Biodiversity can offer protection to weakies species

If you pit a pair of gladiators, one strong and one weak, against each other 10 times the outcome will likely be the same every time: the stronger competitor will defeat the weak. But if you add into the field additional competitors of varying strength levels, even the weakest competitors might be able to survive -- if only because they're able to find a quiet corner to hide.

The same is true in the natural world, where in some ecosystems species compete with others for the space to survive and reproduce, according to a long-held scientific theory.

In a new study Yale researchers illustrate that, in the case of fungal communities, maintaining a diverse collection of species indeed not only safeguards weaker species but also protects the genetic diversity of the larger community.

Or, as the researchers suggest, biodiversity begets biodiversity. Understanding this phenomenon, they say, will help in efforts to protect some of the world's most threatened ecosystems, including coral reefs.

For the study, the researchers observed interactions between 37 distinct types of wood-decay fungi, which are any species of fungi that grow on dead wood. Unlike other plants, fungi species grow toward other species and compete for space. "They're much more like territorial carnivores," said Dan Maynard, a doctoral student at the Yale School of Forestry & Environmental Studies (F&ES) and lead author of the study. . "They have a territory from which they gather resources, and they want to protect that territory very strongly."

In a series of experiments the researchers placed pairs of fungal species on opposite ends of a 10-centimeter Petri dish -- more than 600 separate combinations -- and then watched as the opposing species grew toward the empty space in the middle. Typically the fungi would meet near the center after about 20 days, after which they would begin an "interference competition" in which each species sought to overtake the other and claim available space.

Often the competitions would end in a stalemate. But in many cases the stronger species would overtake the other, growing on top of and then decomposing the weaker species.

The researchers then ranked the competing species based on a variety of traits -- including how fast they grew, the density of their biomass, and the types of enzymes they produced (which presumably were used to eliminate each other). They noticed that those species that grew fast, developed greater density, and produced more varied enzymes were most successful overall.

Once they ranked the species in terms of their relative strengths and competitive traits, they modeled how they would compete within a larger community comprised of many different interacting species.

They then ran those results through a simulation model that predicted how the different species would perform within larger, more diverse communities -- including, for example, landscapes including three, five, 10 and more additional fungi species.

According to their results, common traits emerged among species that were able to dominate single competitors -- just as strong gladiators all presumably shared similar competitive strategies and traits. But when additional species were added to the community, those competitive advantages meant less, allowing even the weakest species to maintain a foothold.

https://nioo.knaw.nl/en/news/diversity-begets-diversity-competition-space