Relict Populations: Ecologists’ Crystal Ball?

Woolbright et. al. recently published a review piece proposing an interesting idea: using ancient leftover populations and communities to predict the future in the face of climate change. The communities they propose to use are called relict populations, since they are left behind when the ranges of important species in the landscape shift. Such shifts often occur due to climatic change. Figure 1 from the paper is reproduced below as it gives an excellent summary of the phenomenon of relict populations:

Relict populations are at first glance an interesting study in ancient community compositions, fossils of once common populations. However, applying the idea of natural laboratories to them makes more sense, in this framework, than simply using them as history books. Natural laboratories are a useful model for thinking about how to collect data to answer really large scale questions for which experiments might be impractical. I worked with a Bradley University grad student, Al Faulkner, a couple of years ago, on an ongoing ecological natural experiment taking place in Sand Ridge State Forest in Illinois. In this case, an invasion of garlic mustard in the forest was ultimately ecologically interesting because of the weedy nature of that plant (Alliaria petiolata) and its interactions with Robinia pseudoacacia. This experiment would be impossible to reproduce if it were not happening naturally due to the specialized conditions of the forest and the populations within. In the case of climate relicts, they represent a natural laboratory or experiment in evolution because of the time scale they cover. Yet they are often used simply to reconstruct former landscapes

Thinking about them solely as records of the flora from before climate change ignores that they have been evolving for the same amount of time as the surrounding communities since the fragmentation from the larger population. So it is important to remember the other things that can influence the adaptation of a species and community. Genetic drift, adaptation, interaction with other species; these are the other parts of the equation that come into play once climate and geography have conspired to create vestigial populations such as these. Adaptation to the new environment and interaction with new species from a recently changed landscape be separated quantitatively from genetic drift and from each other given careful experimentation, argue the authors, using genetic data. A better understanding of all three, and of the specific ways in which climate and geography intermingle to produce these communities in the first place, gives us a clearer picture of what happened in the past, of how the surrounding flora came to be. As populations get older and they become more separated from each other, they become less homogenous with respect to other populations, and this difference has the capacity to tell us about the interactions between relict and surroundings. Of interest to Woolbright et. al., it also allows us to predict more accurately what will arrive in the future as new changes come to the climate in a global sense. Clearly relict populations are interesting things.

            Iowa, on the other hand, is full of corn.

This is a tried and true complaint from generations of Grinnell students bemoaning their sudden monotony of landscape. And it’s true, Iowa is full of corn, but that doesn’t mean that it’s void of interesting places. In northeast Iowa, hundreds of slopes called algific talus slopes are home to a forest community left over from when boreal forest covered Iowa (Nekola). These slopes retain ancient vegetation from a time when Iowa was colder than it is today. This is due to the cold air that comes up through vents on the ground of these slopes, having passed through ice filled caves left by glacial activity. The resulting community includes northern species such as Abies balsamea (Balsam Fir), which has a range including Minnesota and Canada. These kinds of studies, looking at genetic variation in and between relict populations of balsam fir have already started to be done (Shea and Furnier). Iowa has very unique habitats supporting these types of populations which will be of great interest to those trying to reconstruct the past and those trying to predict the future.

References

Nekola, J. C. (1999). Paleorefugia and neorefugia: The influence of colonization history on community pattern and process. Ecology,80(8), 2459.

Shea, K. L., & Furnier, G. R. (2002). GENETIC VARIATION AND POPULATION STRUCTURE IN CENTRAL AND ISOLATED POPULATIONS OF BALSAM FIR, ABIES BALSAMEA (PINACEAE). American Journal Of Botany, 89(5), 783.

Woolbright S, Whitham T, Gehring C, Allan G, Bailey J. Climate relicts and their associated communities as natural ecology and evolution laboratories. Trends In Ecology & Evolution. July 2014;29(7):406-416.