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.
416 words
1,2,5 http://climate.nasa.gov/evidence
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
From reading this post I understand that both increased food availability and warmer temperatures has driven these red squirrels to breed earlier, but which factor is the greater driving force for this? I would think that warmer temperatures would be the most influential factor. Is there any literature that discuss this?
ReplyDeleteI personally believe the warmer temperatures were the greater factor at play here. The analogy that I think of is how flowers bloom earlier now because of changes in the weather (earlier warmer temperatures causing flowers to bloom earlier). So the squirrels are simply reacting to these two environmental cues: a percieved spring time because of the earlier warmer temperatures and a greater food supply. It's hard to say which is the greater factor in influencing parturition date because the warmer climates inevitably also affect the pine trees and the timing pinecones are produced.
ReplyDeletehow does the small change in global warming in a degree or two really make the squirrels breed almost a week earlier per generation? That seems like a drastic amount and I'm wondering the connection
ReplyDeleteIt's not small though to organisms who are temperature-sensitive because they use temperature cues to know when to initiate mating, breeding, etc. The somewhat drastic results of moving parturition date up 6 days/generation for 3 generations was the reason I was actually interested in writing about these squirrels
DeleteThis is interesting because while global warming is normally considered a "bad" thing, in the squirrel's case, it is actually beneficial because it has changed seasonal times. In the long run, the bad things will definitely outweigh the good things that global warming brings. With rising sea levels and changing weather patterns, these same squirrels will be facing a very different environment in coming years.
ReplyDeleteI had similar thoughts - that the effect of global warming seems to be beneficial for the Canadian red squirrels...Could there be any potential negative effects though?
DeleteI don't really look at these results as a beneficial or negative for the squirrels. I was more noting a species behavior change as a result of its environment changing - adaptation and natural selection at work. It's is true that thousands of organisms/ animals on earth will be facing a different environmet in the coming years, so it will be interesting to see the many adaptations that occur.
DeleteI wonder if there are other species that are experiencing this phenomenon and how their role in the ecosystems would change, or if any other species would be harmed/helped by the change in breeding time. For example, if the squirrels ate a certain plant and spread its seeds, would the plant also experience better success from a longer dispersal/growth season? Since ecosystems are so complex, I wonder if this change would affect the survival and adaptation of other species.
ReplyDeleteOf course there are other species experiencing this phenomenon because global warming is affecting the planet as a whole. And because ecosystems are all interconnected, a change in one species will certainly affect another species.
DeleteI had heard about the numerous effects the current global warming has on animals (including altered migration patterns and shifts in an animal’s native range). Do scientists know if these changes in behavior occur before every warming/cooling trend? Or are we mainly observing them now due to the unprecedented warming rate currently occurring?
ReplyDeleteI'm not sure because the study didn't investigate this, but in terms of natural selection, we know that species can only adapt to their current environment (they can't predict the future and adapt). So in my opinion, changes would occur during or after a warmin/cooling trend not before. Additionally, the unprecedented warming rate played a rol in the study, the researchers spoke to this in their paper.
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