Photo credit: MacJewell/Creative Commons
The Tawny Owl population in Finland is changing colors from gray to brown. The gray owl used to have a better chance of surviving in the winter snow, but now due to climate change the playing field has shifted in favor of the brown owl.
The geography and climate of the earth has without a doubt changed drastically over its long life span; so unsurprisingly the species that inhabit it have changed too. Every species naturally has individuals of a population who are more likely to survive and reproduce in their environment. Overtime as these “more fit” individuals have more and more offspring, they become more prevalent in the population. This process is known as microevolution and it is how species are able to adapt to new environments. It is assumed that global climate change, due to global warming, will cause an increase in microevolution in species. But these millions of years of adaptations can also be the downfall for some species in the face of climate change if they cant adapt quick enough. Species are obviously changing continuously, however it is a difficult task to scientifically prove that microevolution is occurring as a result of recent climate change since there are many factors that contribute it. Despite the difficulty, Patrik Karell from the University of Helsinki has done it. Karell and his team at the university of Helsinki, studied the feather colors of a population of tawny owl in Finland and proved that climate change is causing a change in feather color. But how exactly can this relationship be proved?
The tawny owl population in Finland is an ideal candidate for a study on microevolution. It has long been known that the gray tawny owl has a survival advantage over the brown tawny owl and it has therefore existed in a larger proportion. The gray owl blends into the snow in the winter, which is advantageous because it enables it to hide from predators. The tawny Owl population is also an ideal candidate for a study on microevolution because the trait that is favored, the feather color, is determined by genetics. Karell’s study, published in Nature Journal, proved there are two alleles, or sections of DNA, brown and gray, that determine the feather color. The brown allele is dominant, meaning it will beat the recessive gray allele in the competition for which color an owl is born.
Once the study determined the genetic basis for the adaptive trait, feather color, the study modeled the survival of the gray tawny owl verses the brown tawny owl. The study compiled information on the tawny owl population in Finland to model the survival of the different colored owls in relation to the climate. The study used data collected by amateur bird ringers from the Finnish Museum of Natural History, who used a capture-mark-recapture method. The capture-mark-recapture method used to collect the data involves capturing an owl from the wild, recording its feather color and tagging it, then releasing it back into the wild. Owls are then recaptured and using a specific formula based on the number of tagged owls captured, the population of brown and gray owls is estimated. They tracked the number of each color over time with relation to the climate for a total of 28 years. This data became a great resource for this study on microevolution.
Karell and his team compiled the data and examined trends in the color of tawny Owls. The results demonstrated that brown individuals have a lower survival rate in deeper snow. Brown owls stand out in the snow and are consequently susceptible to predators. Over the years of the study, the averages of snow decreased as a result of warming average temperatures. As the snow decreased, the number of gray owls remained constant but the number of brown owls increased. The environment no longer fights against the survival of the brown owl so its numbers have increased. The brown owl can blend into the environment in the absence of heavy snow, which helps it survive. The data used in the study is summarized in the graphs below.
The shift in the frequency of brown owls is significant and is greatly impacting the appearance of the tawny owl population in Finland. Gray owls and brown owls now exist at equal rates. So far the tawny owl has been lucky, their change in apperance has presented no threat to their survival. However this could mean trouble down the road for the tawny owl. Without its adaptive advantage, there will be a decline in the number of gray owls in the population of tawny owls. Since the brown feather color is dominate over the gray feather color they will soon outnumber gray owls. A loss of gray owls would mean a loss of genetic diversity. High genetic diversity is key to longterm survival of a species. Think about it this way, the more colors and types of shoes that are in your closet, the higher the diversity and the higher the chance you will find the perfect pair for an outfit. With only a few pairs, the chances of matching are slim. For animals this means trouble, without enough shoes, genes, they will not be able to adapt and survive in changing environments. As a society we must think about how our actions affect the species, like the tawny owl, who live on our planet, and practice eco-friendly behaviors for a healthier planet!
Reference: Karell, Patrik, Kari Ahola, Teuvo Karstinen, Jari Valkama, and Jon E. Brommer. "Climate Change Drives Microevolution in a Wild Bird." Nature Communications 2. 2011/02/22 (2011). Nature. Web. 01 Mar. 2011.
View the original article here: http://www.nature.com/ncomms/journal/v2/n2/full/ncomms1213.html
Check out a news article on the change in the tawny owl feather color: http://news.bbc.co.uk/earth/hi/earth_news/newsid_9401000/9401733.stm
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