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In our lab meeting we were chatting about divergent selection. I was confused at some point because I wasn't sure what was the meaning of this work in comparison to diversifying/disruptive and other types of selection.

Diversifying selection was coined by J. T. Gulick and I haven't found an interesting answer to compare with our contemporary definition of these terms.

The way I understand this is that, divergent selection is broader and include directional selection as well as disruptive selection. Is that correct?

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I think you are conflating selection and evolution. Diversifying selection is when the variance of a trait in the population increases and even potentially becomes bimodal. This may lead to divergent evolution, i.e. a speciation event. Whereas directional selection still leads to evolution but not necessarily a the formation of a new species.

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  • $\begingroup$ What about disruptive selection? It would be the same thing as divergent selection: the formation of a new species? Also, directional selection could also lead to the formation of a new species through anagenesis. In this case, what would be the differences? $\endgroup$ – M. Beausoleil Apr 27 '17 at 20:28
  • $\begingroup$ I meant diversifying selection not divergent, I've edited my answer as such. Correct directional selection can also lead to speciation through anagenesis. The difference is that when a divergent evolutionary event occurs a new branch is formed (think Darwin's finches). Whereas, with anagenesis the current population changes so much it could longer mate with its "great great grandparents" but because their great great grandparents are longer around we do not consider this to be a branching of the phylogenetic tree. $\endgroup$ – emilliman5 Apr 27 '17 at 20:36
  • $\begingroup$ So, following your answer, both mechanisms (disruptive and directional) could lead to the formation of a new species. To think of it another way, disruptive selection would be that an intermediate trait has a lower fitness, but divergent selection would actually mean that the bimodal trait distribution is actually moving in opposite directions (i.e. opposing directional selection). Is that what you mean? $\endgroup$ – M. Beausoleil Apr 27 '17 at 20:41
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    $\begingroup$ Yes that is a pretty good way to think about it. $\endgroup$ – emilliman5 Apr 27 '17 at 21:24

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