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How does the biological species concept use interbreeding and reproductive isolation?

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Marble bust of Aristotle with a beard and draped robe, showing detailed facial features and wavy hair, set against a dark background. — Philosophy of biology Detail of a Roman copy (2nd century bce) of a Greek alabaster portrait bust of Aristotle, c. 325 bce; in the collection of the Roman National Museum.

In the philosophy of biology, the biological species concept defines a species as a group of natural populations whose members are capable of interbreeding and are reproductively isolated from other such groups.12

The Role of Interbreeding and Isolation

Interbreeding: This concept posits that members of the same species share a common gene pool, allowing genetic changes to spread through the population via sexual reproduction. Successful interbreeding is defined by the ability to produce viable, fertile offspring.12
Reproductive Isolation: This is the mechanism that maintains the boundaries of a species. It ensures that species remain independent evolutionary units by preventing gene flow between different groups.13

Reproductive Isolating Mechanisms (RIMs)

Biological properties that prevent interbreeding are known as reproductive isolating mechanisms (RIMs), which are categorized into two types:4

Prezygotic RIMs: These prevent fertilization from occurring through ecological, temporal, behavioral, mechanical, or gametic barriers.4
Postzygotic RIMs: These take effect after fertilization, resulting in hybrids that have reduced viability or fertility (such as the sterile mule).42

While this framework is foundational, it faces philosophical and practical challenges, particularly regarding asexual organisms, fossil records, and "rings of races" where reproductive compatibility varies across populations.51