A contribution to the ecology and systematics of the genus Petrotilapia (Pisces : Cichlidae) in Lake Malawi
- Authors: Marsh, Alan Clive
- Date: 2013-03-20
- Subjects: Cichlids -- Nyasa, Lake , Petrotilapia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5355 , http://hdl.handle.net/10962/d1009513 , Cichlids -- Nyasa, Lake , Petrotilapia
- Description: The nominal species Petrotilapia tridentiger Trewavas, a rock-frequenting fish from Lake Malawi, occurs in three distinct male and female colour forms at Monkey Bay. Field observations on courtship and aggression indicate that the three colour forms are distinct species. The taxonomy of the three species of Petrotilapia that occur at Monkey Bay is revised. R. tridentiger is redescribed and two new species, P. genalutea and P. nigra, are described. The three species are very similar morphologically and are considered to be sibling species. The only morphological character which reliably separates the three sibling species is live coloration: Live coloration is considered to be an important component of the specific mate recognition systems in Petrotilapia species. The coloration of a further fourteen forms of Petrotilapia is described and it is suggested that these forms are valid species. Space resource partitioning plays an important role in facilitating the coexistence of Petrotilapia sibling species. Space is partially partitioned in terms of depth range. In shallow water, where all three species are sympatric, there are differences in the feeding sites used by the various Petrotilapia forms. Changes in niche breadth and overlap, which are associated with changes in the abundance of epilithic algae, indicate that competition for feeding space occurs between the three Petrotilapia species. The Petrotilapia species partition their resources according to a social dominance hierarchy. Dominant forms, such as territorial males, R. tridentiger females and schooling R. genalutea females, have access to rich food supplies which occur within the territories of certain highly aggressive Pseudotronheus species. are facultative and opportunistic .feeders. Petrotilapia species Speciation in allopatry is considered to be the mechanism which adequately explains the current diversity of the genus Petrotilapia. The importance of an integrative approach to future systematic and ecological research on Lake Malawi cichlids is stressed. , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
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An ecological study of territoriality in four Cichlid species resident on rocky shores near Monkey Bay, Lake Malawi
- Authors: Sharp, Bradley John
- Date: 1982
- Subjects: Cichlids -- Nyasa, Lake , Cichlids -- Behavior
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5340 , http://hdl.handle.net/10962/d1005927 , Cichlids -- Nyasa, Lake , Cichlids -- Behavior
- Description: This study centres on a diverse assemblage of epilithic algal grazing fish (17 cichlids and 2 cyprinids) found on the rocky shores near Monkey Bay, Lake Malawi. Diet overlap among these species is large, but competitive exclusion is apparently avoided by the species having different feeding structures, behaviour and distribution on the shore. In many respects the ecology and behaviour of the cichlid fishes inhabiting the rocky zones of Lake Malawi parallel those of coral reef fish. In both communities there are species which are highly territorial, resulting in resource subdivision and, in some cases, the development of algal gardens. As this behaviour has not been previously reported for cichlid species, this thesis describes the territoriality of the rock-dwelling cichlids of Monkey Bay, Lake Malawi, and poses three specific questions: 1. What is the function of territoriality? 2. How do the territorial species subdivide the space resource? 3. What prevents one species taking over all the available space? It is suggested that interspecific territoriality evolved in response to a shortage of food, and, at present, serves principally to defend an algal garden i.e. a food supply of high standing crop. The species studied are extremely site specific. The rocky shore is subdivided among the four species according to the rock configuration, size, algal mat composition and position on the shore, of the available sites. An experimental study of the space utilization of the two common territorial species, referred to as 'Pseudotropheus orange cheek' and 'Pseudotropheus aggressive', showed that suitable territory sites are in short supply and that these species are in competition for some sites. These results do not support those of Fryer (1959) who suggested that a superabundance of food enabled fish to coexist by sharing the same food resource. Indeed it now appears that a shortage of food may have been a major driving force during the recent evolution of the species studied.
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