According to the evolutionary species concept, what defines a species?

The evolutionary species concept defines a species as a single lineage that maintains its identity from other lineages and develops its own distinct evolutionary path due to specific selection pressures. This concept emphasizes the importance of lineage and evolutionary history, suggesting that species are not merely defined by physical traits or ecological factors, but rather by their unique evolutionary trajectory.

In this context, the focus on a single lineage allows for the inclusion of genetic and evolutionary aspects that contribute to the distinctiveness of a species. Each lineage may respond differently to environmental changes and selective pressures, leading to adaptations that further solidify its identity as a species. This concept is especially applicable in situations where reproductive isolation may not be the only defining characteristic of a species, highlighting the importance of evolutionary processes in species definition.

The other options do not encompass the complexities of evolutionary history and selection pressures in defining a species, thus lacking the comprehensive scope provided by the evolutionary species concept.