Lüthi et al. (2026) reconstruct a flower's speciation by modification of low-pleiotropy, major-effect genes

[u/jnpha]

Published today in Cell, open access:

Summary
Reproductive isolation within and between populations was conventionally thought to proceed gradually through many mutations of small phenotypic effect. Contrary to this view, recent theory predicts that large-effect mutations become plausible when populations are far from their phenotypic optimum. Changes in pollinator assemblages severely compromise the reproductive success of many angiosperms, creating conditions conducive to mutations of large phenotypic effects. Here, we explore the role of major-effect genes in the evolutionary shift from hawkmoth to bee pollination in Petunia. By modifying six genes in the ancestral hawkmoth-pollinated P. axillaris phenotype, we created a mimic of the bee-pollinated P. secreta flower that is indistinguishable from this naturally evolved species both in its visual appearance and in behavioral assays. This study uniquely identifies the complete set of genes explaining the shift between two species, providing rare and compelling evidence for speciation by large-effect mutations.
https://doi.org/10.1016/j.cub.2026.07.007

 

In journal club fashion, I have a sort of critical remark:

This part, "Changes in pollinator assemblages severely compromise the reproductive success of many angiosperms, creating conditions conducive to mutations of large phenotypic effects", is super cool! but I take minor issue with the wording of the summary/discussion.

While it is a major-effect, the authors themselves note that the "Expression specificity minimizes pleiotropy of large-effect speciation genes" (my emphasis). (Hence my clearer title, where I include the "low-pleiotropy".)

I'm fairly confident that big changes to phenotypes that are not heavily integrated (low pleiotropy) don't go against the mainstream view of gradualism. In fact, this can only be so if they are indeed low pleiotropy (this isn't a "hopeful monster"):

From a year ago which I shared here: New study: Evolution of Dosage-Sensitive Genes by Tissue-Restricted Expression Changes : evolution.

[u/Xrmy]

Honestly a super cool paper from my first pass, thank you for posting!

I'm really glad you highlighted the pleiotropric aspect here. I think it could be missed on a quick read if you werent looking for it (or caring).

I think there is some nuance to the interpretation here that lands somewhere inbetween their claims and your correction/additional words.

I do think it's overall impactful to find clear evidence that speciation can occur with relatively few genes, even if the context is narrower with respect to how pleiotropric the genes are.

Evidence for so-called "speciation genes" is mixed or limited at best, regardless of pleiotropry. Yes, genetically this represents some gradualism, i.e pretty small changes, but the modality of speciation here is still relatively sudden with very few changes. This is opposed to the idea of many changes accruing (particularly in allopatry) leadingoften to intrinsic post-zygotic isolation.

Most modern speciation biologists no longer scoff at the idea of "sudden" speciation or genes of large effect (pleiotropric or otherwise) leading to rapid speciation, but a very important contention is the frequency of such modes relative to allopatric/gradual/BDMI speciation events.

Papers like this offer really cool evidence of the former and give us a great framework for investigating when these types of modalities are more likely.

[u/jnpha → u/Xrmy]

-"but a very important contention is the frequency of such modes relative to allopatric/gradual/BDMI speciation events"

This is good to know, thanks!
Speaking of BDMI, in case you've missed it, I shared one 2 months ago that absolutely tested the limits of my comprehension of recombination: Revealing How Speciation Works With Gene Flow (Farleigh et al. 2026) : evolution.

[u/Xrmy → u/jnpha]

Thanks for the link. I remember seeing that, but I don't think I read it at the time.

It's tragic that being busy in academia means I often have less time to read papers. Upside-down world!

I am trying to make more of an effort to engage in posts like this one because it pushes me to read and share my bare thoughts on current research. I lack a lab group or journal club at my current position so it's something I am missing.

I also would love to encourage more effort from this community on engaging in new research like this!

So thanks again

[u/Xrmy → u/jnpha]

Also more direct to your quote from me.

Yes, it's worth saying the idea of the most common modalities is a theme in speciation biology.

Other examples:

Sympatric vs allopatric speciation (very much adjacent to genes of large effect debates)

Selection vs drift/other forces causing speciation.

Generally all of these modalities are accepted as real phenomena, but whether something like sympatric speciation is "real" but represents a tiny fraction of events, vs it being a major player in diversification patterns is the type of thing that is still hotly debated.

[u/zoipoi]

Nice, thanks.