What Is Allopatric Speciation?

The work of Alfred Russel Wallace and the observations of Charles Darwin (while aboard his journey on the HMS Beagle) gave light to the current science of biogeography. This led to the current assumptions that species have a definite area of origin, achieve a broader region of distribution, and then become modified or produce descendent species in other regions (Laughlin 2015). This again relates to Wallace’s observation that species reproduce rapidly and without being checked will rapidly expand into any available land and fill it to its capacity. This rapid reproduction and expansion enable such processes as sympatric and allopatric speciation. Allopatric speciation is a direct result of geography, where a physical barrier divides a population,

The idea first came to him when he realized that some of the continents looked like puzzle pieces which could fit together, but he dismissed the idea as it seemed improbable. Within the next few years, more and more scientists were beginning to discuss the idea that there must have once been a land bridge between the continents to explain the similarity of organisms on the various continents. It was far too improbable that identical species had appeared separately on multiple different continents. They must have somehow originated in the same place before becoming separated. With that in mind, they realized that the species were not identical on various continents, but each continent seemed to contain the same families and genera. It would then make sense through evolution that the current genera are the species of the past which have only further diverged upon isolation creating a multitude of new species. There were multiple problems with the hypothesis of interconnecting land bridges, however. One of which is that if the land bridges are no longer visible today, they must have sunk into the oceans, which would have caused the ocean levels to rise drastically and put parts of multiple continents under water. One hypothesis is that this would have caused the water levels to have risen high enough to cover

The South American and African coasts were one example, and they could have formed one large land mass which split during the Cretaceous period. North America and Europe could have formed another large land mass which then began to split apart during the Tertiary period. India, Australia, and Antarctica formed what may have been the largest land mass against one of South America’s coasts and began to split apart during the Jurassic period. Each subcontinent then split apart further and the pieces drifted apart on their own. It is possible to determine roughly the era that the continents must have separated by closely analyzing the biogeography of each continent. The mountain ranges along each continent could be explained by the drag of the continents and by tectonic forces. The combined effects of plate tectonics, continental drift, and the formation of barriers led to the current biogeography observed across the globe. The theory of continental drift solved the problems of each of the hypotheses of permanence and land bridges, while maintaining the benefits of both. Continental drift takes into account that the continents were at one time connected as the land bridge hypothesis did, but it solved the problem of sinking land bridges. Instead of having intermediate continents, it