Jay Richard Stauffer Jr., Dissertation Advisor/Co-Advisor
Jay Richard Stauffer Jr., Committee Chair/Co-Chair
C Paola Ferreri, Committee Member
Walter Matthew Tzilkowski, Committee Member
Ke Chung Kim, Committee Member
A Konings, Committee Member - Keywords:
- melanin pattern
cichlid
mbuna
Petrotilapia
Malawi
radiation - Abstract:
- Lake Malaŵi is the southernmost of the East African Rift Lakes and harbors about 850 cichlid species of which less than 500 have been scientifically described. One of the genera of cichlid fishes is Petrotilapia, which contains the largest mbuna (rock-dwelling cichlids) of Lake Malaŵi. Petrotilapia species are characterized by broad fleshy lips that are densely covered with slender teeth that are visible even when the mouth is closed. The members of the genus Petrotilapia have been divided into three groups namely the P. tridentiger, the P. genalutea, and the P. nigra group. The members of the P. tridentiger group are mainly found in the wave-washed upper rocky habitats, while those of the P. genalutea group inhabit the sediment-rich and intermediate habitats. The P. nigra group contains the largest number of species that inhabit the deeper rocky environments; this group prefers sediment-free rocky habitats. The three Petrotilapia groups are also distinguished by female melanin pattern. The pattern in females of the P. tridentiger group consists of indistinct vertical bars. Females of the P. genalutea group are characterized by two rows of spots on the flank, with the lower row consisting of a few large blotches. Females of P. nigra group often have a yellow or golden background color and a pattern consisting of two horizontal rows of dots of about the same size, with the ones of the mid-lateral row slightly larger. A pattern of, sometimes indistinct, vertical bars is superimposed on the two horizontal rows of dots. Five hundred and sixty newly collected Petrotilapia specimens were evaluated. New species of Petrotilapia were diagnosed and described by investigating morphological and meristic differences among populations. Petrotilapia populations were compared on the basis of locality, species complex (Petrotilapia tridentiger, Petrotilapia genalutea, or Petrotilapia nigra group), and markings (presence or absence of a black band in the dorsal fin). Differences in morphology were analyzed using sheared principal component analysis (SPCA) of the morphometric data and principal component analysis of the meristic data. Differences among species were illustrated by plotting the second sheared components of the morphometric data against the first principal component of the meristic data to maximize the amount of separation. If the mean multivariate scores of the clusters formed by the plots were significantly different along one axis independent of the other, a Duncan Multiple Range Test (DMRT) (p<0.05) was used to determine which clusters differed from each other. If the clusters were not significantly different along either axis, then a multivariate analysis of variance (MANOVA), in conjunction with a Hottelling-Lawley trace was used (p<0.05). Five populations of Petrotilapia were found to be different from all other populations as well as from described species and were described as new species. Newly described species include Petrotilapia xanthos from Gallireya Reef, Petrotilapia mumboensis from Mumbo and Thumbi West islands, Petrotilapia pyroscelos from Mkanila Bay, Chizumulu Island, Petrotilapia flaviventris from Same Bay, Chizumulu Island, and Petrotilapia palingnathos from Mkanila Bay, Chizumulu Island; this brings the total to 10 described Petrotilapia species. I determined Petrotilapia ‘ruarwe’ from Kakusa and Mbowe Island as conspecifics with Petrotilapia microgalana from Nkhata Bay. There was no morphological difference between Petrotilapia sp. ‘mumbo yellow’ from Mumbo Island and P. nigra from neighboring Thumbi West Island. I, therefore, considered P. sp. ‘mumbo yellow’ a geographical variant of P. nigra. There may be five more undescribed species in the genus Petrotilapia.