Abundance, distribution, and territory areas of rock-dwelling Lake Tanganyika cichlid fish species

Hydrobiologia (Impact Factor: 2.28). 12/2008; 615(1):57-68. DOI: 10.1007/978-1-4020-9582-5_5


Lake Tanganyika, the second-oldest and second-deepest lake in the world, harbors an impres-sive cichlid fish fauna counting about 250 endemic species that are characterized by a great level of ecological, morphological, and behavioral specializa-tion. This study describes and compares cichlid fish communities at two rocky shores with differential human impact in the south of Lake Tanganyika. Species inventories and depth-dependent abundances were elaborated. About 41 and 46 sympatric cichlid species were recorded in the two study sites, respec-tively. Variabilichromis moorii was the most abundant species (29–60% of total number of fishes), followed by Aulonocranus dewindti (3–19%), Tro-pheus moorii (12%), Ophthalmotilapia ventralis (4–10%), Eretmodus cyanostictus (6–11%), and Cyathopharynx furcifer (0.01–9%). All other species had abundances below 5%. It further emerged that large cichlids such as Petrochromis species, Cyatho-pharynx furcifer, and Lobochilotes labiatus were very rare at one location, with frequencies of 0.55% or less. Territorial sizes of three particularly abundant species, Variabilichromis moorii, Aulonocranus dew-indti, and Tropheus moorii, were assessed by behavioral observations. We distinguished between territorial core areas and total defended area, yielding average core areas between 0.4 (V. moorii) and 1.6 m 2 (T. moorii), and total defended areas averag-ing for each species between 1.6 (V. moorii) and 5.0 m 2 (A. dewindti) with no significant differences between the two study sites. The data on individual densities are also relevant for evolutionary studies, in that they allow more accurate calculations of effec-tive population sizes.

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    • "After spawning, females abandon their mate for maternal mouthbrooding (Yanagisawa and Nishida 1991). Territory quality influences male mating success (Yanagisawa and Nishida 1991; Hermann et al. 2015), and competition for territories ensues from the high density of Tropheus in the rocky littoral of Lake Tanganyika (e.g., Sturmbauer et al. 2008). "
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    ABSTRACT: Assortative mating promotes reproductive isolation and allows allopatric specia-tion processes to continue in secondary contact. As mating patterns are determined by mate preferences and intrasexual competition, we investigated male–male competition and behavioral isolation in simulated secondary contact among allopatric populations. Three allopatric color morphs of the cichlid fish Tropheus were tested against each other. Dyadic male–male contests revealed dominance of red males over bluish and yellow-blotch males. Reproductive isolation in the presence of male–male competition was assessed from genetic parent-age in experimental ponds and was highly asymmetric among pairs of color morphs. Red females mated only with red males, whereas the other females performed variable degrees of heteromorphic mating. Discrepancies between mating patterns in ponds and female preferences in a competition-free, two-way choice paradigm suggested that the dominance of red males interfered with positive assortative mating of females of the subordinate morphs and provoked asymmet-ric hybridization. Between the nonred morphs, a significant excess of negative assortative mating by yellow-blotch females with bluish males did not coincide with asymmetric dominance among males. Hence, both negative assortative mating preferences and interference of male–male competition with positive assorta-tive preferences forestall premating isolation, the latter especially in environments unsupportive of competition-driven spatial segregation.
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    • "Males and females actively defend separate feeding territories in the shallow littoral of Lake Tanganyika, East Africa, and browse on epilithic algae. The densely packed, contiguous territories range in size from 0.25 to 4 m 2 (Takamura 1984; Sturmbauer et al. 2008), and observations of frequent replacements and territory expansions upon removal of territory holders (Yanagisawa and Nishida 1991) suggest strong intraspecific competition (Grant 1997). Tropheus are maternal mouthbrooders. "
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    • "Tropheus lives at rock and cobble shores where it inhabits a wide range of water depths, sometimes down to 40 m, but its highest density is between the depths of 0.5 and 5 m (Kohda and Yanagisawa, 1992; Sturmbauer et al., 2008). The genus is highly specialized and occupies the trophic niche of mainly browsing on filamentous algae, whereas other genera utilize different resources in this complex littoral species community (Sturmbauer et al., 1992; Konings, 1998). "
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