Spice of life

Fish called zebra cichlids are only found in Lake Malawi in Africa. What makes them special is that males come in a variety of technicolour coats, which is extremely unusual in a single species. They certainly weren’t evolving to hide from predators, or adapting to local conditions. To find out more, Steve Leonard puts the larger, more colourful males in choice chambers while allowing the little brown females to swim in with the male they fancy most. The tests show that even females of the same species have different ideas about what is sexy. Some prefer white males, some yellow, others blotchy, and so on. This explains why zebra cichlid males come in so many different colours. But how does that help to create new cichlid species? The answer is that if a group of females gang together and decide that one colour is now highly desirable, they will then only mate with those particular males. This preference is passed on to their daughters and an entirely separate breeding group is formed over generations until eventually a new type of cichlid is produced. So Girl Power leads to amazing variety and ultimately new species. Lake Malawi and the other African great lakes started out with just a handful of cichlid species. Now they are home to one in ten of all kinds of freshwater fish on the planet. They are now home to an incredible 1,700 cichlid species, all fashioned by female choice. This is the greatest explosion of new species ever discovered and is all driven by the relationship between females and their males.

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