Evolution of Canadian Red Squirrels Due to Climate Change

         Both evolution and global warming are happening, have been happening, and will continue happening.  The realities of these two processes cannot be disputed.  Throughout history, Earth has undergone periods of warming and cooling.  However, this most recent global warming carries heavy implications for life on Earth.  Effects of global warming include rising sea levels (about 17 cm in the last century due to melting glaciers¹), warming oceans (0.302 °F increase since 1969²), rising global temperatures (peak summer and winter temperatures are getting warmer³), and shifting onset of seasons (the hottest and coldest days of the year occur almost 2 days earlier than 50 years ago⁴).  In the last century, average global temperatures have risen more rapidly than in the last 1,300 years⁵, and this accelerated warming is believed to be caused by human activity (anthropogenic).  The current warming trend is due to increased concentrations of green-house gases, such as carbon dioxide, methane and nitrous oxide, trapped in the atmosphere.  Man's burning of fossils fuels, primarily coal and natural gas, to produce electricity emits the most green-house gases.  This global warming is different because of humans.  Change is literally in the air, and organisms must adapt.  Those that adapt quickly have a greater probability of survival. 

Because the change to climates and environments is not small, global warming has become an evolutionary force.  For example, the Canadian red squirrel breeds earlier than it did 10 years ago due to factors including warmer spring temperatures and increased food availability⁶.  A study by McGill University and the University of Alberta on a population of red squirrels in Kluane Lake, Yukon, Canada, found the parturition date, when the females begin spring breeding, for females born in 1998 was 18 days earlier than the mean lifetime parturition date for females in 1989 (moved up 6 days per generation)⁷. The offspring of female squirrels who breed earlier have a selective advantage because they are larger and can store more pinecones than their peers by the fall⁸.  Therefore the older offspring are better equipped for surviving winter, reproducing, and passing on the genes for earlier breeding⁹.  Earlier breeding has a heritable genetic basis, yet it is worth noting that phenotypic plasticity also played a role for each generation¹⁰.  Earlier breeding was partly a response to the number of pinecones available over a female’s lifetime increasing by more than 35% over the 10 year period¹¹.  The Canadian red squirrel has undergone directional selection because human activities have altered the environment in which it lives. 

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^1,2,5 http://climate.nasa.gov/evidence

^3,4 http://www.livescience.com/5296-timing-seasons-changing.html
 

^6,7,10,11 Réale, D., A. G. McAdam, S. Boutin, and D. Berteaux. 2003. Genetic and Plastic Responses of a Northern Mammal to Climate Change. Proceedings of The Royal Society of London Series B-Biological Sciences 270:591-596.

^8,9 http://evolution.berkeley.edu/evolibrary/news/060701_warming

Welcome!

Hello and welcome to one of Rice University's Evolution class blogs. We are Group One. Each member of our group will write posts relating to a topic of evolution with a special focus on case studies of evolution resulting from increasing pollution. We hope you find our blog to be informative and enjoyable!

- Group One (Daniela Garza, Carolina Osuna, Stella Keck, Jessica Lee, Soongjin Ahn, Christina Dana, Ryan Johnson, and Mary Morales)