The Adaptive Radiation of Cichlid Fish in Lake Tanganyika: A Morphological Perspective

Tetsumi Takahashi,Stephan Koblmüller

doi:10.4061/2011/620754

Tetsumi Takahashi, Stephan Koblmüller

Open Access

https://doi.org/10.4061/2011/620754

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Abstract

Lake Tanganyika is the oldest of the Great Ancient Lakes in the East Africa. This lake harbours about 250 species of cichlid fish, which are highly diverse in terms of morphology, behaviour, and ecology. Lake Tanganyika's cichlid diversity has evolved through explosive speciation and is treated as a textbook example of adaptive radiation, the rapid differentiation of a single ancestor into an array of species that differ in traits used to exploit their environments and resources. To elucidate the processes and mechanisms underlying the rapid speciation and adaptive radiation of Lake Tanganyika's cichlid species assemblage it is important to integrate evidence from several lines of research. Great efforts have been, are, and certainly will be taken to solve the mystery of how so many cichlid species evolved in so little time. In the present review, we summarize morphological studies that relate to the adaptive radiation of Lake Tanganyika's cichlids and highlight their importance for understanding the process of adaptive radiation.

Highlights

With an estimated number of about 3000 species, distributed from Central and South America, across Africa to Madagascar and southern India, cichlid fishes (Cichlidae) represent the most species-rich family of vertebrates, accounting for about 10% of today’s teleost diversity [1, 2]. Throughout their distribution range cichlids have repeatedly demonstrated their capacity of forming adaptive radiations—explosive speciation with niche partitioning, generating an outstanding variation of body shapes, colour patterns and behaviour, and an enormous diversity of trophic and ecological specializations [4,5,6], which attracted numerous evolutionary biologists and established them as one of the prime model systems in evolutionary biology (e.g., [7,8,9]), but the greatest diversity of cichlid fishes is found in the East African Great Lakes [2]
Whereas isometric growth of the lower pharyngeal jaw was reported for the Lake Tanganyika cichlid Lamprologus ornatipinnis [69], a species that predominantly feeds on invertebrates and does not experience a drastic shift in feeding habits throughout ontogeny, Hellig and colleagues [70] showed that an allometric change in ontogenetic lower pharyngeal jaw development of Lepidiolamprologus elongatus, a top predator in the shallow rocky habitat of Lake Tanganyika, coincides with the dietary shift to exclusive piscivory (Figure 4)
This observation might indicate that distinct allometry is correlated with strong specialization, but it remains to be tested whether this is a general phenomenon in trophic specialists, what is the genetic basis of such morphological changes, and to what extent differential gene expression producing differences in morphology contributes to the astounding diversity of cichlid fishes in Lake Tanganyika

Summary

Introduction

With an estimated number of about 3000 species, distributed from Central and South America, across Africa to Madagascar and southern India, cichlid fishes (Cichlidae) represent the most species-rich family of vertebrates, accounting for about 10% of today’s teleost diversity [1, 2]. Tylochromis polylepis and O. tanganicae colonized the lake only recently, establishing themselves in an already mature adaptive radiation [25, 31] Excluding these species, the Lake Tanganyika cichlid species flock comprises at least six major lineages [27]. The Tropheini, one of the endemic mouth-brooding tribes, were shown to be nested within the haplochromines, the most species-rich lineage that includes the species flocks of the remaining East African Great Lakes and the majority of the northern, eastern, and southern African riverine cichlid species but originated in the course of the primary Tanganyika radiation [29, 30]. Mitochondrial phylogenies have been and are still used as proxies of species trees in comparative approaches to study the interaction and evolution of biological traits in a phylogenetic context (e.g., [54,55,56,57]), potentially introducing an error in inferred evolutionary patterns

Adaptive Morphology

Conclusions

Findings

Increasing proportion of fish diet