Parallel evolution is fascinating. It's when similar changes happen in different groups of the same species. This can happen in their genes or how they look. Scientists have been studying this for a while. But, they still don't fully understand what drives it. One big factor could be pleiotropy. That's when one gene affects many traits. This can make similar changes more likely in different groups.

To dig deeper, researchers looked at fruit flies. They studied 10 groups of Drosophila simulans. These flies were all adapted to the same new temperature. The goal was to see how their genes changed. The results showed something interesting. The more a gene affects many traits, the more likely it is to change in the same way in different groups. This is parallel evolution.

But there's a twist. The original variation in gene activity was less in these cases. This might seem counterintuitive. However, it makes sense when you think about it. Genes that affect many traits are under more pressure. This pressure comes from past selection. It limits how much these genes can vary. So, when a change is needed, these genes respond in a similar way in different groups. This is because they have less room to vary.

The study also found that pleiotropy has a direct effect. Genes that affect many traits can cause related traits to evolve together. This can lead to more parallel evolution. It's like a domino effect. One change leads to another. And another. This can make similar changes more likely in different groups.

So, pleiotropy plays a big role in parallel evolution. It does this in two ways. First, it limits variation in the past. This makes similar changes more likely in the future. Second, it causes related traits to evolve together. This can lead to more parallel evolution. Understanding this can help us see how evolution works. It's not just random. It's shaped by the genes and how they interact.

How Genes Shape Similar Changes in Different Populations

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