Evolution in action
April 24, 2012 at 10:38 am
(This post was last modified: April 24, 2012 at 10:39 am by Phil.)
In this thread let's ignore all the fossil evidence, DNA (genetic) evidence, homeologic evidence, molecular evidence, all the evidence we can possibly use for evolution and instead focus on the evolution we see all around us. I'll start with two examples that will clearly show evolution and speciation happening right before our eyes.
My first example is the Sockeye Salmon of Lake Washington (east of Seattle Washington). In the 30s and 40s they were first introduced in Lake Washington and fairly quickly they colonized the mouth of the Cedar river. By the mid 50s they had also colonized Pleasure Point beach. By the mid 90s (only 40 years later) these two populations diverged. In the Cedar river where the water flows rapidly, the male Salmon are more slender so they can fight the currents while the females are larger so they can dig deeper holes in the river for their eggs (so the current doesn't take the eggs). The Salmon that live in the warmer, stiller waters of Pleasure Point have males with larger rounder bodies so they can fight of rival males for mating privileges while the females are smaller since they do not have to dig deep holes to protect their eggs. These two distinct populations are genetically isolated and already after only 40 years (as of 1997 to be exact) show differences that would be recognized as distinct species in most organisms. Andrew Hendry of McGill University has shown us that this split (an example of allopatric speciation) has happened in 40 years and within a few generations they will be defined as a separate species.
My second example is a bird quite a few of us are familiar with. It's the common sparrow, specifically the European House Sparrow. The reason I am looking at this bird is because it isn't endemic to North America, or should I say it wasn't. The European House Sparrow was introduced to North America in the summer of 1851 in Brooklyn NY. Since there is only one tree that grows in Brooklyn (it was in a book, look it up), they quickly flew the coop so to speak and spread all over a range from Costa Rica in the south to the boreal forests of Canada in the north. Since we know they all came from one ancestral species and that species was all fairly similar (since the original population was small) and they spread all over North America, we know they are quickly diverging from one another and becoming new species (another example of allopatric speciation). We see the northern Sparrows follow Bergmann's rule (In zoology, Bergmann's rule is an ecogeographic rule that correlates latitude with body mass in animals) and they have larger bodies than those in the south. The reason for this is that larger bodies are needed to conserve heat. The northern Sparrows are darker than their southern relatives. Wing length is different, bill shape and of course length (shades of the Galapagos Finches). Many more difference can be found in the literature and online. The differences between the northern and southern Sparrows tend to be so extreme that bird watchers from the north can't even tell they are looking at the same species as bird watchers in the northern latitudes.
Ok, you have two examples. Let's hear yours.
My first example is the Sockeye Salmon of Lake Washington (east of Seattle Washington). In the 30s and 40s they were first introduced in Lake Washington and fairly quickly they colonized the mouth of the Cedar river. By the mid 50s they had also colonized Pleasure Point beach. By the mid 90s (only 40 years later) these two populations diverged. In the Cedar river where the water flows rapidly, the male Salmon are more slender so they can fight the currents while the females are larger so they can dig deeper holes in the river for their eggs (so the current doesn't take the eggs). The Salmon that live in the warmer, stiller waters of Pleasure Point have males with larger rounder bodies so they can fight of rival males for mating privileges while the females are smaller since they do not have to dig deep holes to protect their eggs. These two distinct populations are genetically isolated and already after only 40 years (as of 1997 to be exact) show differences that would be recognized as distinct species in most organisms. Andrew Hendry of McGill University has shown us that this split (an example of allopatric speciation) has happened in 40 years and within a few generations they will be defined as a separate species.
My second example is a bird quite a few of us are familiar with. It's the common sparrow, specifically the European House Sparrow. The reason I am looking at this bird is because it isn't endemic to North America, or should I say it wasn't. The European House Sparrow was introduced to North America in the summer of 1851 in Brooklyn NY. Since there is only one tree that grows in Brooklyn (it was in a book, look it up), they quickly flew the coop so to speak and spread all over a range from Costa Rica in the south to the boreal forests of Canada in the north. Since we know they all came from one ancestral species and that species was all fairly similar (since the original population was small) and they spread all over North America, we know they are quickly diverging from one another and becoming new species (another example of allopatric speciation). We see the northern Sparrows follow Bergmann's rule (In zoology, Bergmann's rule is an ecogeographic rule that correlates latitude with body mass in animals) and they have larger bodies than those in the south. The reason for this is that larger bodies are needed to conserve heat. The northern Sparrows are darker than their southern relatives. Wing length is different, bill shape and of course length (shades of the Galapagos Finches). Many more difference can be found in the literature and online. The differences between the northern and southern Sparrows tend to be so extreme that bird watchers from the north can't even tell they are looking at the same species as bird watchers in the northern latitudes.
Ok, you have two examples. Let's hear yours.
