11th Feb 2015

“Inbreeding Helps African Fish, Scientists Say”

Research on one species of African cichlid has revealed how social factors can sometimes make mating with a close relative evolutionarily advantageous.

Animals in the wild often avoid close kin as mates, as inbreeding causes harmful genes that might otherwise recede into the background to manifest in progeny more often. While animal breeders often practice inbreeding to cultivate desirable traits, they must then cull unfit offspring. However, recent theoretical predictions suggest that, at times, the benefits of inbreeding might outweigh the costs. Now evolutionary biologist Timo Thünken at the University of Bonn in Germany and his colleagues has discovered real-life evidence in support of these predictions. The scientists investigated the African cichlid Pelvicachromis taeniatus, a small monogamous fish that lives in the rivers and creeks of Cameroon and Nigeria. Males occupy caves, while females compete with each other for males.

“We initially wanted to investigate whether P. taeniatus avoid kin as mating partners, because it has been shown in other species that inbred offspring have disadvantages–for example, increased mortality,” Thünken said. “First, we conducted a female choice experiment,” he recalled. This involved aquariums with breeding caves for males and hiding places for rejected females. Against our expectations, females did not avoid brothers, but even preferred them,” Thünken told LiveScience. This proved true in 17 of 23 experiments.

Both parents in the species care for their young to protect them against predators, the researchers noted. This requires high levels of cooperation. Since kinship generally favors cooperation, Thünken and his colleagues theorized related parents did a better job of cooperating than non-kin. Their observations supported their ideas, finding that inbreeding pairs spent significantly more time accompanying their free-swimming young. They also discovered males of inbreeding pairs spent significantly more time guarding breeding caves and were half as likely to attack their mates. The researchers curiously found that inbreeding did not appear to lead to higher rates of harmful gene expression. However, Thünken and his colleagues noted inbreeding might affect traits they have not yet studied, such as thefertility of offspring.

The scientists plan to look next at the level of inbreeding in natural populations of the fish, the fitness consequences of inbreeding and the mechanisms of kin recognition in the species.



“PhD Studentship: The impacts of cooperation on inbreeding depression in the wild”

Isn’t it great, how humans are able to get extended family – parents, siblings, uncles, aunts, in-laws – to help raise our children? Social factors are extremely important for the success of human genes, more than for most species.

This is exactly the kind of research needed. Hopefully there will be more and more like this in the coming years as evolutionary biologists start to realize how badly understood endogamy is. I hope this project gets plenty of funding.



“Scientists Find Mammal Species that Practices Incest Frequently”

This isn’t all that surprising. Every time such evidence comes out, everybody’s flabbergasted because they’re not paying attention to all the other cases. As genetic studies of animal mating patterns improve, we’ll likely find more and more cases like this.

Endogamy is a risky proposition, but everything in life is. The question for everything in evolution is: how risky, and for what reward? Endogamy and exogamy are just mating strategies. How often a species practices endogamy is related to the specific evolutionary circumstances of that species, including the social environment, which determine if and when mating with a close relative is worth the gamble. For some species the cost is too high. For others, it’s not. And for still others, it’s in between. I wonder where humans fall on that spectrum?