Genes in place: New research shows location matters for evolution

October 19, 2011

(PhysOrg.com) -- A new paper by researchers at the New England Complex Systems Institute reveals the limitations of evolutionary studies that ignore geography. They show that how individuals are arranged in space, and the patterns formed by living populations themselves, play a crucial role in evolution.

Most mathematical models of evolution consider only the population's overall , essentially assuming that both the and the organisms could be anywhere and that every individual interacts equally with every other--that the is well-mixed. It turns out that the difference between such random mixing and actual is important.

When scientists assume that populations are well-mixed, they miss what happens when offspring live in the spaces left by their parents. For instance, if predators consume all the prey in a given area too quickly, they or their may end up starving later--even though there may be more outside their hunting area. Likewise, a disease that is too virulent may destroy its hosts before getting a chance to spread. In other words, behaviors that appear effective in the short term may lead to their own demise in the long term. When space is ignored, voracious predators and virulent diseases escape from the local effects of their behavior. Those are very different outcomes.

"The same issues arise for all kinds of exploitation. Overexploiting locally impacts your if they live where you did, but not if they can go anywhere they want," NECSI President Yaneer Bar-Yam said. "If you imagine what types of organisms would populate the world if the mixing models were accurate, and what types would exist with spatial distributions, they are completely different."

Even models that allow for space but don't consider all the possibilities it implies, including so called "patch" models, miss the point. "Organisms are 'ecosystem engineers,'" says Blake Stacey, the lead author. "Their actions can change their environment, so models of selection need to include the consequences of an organism's actions on their environment and its effect on later generations," which often matter in the real world.

NECSI researchers have developed an ingenious and intuitive test to determine just how much the spatial arrangement really matters. In the test, organism locations are periodically swapped in a controlled fashion as the evolutionary simulation is run. If the traditional treatments were valid, the swapping wouldn't change the outcomes. But when space is modeled realistically, the swapping dramatically affects evolutionary behavior. What's more, the test can pinpoint where older attempts to include space in the evolutionary equations don't measure up.

These results have implications for how we understand invasive species and emergent pandemics. Human travel often brings species to new areas, sometimes unintentionally, endangering the native organisms. Travel not only transmits diseases but also makes killer epidemics more likely. Furthermore, a spatial understanding of evolution is important for studying the emergence of social behaviors like cooperation and altruism.

The stakes of getting spatial models right extend beyond evolutionary biology. "These concerns are very general," Bar-Yam said. "The same issues arise in social systems, when people exploit their environment. There is a real difference if they suffer the consequences or not. Imagine what would happen if people's homes were swapped around from one house to another every so often. How many people would put time and effort into taking good care of their homes?" With global mobility and connectivity these issues are central to how we take care of our world for ourselves and our children.

Explore further: Predators and parasites may increase evolutionary stability

More information: To download the manuscript, visit: arxiv.org/abs/1110.3845

Related Stories

Predators and parasites may increase evolutionary stability

October 26, 2007

A new study explores the role of natural enemies, such as predators and parasites, for mixed mating, a reproductive strategy in which hermaphroditic plants and animals reproduce through both self- and cross-fertilization. ...

Predators do more than kill prey

January 17, 2008

The direct effect predators have on their prey is to kill them. The evolutionary changes that can result from this direct effect include prey that are younger at maturity and that produce more offspring.

Researchers Find Key 'Conductor' of Nature's Synchronicity

July 22, 2009

(PhysOrg.com) -- Synchronicity in nature is seen in beating hearts, the flashing of fireflies' lights, the ebb and flow of infectious disease—and the simultaneous rise and fall of populations across vast reaches of space. ...

Complexity not so costly after all, analysis shows

September 27, 2010

The more complex a plant or animal, the more difficulty it should have adapting to changes in the environment. That's been a maxim of evolutionary theory since biologist Ronald Fisher put forth the idea in 1930.

Recommended for you

Genomes uncover life's early history

August 24, 2015

A University of Manchester scientist is part of a team which has carried out one of the biggest ever analyses of genomes on life of all forms.

Rare nautilus sighted for the first time in three decades

August 25, 2015

In early August, biologist Peter Ward returned from the South Pacific with news that he encountered an old friend, one he hadn't seen in over three decades. The University of Washington professor had seen what he considers ...

Why a mutant rice called Big Grain1 yields such big grains

August 24, 2015

(Phys.org)—Rice is one of the most important staple crops grown by humans—very possibly the most important in history. With 4.3 billion inhabitants, Asia is home to 60 percent of the world's population, so it's unsurprising ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.