Convergent evolution

Convergent evolution is the independent emergence of similar traits in distinct lineages, often because similar environmental pressures favor similar solutions.

Natural selection: The process by which heritable traits that improve reproductive success become more common in a population. Similar selective pressures can favor similar adaptations in lineages that evolve independently.
Placental and marsupial mammals: Two major mammalian groups whose lineages diversified separately after their ancestors diverged. Their independent radiations produced strikingly similar ecological forms.
Phylogenetics: The study of evolutionary relationships among organisms, genes, or other biological entities. A phylogeny tests whether similar traits arose independently or were inherited from a common ancestor.
Evolutionary predictability: The extent to which similar evolutionary conditions produce similar outcomes across independent lineages. Repeated convergence provides evidence that evolution can be predictable under some conditions.
Evolutionary constraint: A limitation on the evolutionary changes available to a lineage, imposed by factors such as development, genes, or history. Shared constraints can channel separate lineages toward similar forms.
Ichthyosaurs: An extinct group of marine reptiles with streamlined bodies and paddle-like limbs. Their body shape resembles that of dolphins despite a distant relationship.
Homology: Similarity between biological features because they were inherited from a common ancestor. Homology is the alternative explanation when resemblance reflects shared ancestry.
Homoplasy: Similarity among traits that arose independently rather than through inheritance from a common ancestor. Convergence is one form of homoplasy, alongside evolutionary reversals.
Adaptive landscape: A model mapping genotypes or phenotypes to reproductive fitness across possible evolutionary outcomes. Separate lineages can reach similar high-fitness regions under comparable conditions.
Cacti and Euphorbia: Plant groups that independently evolved succulent stems and spines in dry environments. Their resemblance arose in separate families under similar arid conditions.

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