When scientists attempt to understand how climate change
might reshape our environment, they must grapple with the seemingly endless
complexity of interacting systems.
For those considering the likely fate of particular species,
there is now a relatively simple rule of thumb to help calculate the likely
effect of climate change where species interact.
"A lot of the discussion about climate change focuses
on the fate of individual, iconic species, but to evaluate the effects of
future environmental changes we need to account for interactions between
species," James Cook University evolutionary ecologist Tobin Northfield
"We need to consider how species co-evolve how they are
adapting in response to each other, as well as in response to climate change.
In addition, as difficult as it may seem, we need to account for changing
interactions, as the species evolve."
Research published this week in PLOS Biology argues that
where species have conflicting interests (for example where one species becomes
very aggressive towards the species it competes with for food) their coevolving
relationship is likely to reduce the effects of climate change on both species.
Where species interact in a non-conflicting way (for example
where one species simply avoids the other species it competes with for food,
rather than becoming aggressive) the effects of climate change are likely to be
Dr Northfield, now at James Cook University in Cairns,
worked at the University of Wisconsin with Dr Anthony Ives to develop a rule of
thumb to help scientists calculate how co-evolving species might change over
"When evaluating the effects of climate change, there
is already so much to consider, we were hoping to find some simple
answers," Dr Northfield said.
Drs Northfield and Ives have developed modelling tools and
guidelines to help scientists extrapolate from the short to longer term.
"Many earlier studies have looked at how climate change
might affect the evolution of particular species, and more recently there has
been some investigation of how interacting species might change in the short
"We used simple models of competition, predation and
mutualism to consider how these interactions might change over longer time
periods, and how that, in turn will affect each species," Dr Northfield
"The nature of climate change means that we don't have
years and centuries to observe changes in nature. Mathematical modelling gives
us a way to calculate what the future might look like," he said.
The study began, with funding from the United States
Department of Agriculture, as an investigation of how pest insect population
densities might change in cropping regions.
"One of our findings is that when predators attack crop
pests and benefit agriculture, such as lady beetles eating aphids, the predator
and prey will both evolve in response to climate change and will reduce the
effect of climate change on crop damage," Dr Northfield said.
The researchers have suggested ways to evaluate their rule
"Insect populations are a good testing ground for our
theory, because it is relatively easy to include many insects in an experiment,
and they reproduce quickly, allowing faster evolution," Dr Northfield
"For example, by looking at insect/plant interactions
at different latitudes, it is possible to observe how coevolving species, and
their interactions, vary in different climatic conditions.
"If you know what type of coevolution drives the
interaction, you can make predictions of how it will affect the species
densities across the different latitudes."
The paper also suggests ways for researchers to determine
which type of coevolution (conflicting or non-conflicting) drives a particular
"This is not as clear and straightforward as you might
think," Dr Northfield said. "In some plant-insect relationships, for
example, some insects that pollinate flowers can also evolve to steal from the
flower without providing the flower with the benefits. Of course, this
conflicts with what is best for the plant. So we've also developed some
guidelines for classifying species interactions."