Firstly, what do you consider a different species? I would like to think a different species is one who cannot reproduce with another. If that is in fact the case I have an observed example for you.
Speciation in action among Larus seagulls.
Gulls of the genus Larus form an evolutionary ring around the North Pole, which acts as a geographic barrier for their population. Although some have argued that this is technically not an example of a ring species(Liebers et al., 2004), it is certainly an example of speciation in action.
In the image above, one can see the "ring" the sub-species of gulls make around the pole. The herring gull can interbreed with its neighbor, the American herring gull, which can interbreed with its neighbor, the Vega gull, which can interbreed with its neighbor, Birula's gull, which can interbreed with its neighbor, Heruglin's gull, which can interbreed with its neighbor, the Siberian black-backed gull, which can finally interbreed with its neighbor, the lesser black-backed gull. (Image Source 4)
However, the populations of the herring gulls and the lesser black-backed gulls are genetically different enough so that, even though they now live in relatively the same area, they cannot reproduce together. Thus, they can not truly be the same species. As you move west around the pole, the genetic difference in each population becomes slightly greater and greater until the two ends meet, at which we have two separate species.
Examples such as the Larus gulls essentially show all the steps of speciation laid out in a ring. Each population is slightly different from the last, until the two ends meet and these populations are completely different species that will now continue to grow more and more genetically different. To the left you can see the two distinct species of gulls, the herring gull and the lesser black-backed gull. (Image Source 5)
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