Cheaters don't always win: Species that work together do better
Extinction may be prevented by diverse communities of mutually beneficial species

Date:
October 19, 2020
Source:
Syracuse University
Summary:
The sign of a healthy personal relationship is one that is equally
mutual - where you get out just as much as you put in. Nature has
its own version of a healthy relationship. A team of researchers
investigated these interactions, known as mutualisms, and why they
are so critical for healthy environments.



FULL STORY ==========================================================================
The sign of a healthy personal relationship is one that is equally
mutual - - where you get out just as much as you put in. Nature has
its own version of a healthy relationship. Known as mutualisms, they
are interactions between species that are mutually beneficial for each
species. One example is the interaction between plants and pollinators,
where your apple trees are pollinated and the honeybee gets nectar as
a food reward. But what makes these mutualisms persist in nature? If
rewards like nectar are offered freely, does this make mutualisms more susceptible to other organisms that take those rewards without providing
a service in return?

==========================================================================
A team of researchers from the College of Arts and Sciences at Syracuse University, including co-principal investigators Kari Segraves, professor
of biology, and David Althoff, associate professor of biology, along
with postdoctoral researcher Mayra Vidal, former research assistant
professor David Rivers, and Sheng Wang '20 Ph.D., recently researched
that question and the results have been published in this month's edition
of the prestigious journal Science.

They investigated the abilities of simple versus diverse communities
of mutualists, comparing how each deal with cheaters. Cheaters are
species that steal the benefits of the mutualism without providing
anything in return. An example of one of nature's cheaters are nectar
robbers. Nectar-robbing bees chew through the side of flowers to feed
on nectar without coming into contact with the flower parts that would
result in pollination.

The research team wanted to test if having multiple mutualists with
similar roles allows the community as a whole to persist when cheaters
take away the mutualists' resources. The idea was to examine whether
having more species involved in a mutualism, such as many pollinator
species interacting with many different plant species, made the mutualism
less susceptible to the negative effects of cheaters. They also wanted to analyze whether increasing the number of mutualist species allowed all the mutualists to persist or if competition would whittle down the number of mutualists species over time. In essence, the team wanted to understand
the forces governing large networks of mutualists that occur in nature.

A&S researchers tested their ideas by producing mutualisms in the lab
using yeast strains that function as mutualistic species. These strains
were genetically engineered to trade essential food resources. Each
strain produced a food resource to exchange with a mutualist partner. They engineered four species of each type of mutualist as well as two cheater strains that were unable to make food resources.

The researchers assembled communities of yeast that differed both in
the number of species and the presence of cheaters. They found that
communities with higher numbers of mutualist species were better able to withstand the negative effects of cheaters because there were multiple
species of mutualists performing the same task. If one species was lost
from the community due to competing with a cheater, there were other
species around to perform the task, showing that the presence of more
species in a community can lessen the negative effects of cheaters.

"It's similar to thinking about a plant that has many pollinator
species," says Segraves. "If one pollinator species is lost, there
are other pollinator species around to pollinate. If a plant only has
one species of pollinator that goes extinct, the mutualism breaks down
and might cause extinction of the plant." Their results highlight the importance of having multiple mutualist species that provide similar
resources or services, essentially creating a backup in case one species
goes extinct. Segraves compares this phenomenon to the relationship
between retailers and consumers. Communities typically have multiple
banks, grocery stores, restaurants and hospitals to ensure that there
are always goods and services available should something happen to one
company or facility, or, as with COVID today, grocery stores now have
multiple suppliers to fend off shortages.

Segraves says future research will explore the possibility of a mutualist species becoming a cheater. The group is testing if mutualists that
perform the same function might set up an environment that allows
one of those mutualist species to become a cheater since there are
other mutualists around that can fill that role. They predict that the mutualist species that is experiencing the most competition from the
other mutualists will be the species that switches to cheating. They
also hope to determine how the mutualists and cheaters evolved over
time to provide a deeper understanding of the actual changes that led
to differing outcomes in the communities.

The team's research was funded by a $710,000, three-year grant from the National Science Foundation.


========================================================================== Story Source: Materials provided by Syracuse_University. Original written
by Dan Bernardi.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Mayra C. Vidal, Sheng Pei Wang, David M. Rivers, David M. Althoff,
Kari
A. Segraves. Species richness and redundancy promote
persistence of exploited mutualisms in yeast. Science, 2020 DOI:
10.1126/science.abb6703 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201019145551.htm

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