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Understanding mutualism can help control the spread of invasive species

Understanding mutualism can help control the spread of invasive species
Degree of dependence leading to fastest range expansion of P for different benefits of mutualism (α, β) provided by P and F. Each gridcell in the heatmap shows the degree of dependence that leads to fastest range expansion of species P for pairs of parameters (α and β). (a) value of DP leading to fastest spread of P (b) value of DF leading to fastest spread of P, (c) value of (DP − DF). If (DP − DF) > 0 (blue regions), it implies that species P depends more on species F than F’s dependence on P. The reverse holds true when (DP − DF) < 0 (red regions). Parameter values (rP = 0.3, rF = 0.3, βPF = βFP = 0.25). Credit: Ecology (2023). DOI: 10.1002/ecy.4171

Cooperation between species to help each other's survival is known as mutualism. It is seen among many types of organisms, such as plants and fungi that exchange nutrients with one another, plants that provide bees with nectar in exchange for pollination, and sea anemones that provide protection for clown-fish in exchange for excreted nutrients.

Recently, scientists have found evidence that some become even more invasive in the presence of helpful partners, as can happen with certain and fungi or fig trees and wasps. But other studies have suggested that that didn't rely on mutualist partners were more invasive.

Recent research at the University of Minnesota, published in the journal Ecology, attempted to identify the conditions under which a mutualistic partner could make a species more or less invasive. To study this, they built mathematical models called integro-difference equations (IDEs).

IDEs take into account the effects of mutualism on growth and dispersal of species and are useful tools to model spatial processes. Mathematical models are helpful in understanding like invasion that occur over many years and can be difficult to study in the field.

The team modeled a phenomenon called mutualism dependence, which measures how much a species depends on benefits from its partner for growth. Highly dependent species are often called "obligate mutualists" and lower dependent species are called "facultative mutualists." They then tried to understand how the invasive ability of a species varied as a function of its dependence on its partner.

The research found that:

  • Based on how much nutrition (or other benefits) a partner provides, being more or less dependent on a partner could increase a species' invasiveness, as measured by its range expansion speed.
  • Having too many partners could stop a species' invasion, as there is a large cost associated with supporting them.
  • Mutualistic dependency modifies a species' spatial distribution, impacting whether it is more populous at the edges or center of its range.
  • As become more widespread, this research could eventually help protect native habitats from mutualistic invaders. Understanding the mutualistic properties of an invasive species could help researchers identify ways to slow the invasion.

"Understanding the role of mutualisms is critical to preventing 'invasional meltdowns' which is a process by which mutualists accelerate each others' invasions in a positive feedback loop," said lead author Naven Narayanan Venkatanarayanan.

"Invasional meltdowns greatly speed up extinction of native species and communities. Future applications of this research include identifying and biologically controlling populations of mutualist partners of the invasive species, such as fungi."

More information: Naven Narayanan et al, Mutualisms impact species' range expansion speeds and spatial distributions, Ecology (2023). DOI: 10.1002/ecy.4171

Journal information: Ecology

Citation: Understanding mutualism can help control the spread of invasive species (2023, October 19) retrieved 22 February 2024 from
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