Which limitation does the biological species concept face?

The biological species concept is defined primarily by the ability of individuals to interbreed and produce viable, fertile offspring. This concept emphasizes reproductive isolation as the key criterion for defining a species. However, it encounters limitations, particularly regarding its applicability to asexual organisms and extinct species represented by fossils.

Asexual organisms, such as bacteria and some plants, reproduce without the need for a mate, so reproductive isolation can't be evaluated based on interbreeding. Consequently, the biological species concept does not provide a clear method for categorizing or understanding species that do not reproduce sexually.

Similarly, for fossil species, there is no direct evidence of reproductive capabilities, making it virtually impossible to assess whether these organisms would interbreed or how they might have interacted reproductively in their environments. Thus, the inability to apply the concept to these groups highlights a significant limitation in using the biological species concept as a definitive measure of what constitutes a species.