How could you show that Labradors and Border Collies both belong to the same species?

Labradors and Border Collies both belong to the same species, Canis lupus familiaris, as they can interbreed and produce fertile offspring. Genetic studies reveal that they share a high degree of genetic similarity, reflecting their common ancestry. Additionally, they exhibit similar behavioral and physiological traits characteristic of domestic dogs, which further supports their classification within the same species.