Isopygy

Isopygy is a term used in genetics and evolutionary biology to describe the phenomenon where two different species or populations evolve independently but arrive at a similar phenotypic trait or set of traits. This convergence occurs because they face similar environmental pressures or selective forces, leading natural selection to favor comparable solutions. It is a form of convergent evolution, but specifically focuses on the similarity of the resulting phenotype rather than the underlying genetic or developmental pathways.

The term implies that despite divergent evolutionary histories and potentially different genetic mechanisms, the external appearance or functional characteristics of the organisms become remarkably alike. This can lead to difficulties in distinguishing between species based solely on morphology. For instance, if two unrelated species inhabit arid environments, they might both evolve traits like water storage capabilities or reduced leaf surface area to conserve water, even if their common ancestors lived in vastly different conditions. The "isopygy" in this case would refer to the similar adaptations for arid survival. Identifying isopygy is crucial for understanding the power of natural selection and the constraints imposed by ecological niches.