Michael Dillon (left), an associate professor in the University of Wyoming Department
of Zoology and Physiology, and Arthur Woods (right), a professor of biological sciences
at the University of Montana, were part of a research group that examined how animals’
ability to respond to climate change likely depends on how well they modify their
habitats, such as nests and burrows. Here, Dillon bends over to examine a plant and
measure microclimates at the UW-National Park Service Research Station in Grand Teton
National Park. Their work, titled “Extended Phenotypes: Buffers or Amplifiers of Climate
Change?,” was published in the June 16 issue of Trends in Ecology and Evolution. (Sylvain
Pincebourde Photo)
Birds build nests to keep eggs and baby nestlings warm during cool weather, but also
make adjustments in nest insulation in such a way the little ones can keep cool in
very hot conditions. Mammals, such as rabbits or groundhogs, sleep or hibernate in
underground burrows that provide stable, moderate temperatures and avoid above-ground
conditions that often are far more extreme outside the burrow.
Michael Dillon, an associate professor in the University of Wyoming Department of
Zoology and Physiology, was part of a research group that examined how animals’ ability
to respond to climate change likely depends on how well they modify their habitats,
such as nests and burrows.
So, how are these animals doing? Are they succeeding, struggling, or are their efforts
a mixed bag in adapting their habitats to climate change?
“One of the key reasons that we wrote this paper is that we don’t know the answer
to this very important question!,” Dillon says. “We hope the paper will encourage
scientists to begin answering this question.”
Dillon is a co-author of a paper, titled “Extended Phenotypes: Buffers or Amplifiers of Climate Change?,” that was published June 16 in Trends in Ecology & Evolution. The journal publishes commissioned, peer-reviewed articles in all areas of ecology
and evolutionary science.
The lead author of the paper is Arthur Woods, a professor of biological sciences at
the University of Montana. Other contributors to the paper were from the University
of Tours in Tours, France; and Stellenbosch University in Stellenbosch, South Africa.
The study investigated extended phenotypes, which are modifications that organisms
-- birds, insects and mammals -- make to their habitats.
“An extended phenotype can range from simply a hole in the ground occupied by an animal
to leaves rolled into cavities by insects, to nests of all shapes and sizes built
by birds and mammals, to termite mounds and bee colonies,” Dillon says.
Extended phenotypes are important because they filter climate into local sets of conditions
immediately around the organism. This is what biologists call the microclimate.
Because extended phenotypes are constructed structures, they often are modified in
response to local climate variation and, potentially, in response to climate change.
This process is called plasticity of the extended phenotype.
“One example might be a bird nest that is well insulated to protect eggs or young
birds from cold. As climates warm, if the bird does not adjust insulation in the nest,
it may, in fact, cause the young to overheat,” Dillon explains.
In another prime example, termites build mounds that capture wind and solar energy
to drive airflow through the colony, which stabilizes temperature, relative humidity
and oxygen levels experienced by the colony.
However, the idea of microclimates is broader than constructed habitats. Microclimates
typically differ substantially from nearby climates, which means that the climate
in an area may provide little information about what animals experience in their microhabitats.
As an analogy, although a weather station might tell the public that the temperature
in Laramie is 90 degrees Fahrenheit, simply by moving from the south to the north
side of a building, one can experience microclimates that are strikingly different
and often not captured by the weather data, Dillon says.
The same is true of animals of many different sizes. For example, a moose can move
from an open sagebrush landscape to a shaded river corridor to cool off; a snake can
move from its underground hole to a sunny rock to warm up; and a tiny insect shuttling
between the top and bottom of a leaf can experience temperature differences of more
than 20 degrees Fahrenheit.
“So, animals use microclimates, both by simply moving but also by building structures,
such as nests, burrows, mounds and mines,” Dillon says.
Across the globe, rising levels of carbon dioxide in the Earth’s atmosphere are causing
temperatures to rise and precipitation patterns to shift. For biologists, a key problem
is to understand current effects of climate change on species, and to predict future
effects, including how species’ ranges may shift and what the relative risks of extinction
are for different animal species’ groups.
The research team favors a renewed effort to understand how extended phenotypes mediate
how organisms experience climate change.
“We need a much better understanding of the basic biophysical principles by which
extended phenotypes alter local conditions,” says Sylvain Pincebourde, an ecologist
in the Insect Biology Research Institute at the University of Tours and one of the
paper’s co-authors.
Another key challenge is to understand how much plasticity there is in extended phenotypes,
and how much and how rapidly they can evolve.
“At this point, we pretty much have no idea,” Dillon says. “Can structures that buffer
temperature variability keep up with the pace of climate change?”
