Summary
New research reveals that evolution in animals in response to humans may be happening faster than imagined. In particular, some species are being observed as adapting to living by roads. Roads apply selection pressure, but they also split up populations. The decreased gene flow could be causing an increased rate of evolution. In southwestern Nevada, it appears that cliff swallows have been adapting to roads. Cliff swallows naturally build their nests on cliffs, but they also nest heavily under road bridges and overpasses. Charles Brown of the University of Tulsa has collected cliff swallow road kill for the past 31 years. Over time less road kill appeared. The road kill that appeared also had longer wing spans than other birds, and the average wing span of cliff swallows has decreased since 1982. This suggests that in a short period of time, cliff swallows have adapted to evade oncoming cars by having shorter, more maneuverable, wings. Spotted salamanders are also adapting to roads. They hatch in vernal pools, and ones near roads are exposed to many contaminants such as salt. Eggs normally near roads that were transplanted deeper into the forest survived equally well as the eggs normally in the forest. However, eggs transplanted from deeper in the forest to the roadside had a much lower survival rate.
Relevance
The evolution of cliff swallows and spotted salamanders directly relates to the ecology unit. In our ecology unit, we discussed the interactions between species. Specifically we learned about the impact of humans on other species. Humans cause fragmentation, or the division of populations of species by roads, pollution, and much more. We have also discussed the evolution of species in reaction to environmental changes. This article connects these ideas because the swallows and salamanders evolved in direct relationship to human impacts, and our fragmentation has sped this process up. It also helps to answer the question of the long term impacts of humans on the environment. Species may be adapting quickly enough to keep up with the extreme changes people impose.
Cossins, Dan. "Evolution Takes a Road Trip." The Scientist. 1 June 2013. Web. 20 October 2013. <http://www.the-scientist.com/?articles.view/articleNo/35671/title/Evolution-Takes-a-Road-Trip/>
What would happen if the human, in which the animals depend on, are removed (for instance, it becomes a protected site)?
ReplyDeleteAlthough I could not find specific predictions for the outcomes of these occurrences, based on what I know about evolution, they would most likely adapt to the new area without humans or be killed if they were extremely dependent on humans. Specifically in this article, the eggs of the salamanders adapted to roadside pollution survived without the added pollution. The shorter wingspans of swallows may or may not be an issue without the presence of cars.
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ReplyDelete(Sorry, I accidentally pressed the "Delete" button on my comment above.)
ReplyDeleteIn what other urban or suburban places are species being observed as adapting to life alongside humans?
How short could the wings of the swallows get before the wings would not be able to support the swallow, and would the swallows body get smaller in order for the ratio of body mass to wingspan be equal?
ReplyDeleteThis is actually a very complex question (which is why I didn't answer it). Here is an excerpt from "Movement and Locomotion in Animals" by A. Kumar. "Rayner studied the sizes and shapes of bird wings... He started with measurements of body mass, wing area, and wing span... these measurements are related to each other (heavier birds have generally larger wings), but the relationships are not simple. If birds were geometrically similar to each other, wing areas, would be proportional to the squares of the bird's lengths, and masses to the cubes of the length implying that wing areas would be proportional to the two-thirds power of body mass--- four times the area for eight times the mass." But wing shape varies allowing different ratios. " Most birds that fly long distances have wings of high aspect ratio, and with tapered or elliptical wingtips. This is particularly noticeable on soaring birds such as albatrosses and eagles. By contrast, hawks of the genus Accipiter such as the Eurasian Sparrowhawk have wings of low aspect ratio (and long tails) for maneuverability." What I am saying is I am not sure at what point the ratio becomes too small because both ratio and wing shape factor in, but I am presenting the information I found in case it helps.
DeleteIn response to Hannah Yin, there are many places where species are adapting to life alongside humans. For example, humans introduced the rat poison resistant Algerian mouse to other common species of mice, creating hybrids that are immune to the poison Warfarin. Bedbugs have also become resistant to efforts to eradicate them. One adaptation is a thicker exoskeleton that resists pesticides. One familiar example, although not recent, is the peppered moths. These moths evolved to be darker in industrialized areas of Britain where soot had killed the light colored lichen.
ReplyDeleteHere are the links to related articles (the second contains more examples of adaptations):
ReplyDeletehttp://animals.about.com/cs/evolution/a/aa090901a.htm
http://www.popsci.com/science/article/2011-09/ten-new-or-newly-discovered-animal-evolutions-including-humans