Date Time Defeating enemy within: How evolution helps clone fish with their genetic burden According to scientific theories, clonal vertebrates actually have a harder time succeeding than species that reproduce sexually. Clonal fish and still successful: the Amazon molly. | Photo: Davied Bierbach One natural clone is the Amazon molly. A research team led by the Biozentrum of the University of Würzburg with the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) has shown that over hundreds of thousands of years, this small fish has found a way to cope with the challenges of its origin and reproduction. In the course of evolutionary adaptation, traits emerge that tend to be advantageous or disadvantageous to the survival or reproductive success of a species. This happens through natural mutation and subsequent selection. For a new trait to be inherited, it must have a genetic basis. Here, sexual reproduction has an advantage, because the offspring carry equal parts of the genetic information of father and mother, which always makes new combinations possible. Therefore, there are only very few vertebrate species reproducing clonally – via asexual reproduction. In this case, the offspring are genetic copies of the mother – there are no fathers.