Mating and Parental Care in Lake Tanganyika's Cichlids
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SAGE-Hindawi Access to Research International Journal of Evolutionary Biology Volume 2011, Article ID 470875, 20 pages doi:10.4061/2011/470875 Review Article Mating and Parental Care in Lake Tanganyika’s Cichlids Kristina M. Sefc Department of Zoology, Karl-Franzens University Graz, Universitatsplatz¨ 2, 8010 Graz, Austria Correspondence should be addressed to Kristina M. Sefc, [email protected] Received 30 December 2010; Revised 22 March 2011; Accepted 2 May 2011 Academic Editor: Tetsumi Takahashi Copyright © 2011 Kristina M. Sefc. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Cichlid fishes of Lake Tanganyika display a variety of mating and parental care behaviors, including polygamous and monogamous mouthbrooding and substrate breeding, cooperative breeding, as well as various alternative reproductive tactics such as sneaking and piracy. Moreover, reproductive behaviors sometimes vary within species both in space and in time. Here, I survey reports on mating and parenting behaviors of Lake Tanganyika cichlid species and address the evolution of mating and parental care patterns and sexual dimorphism. Notes on measures of sexual selection intensity and the difficulties of defining mating systems and estimating selection intensities at species level conclude the essay. 1. Introduction The comprehensive synopsis of parental care and mat- ing systems of Lake Tanganyika’s cichlids by Kuwamura Mating and parental care patterns are shaped by evolutionary [19] has become a widely used source of information to mechanisms, and in turn, reproductive behavior bears on researchers in this field. Kuwamura classified the mating the course of evolution. Both directions of this feedback systems of LT cichlid species into monogamy, characterized loop have received attention in theoretical and empirical by biparental care or consistent spawning with the same studies (e.g., [1–3]), but a number of issues around the partner, harem polygyny with the male territories including interplay of sexual selection, ecology, mating, parenting, and those of several females, male-territory-visiting polygamy, phenotypic divergence remains controversial (e.g., [1, 4, 5]). in which females visit the males’ territories for spawning Hypotheses have been tested in taxa ranging from yeast to but do not form pair bonds, and nonterritorial polygyny, in humans [6, 7],withastrongcasemadeforfishesasmodels which males defend spawning sites only during courtship. to study sexual selection and parental care by Amundsen [8]. All cichlids perform brood care, either by mouthbrooding The opportunities offered by fishes are manifold: different or by guarding eggs and fry (substrate breeding), or, as in ecological backgrounds, a variety of life histories, including several species, by a mixture of both, when mouthbrooding sex change and alternations of reproductive tactics as well of eggs and small fry is followed by guarding of free- as fixed behavioral polymorphisms, external and internal swimming fry. Kuwamura [19, 20] further classified the fertilization, brood care ranging from none to biparental and parental care patterns of LT cichlids into biparental guarding even cooperative, and different levels of sexual dimorphism in monogamous substrate breeders, maternal guarding in and speciation rates, allow to address consequences of sexual haremic substrate breeders, mouthbrooding (sometimes selection as well as factors influencing it. Except for sex followed by guarding) in monogamous species, and maternal change (but see [9]) and internal fertilization, cichlid fishes mouthbrooding in polygamous species. True to the title provide a broad width of study topics at varying phylogenetic of his article [19], Kuwamura developed a model of the levels. In particular, the diversity in morphology, ecology, evolutionary transitions between parental care patterns in LT mating, and parenting behavior of the Lake Tanganyika cichlids and discussed the forces and opportunities driving (LT) cichlids matches their phylogenetic diversity [10], and these changes. A list of species with parental care, nest site, their potential for comparative phylogenetic studies has been and mating system type completes his compilation. Since tappedinvariouscontexts[2, 3, 11–18]. the publication of Kuwamura’s article in 1997, further field 2 International Journal of Evolutionary Biology and laboratory work and, more recently, genetic parent- Table 1: Alphabetical list of genera mentioned in the text and their age analyses have unearthed even more detail about the tribal association according to Koblmuller¨ et al., [10]. Lamprologini reproductive behavior of LT cichlids. In particular, attention and Boulengerochromini are substrate breeders, all the other LT to alternative reproductive tactics (especially cooperative cichlids are mouthbrooders. breeding) has ever been increasing, and a small number of Genus Tribe selected species became prominent subjects to address the Altolamprologus Lamprologini ff causes, functions, and mechanisms of di erent behavioral Asprotilapia2 Ectodini options. The role of natural selection in the evolution of Aulonocranus Ectodini sexual size dimorphism in shell breeding cichlids has been established by a series of studies. Finally, recent molecular Boulengerochromis Boulengerochromini phylogeny-based approaches to the evolution of mating Chalinochromis Lamprologini and parental care patterns provided detailed reconstructions Ctenochromis horei1 Tropheini of behavioral character transitions, with good support for Cyathopharynx Ectodini Kuwamura’s original model. Cyphotilapia Cyphotilapiini The present paper collects both pre- and post- 1997 Cyprichromis Cyprichromini data on LT cichlid mating and parenting behavior, then Eretmodus Eretmodini summarizes studies addressing the evolution of mating and Gnathochromis pfefferi1 Tropheini parenting patterns in cichlids and of sexual dimorphism Haplotaxodon Perissodini in certain LT cichlid species, and concludes with notes on Julidochromis Lamprologini the estimation of sexual selection intensity. Intraspecific 3 variation in reproductive behavior, the employment of var- Lamprologus Lamprologini 3 ious alternative tactics, and finally behaviors, which cannot Lepidiolamprologus Lamprologini unambiguously be assigned to one of the defined mating Limnochromis Limnochromini system categories (e.g., the combination of lek and resource- Microdontochromis2 Ectodini defense mating system characteristics by Simochromis pleu- Neolamprologus3 Lamprologini rospilus [21]), render the classification of species-level mating Ophthalmotilapia Ectodini systems difficult, and no attempt is made here to update Paracyprichromis Cyprichromini Kuwamura’s categorization of species by mating or parenting Perissodus Perissodini behavior. Petrochromis Tropheini Plecodus Perissodini Pseudosimochromis Tropheini 2. Substrate Breeding and Mouthbrooding Reganochromis Limnochromini Substrate breeders (Lamprologini and Boulengerochromini, Simochromis Tropheini Table 1) attach their adhesive eggs to different solid surfaces Spathodus Eretmodini meeting species-specific requirements in orientation, angle, Tanganicodus Eretmodini and seclusion. Hatched embryos are often transferred in Telmatochromis Lamprologini the female’s mouth to rock crevices or pits [22–25]. Larvae Triglachromis Limnochromini of some species remain close to the substrate and spread Tropheus Tropheini horizontally while those of others expand their area into the Variabilichromis3 Lamprologini water column [23]. Brood care includes egg cleaning and Xenotilapia Ectodini fanning, as well as defense from predators. The eggs and 1The genus names Ctenochromis and Gnathochromis are shared with species fry of mouthbrooders are incubated in the buccal cavity of belonging to other tribes [10, 38]. one or both of their parents. Advantages of mouthbrood- 2within Xenotilapia [38]. ing include protection from predators and environmental 3Current generic assignments of Lamprologus, Neolamprologus, Lepidio- stressors [26], the possibility to breed independently of the lamprologus, and Variabilichromis species may differ from those in earlier availability of suitable surfaces for egg attachment [27], publications. and the possibility to move fry to suitable habitats for release [26], but also incurs considerable costs (see below). Egg and clutch sizes differ between substrate breeders and mouthbrooders. The eggs of the mouthbrooders are typically [28, 32, 33]. Time to hatching is positively related to egg quite large with diameters up to 7 mm (except for some size [11] and takes three to five days after fertilization in biparental mouthbrooders [28]), and clutch size is naturally substrate breeders [23, 32, 34, 35] and three to eight days restricted by the capacity of the buccal cavity to <50–80 postfertilization in mouthbrooders [36, 37]. The duration of eggs depending on egg size and brooder body size [28– posthatching brood care is often longer in substrate breeders 31]. In contrast, eggs of substrate breeders are smaller with than in mouthbrooders and varies widely among species of diameters around 2 mm [28], and clutch sizes vary widely both groups (see below). between species, ranging from 10–20 eggs in the small shell In all LT cichlid species, females invest in brood care, breeders to hundreds and thousands of eggs in larger species either with or without male