Background information

A super cute cichlid from Lake Tanganyika. Its latin name is Eretmodus cyanostictus. This species lives in shallow waters. Photo: Simon Hornung

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The significance of Tanganyikan cichlid fishes

For those who appreciate some biological background information.

Adaptive radiation

Some biologists dedicate their scientific projects (in many cases their whole life) to the cichlids of Lake Tanganyika and this is for a very good reason: these cichlids represent one of the largest and most impressive adaptive radiation on our planet. In the following, I explain to you what “adaptive radiations” are and why they are so exciting to investigate.

Maybe some of you have heard about the popular Darwin finches from the Galapagos islands, eighteen species that share one common ancestor, which colonised the islands long time ago. Although these species are closely related to each other, their appearance differs according to their respective ecological niche (where they live, what they eat etc.). One striking example are their beaks. A species with a big and strong beak is able to break hard seeds, while a species with a long and thin beak can access nutritious parts of cactuses. So the beak of each species is specialised to exploit a certain food resource.

When Darwin arrived on the Galapagos islands in 1835, these finches served as a very illustrative example of how natural selection shapes organisms to fit their environmental conditions. Until today, they serve as a textbook example for adaptive radiations. In a nutshell, we speak of an adaptive radiation when a multitude of closely-related species evolved rapidly from a common ancestor as a consequence of adaptation to different ecological niches.

Back to the cichlids

Although the adaptive radiation of Darwin finches is one of the most popular examples, the massive radiation of cichlid fishes in Lake Tanganyika is much bigger. With about 240 species, the Tanganyikan cichlids represent one of the most impressive adaptive radiations known today.

Why studying adaptive radiations?

One very important reason to study adaptive radiations is to increase our understanding of speciation, which is the process responsible for our breathtaking biodiversity. In adaptive radiations, a lot of speciation events took (and often still take) place within a rather short period of time. But why do some groups of organisms radiate while others don’t? What makes some groups so prone to speciate while others remain unchanged for millions of years? To find answers to these fundamental questions still ranks amongst the most important endeavours in evolutionary biology.

Sunset over Lake Tanganyika, Kalambo Falls Lodge, Zambia. Foto: Carolin Sommer-Trembo
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