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First, it's important to distinguish between genotype and phenotype. Most genetic mutations don't cause any change in behavior or appearance, so the two individ

First, it's important to distinguish between genotype and phenotype. Most genetic mutations don't cause any change in behavior or appearance, so the two individuals are phenotypically equal. With sexual reproduction, individuals can differ genetically but still be compatible, so there is some notion of a pool with a clear boundary. For viruses, this is of course a bit trickier because they "reproduce asexually"[0] and quite rapidly, so mutations happen at a high rate. But one useful property to distinguish them is which receptors (and thus which cells) they bind to, generally affecting what symptoms and diseases they cause. [0]: Viruses are not considered living things, so the concept of reproduction is already quite a stretch.

littlestymaar 7y ago
> so there is some notion of a pool with a clear boundary. That's a model that kind of works most of the times, but not always: the most known example are Bisons and Cows which can breed together and the offsprings are fertile : https://en.m.wikipedia.org/wiki/Beefalo https://en.m.wikipedia.org/wiki/Beefalo In fact, most of today's bisons have cows' genes in their genome.
dragontamer 7y ago
> With sexual reproduction, individuals can differ genetically but still be compatible, so there is some notion of a pool with a clear boundary. The boundary isn't very clear. https://en.wikipedia.org/wiki/Ring_species https://en.wikipedia.org/wiki/Ring_species A can breed with B, B can breed with C, C can breed with D, and D can breed with A. But A cannot breed with C. Are A and C part of the same species, or not? These "ring species" occur around geographic rings, such as the Arctic Circle, so each population remains genetically compatible with its neighbors... but not "across the ring". https://upload.wikimedia.org/wikipedia/commons/thumb/8/8d/Ring_species_seagull.svg/800px-Ring_species_seagull.svg.png https://upload.wikimedia.org/wikipedia/commons/thumb/8/8d/Ri...
- throwaway5466 7y ago
  Yeah. Basically the concept of species is bust taxonomically and largely a social construct at this point. (That is to say, what is a species is what the community agrees to be a species for the sake of convenience)

littlestymaar 7y ago

> so there is some notion of a pool with a clear boundary. That's a model that kind of works most of the times, but not always: the most known example are Bisons and Cows which can breed together and the offsprings are fertile : https://en.m.wikipedia.org/wiki/Beefalo https://en.m.wikipedia.org/wiki/Beefalo In fact, most of today's bisons have cows' genes in their genome.

dragontamer 7y ago

> With sexual reproduction, individuals can differ genetically but still be compatible, so there is some notion of a pool with a clear boundary. The boundary isn't very clear. https://en.wikipedia.org/wiki/Ring_species https://en.wikipedia.org/wiki/Ring_species A can breed with B, B can breed with C, C can breed with D, and D can breed with A. But A cannot breed with C. Are A and C part of the same species, or not? These "ring species" occur around geographic rings, such as the Arctic Circle, so each population remains genetically compatible with its neighbors... but not "across the ring". https://upload.wikimedia.org/wikipedia/commons/thumb/8/8d/Ring_species_seagull.svg/800px-Ring_species_seagull.svg.png https://upload.wikimedia.org/wikipedia/commons/thumb/8/8d/Ri...

throwaway5466 7y ago
Yeah. Basically the concept of species is bust taxonomically and largely a social construct at this point. (That is to say, what is a species is what the community agrees to be a species for the sake of convenience)