Two species concepts are often used by taxonomists: the biological species concept and the morphological species concept. A third concept, the ecological species concept, defines a species as a group of organisms that occupy the same ecological niche.
Consider the following two scenarios:
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Scenario A: Two populations of a flowering plant, Petalostemon alatus and Petalostemon frondosus, have distinctly different leaf shapes (entire vs. deeply lobed) and flower shapes (tubular vs. bell-shaped). When artificially cross-pollinated, they produce viable seeds that grow into fertile hybrid plants that can interbreed with both parent populations.
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Scenario B: Two populations of a marine polychaete worm, Nereis pelagica and Nereis longicirrata, are morphologically indistinguishable under the microscope. In the wild, they occupy different tidal zones and have different breeding seasons; no natural hybrids are observed. In the laboratory, forced fertilisation produces larvae that do not develop past the trochophore stage.
Using these scenarios, compare the biological, morphological, and ecological species concepts, explaining how each concept would classify the populations in Scenario A and Scenario B, and discuss the advantages and limitations of each concept.