Tectonic Events and Evolution

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Europe is one of the regions that enjoy the diversity of wildlife. Crows are some of the species that are found in Europe and which have been subject to speciation. Two species of the crows known to have originated from the same genus are the Inky-black carrion crow (Corvus corone) found in Western Europe and the Grey-hooded crow (Corvus cornix) found in the eastern part of Europe (Parkin et al., 2003). The two species overlap in a very narrow zone running along the River Elbe in Germany, where at times, they mate with each other to produce fertile hybrids. However, this is a strange result since many species hybrids are often infertile. According to genomic analysis, the two species are actually almost indistinguishable from a genetic standpoint. The only genetic difference between the two species is found in the gene responsible for coloration. The two species are undergoing speciation, which is the slow process of evolving into a distinct species through evolution (Vijay et al., 2016). The speciation of the carrion crows and the hooded crows has taken a different path to that of the Finches. Instead of coming together to create a new species, they are slowly splitting, considering that the crows started from a single European species.

According to scientists, the process of speciation in the two crow species began during the last glacial period from around 115,000 to 11,700 years ago. During this time, there were alternating periods of glacial advancement and retreat, which likely forced the population of the crows to separate. By the time they came back together, the world had warmed up again, and some of them had already mutated. The eastern population had undergone mutation in which they endowed a lighter colored, grey plumage. Instead of mixing, the two species separated with one settling in western Europe while the other in Eastern Europe (Knief et al., 2019). If the geological change was reversed – that is, the glaciation never occurred, there could be only one species of crows in the region. The natural selection and mutation would add new alleles to the crows in a uniform manner, and this means that there could be no variation with the species. Little gene mutations could arise, but it could be evenly distributed with in the populations. As a result, the crow populations would have no variations; there could not have a lighter colored species.

References

Knief, U., Bossu, C. M., Saino, N., Hansson, B., Poelstra, J., Vijay, N., … & Wolf, J. B. (2019). Epistatic mutations under divergent selection govern phenotypic variation in the crow hybrid zone. Nature ecology & evolution, 3(4), 570-576.

Parkin, D. T., Collinson, M., Helbig, A. J., Knox, A. G., & Sangster, G. (2003). The taxonomic status of Carrion and Hooded Crows. British Birds, 96(6), 274-290.

Vijay, N., Bossu, C. M., Poelstra, J. W., Weissensteiner, M. H., Suh, A., Kryukov, A. P., & Wolf, J. B. (2016). Evolution of heterogeneous genome differentiation across multiple contact zones in a crow species complex. Nature communications, 7(1), 1-10.