The Biological Species Concept (BSC) defines a species as a group of organisms that can interbreed and produce viable, fertile offspring in natural conditions. It emphasizes reproductive isolation from other groups.
An example of the BSC applied to birds can be seen in the case of the eastern and western meadowlarks, which are two species within the genus Sturnella: the Eastern Meadowlark (Sturnella magna) and the Western Meadowlark (Sturnella neglecta).
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Reproductive Isolation: Although these two species have overlapping ranges and have similar physical appearances, they do not interbreed in nature due to differences in their mating calls and behaviors. The eastern meadowlark has a distinct song that attracts mates of its own species, while the western meadowlark has a different song that appeals to its own species.
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Viable Offspring: If individuals from these two species were to mate (which is highly unlikely in natural settings due to their reproductive isolation), any resulting hybrid offspring would likely have reduced fitness and may face difficulties in survival or reproduction; thus, they would not contribute to the gene pool of either species effectively.
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Natural Conditions: The BSC focuses on the fact that these two species maintain their distinctness in the wild, where they have evolved in different ecological contexts and behaviors that reinforce their separation.
Through this example, we can see how the concept helps to clarify the status of meadowlarks as distinct species, illustrating the principle of reproductive isolation central to the Biological Species Concept.