Evolutionary biologists find several fish adapt in the same way to toxic
water

Date:
July 8, 2020
Source:
Kansas State University
Summary:
Several species of fish have adapted to harsh environments using
the same mechanism, which brings to question evolutionary chance,
according to a new study.



FULL STORY ========================================================================== Several species of fish have adapted to harsh environments using the
same mechanism, which brings to question evolutionary chance, according
to a study by Kansas State University and Washington State University.


========================================================================== Michi Tobler, associate professor, Ryan Greenway, May 2019 doctoral
graduate, and Nick Barts, doctoral student, all in the Division
of Biology; Joanna Kelley, associate professor at Washington State
University; and many additional collaborators recently published an
article about repeated adaptations to extreme environments in Proceedings
of the National Academy of Sciences.

"We are trying to understand how evolution and adaptation work,"
Tobler said.

"We stumbled across these fish living in this highly toxic water. It
is so toxic that it kills most other living things by binding to an
enzyme in the mitochondria -- the powerhouse of cells -- and shuts
off energy production at the cellular level." The streams have high concentrations of hydrogen sulfide, a gas that is naturally dissolved
in the water. Tobler and his collaborators found at least 10 different
lineages of fish that have adapted to live in the extreme environment.

"Whether or not populations take the same path to adapting to novel environments is a long-standing question in evolutionary biology,"
Kelly said.

"Our research shows that the same pathways have been modified in multiple different species of hydrogen sulfide adapted fishes." All 10 adapted, regardless of location, using the same mechanism: tweaking the enzyme
so the toxicant can't bind to it.

"The cool thing about these enzymes is all organisms have them,"
Tobler said.

"We have them. Fungi have them. Plants have them. It's the universal way
to make energy. Yet, it is this ancient pathway that has been conserved
for so long that is modified in these fish." According to Tobler,
the fish also ramped up an existing detoxification mechanism inside
the mitochondria so they can get rid of the hydrogen sulfide faster and
survive when other non-adapted fish in the same species can't survive
in the toxic water. The multiple lineages of fish with this capability
brings to question a view proposed by evolutionary biologist Stephen
Gould, that if evolution repeated itself, it would lead to different
outcomes every time.

"Thirty years ago, Gould said 'if you could rewind the tape of life,
you would get a different outcome every single time,' meaning that
evolution would not find the same adaptive solutions every time," Tobler
said. "What we actually found in all these lineages -- where the tape
of life has been replayed as they were exposed to the same sources of
selection -- is that evolution actually unfolds in very similar ways. I
think it tells us something very fundamental about how organisms adapt
and that adaptive solutions are possibly limited." The researchers
are able to compare the fish with the adaptation living the toxic water
with ancestors that live in the normal environment because there is not
a barrier between habitats. Tobler said as a consequence of the fish
adapting to the toxic environment, they are actually evolving into a
new species. His graduate students have further research pending.

Tobler's lab is funded by the National Science Foundation and the
U.S. Army Research Office.


========================================================================== Story Source: Materials provided by Kansas_State_University. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Ryan Greenway, Nick Barts, Chathurika Henpita, Anthony P. Brown,
Lenin
Arias Rodriguez, Carlos M. Rodri'guez Pen~a, Sabine Arndt, Gigi
Y. Lau, Michael P. Murphy, Lei Wu, Dingbo Lin, Michael Tobler,
Joanna L. Kelley, Jennifer H. Shaw. Convergent evolution of
conserved mitochondrial pathways underlies repeated adaptation to
extreme environments.

Proceedings of the National Academy of Sciences, 2020; 202004223
DOI: 10.1073/pnas.2004223117 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200708110019.htm

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