What exactly is a subspecies? A consensus approach?

[Mgellis]

I know that the term "subspecies" does not really have a precise definition, but I was wondering if there was a kind of consensus used by biologists.  I imagine there is a kind of "critical mass" of difference where most people look at two animals and say, "yeah, that's not just two different animals anymore; those are actually different subspecies."  But where is the line?  Yes, obviously, it must vary from case to case, but are there any guidelines that biologists use?

Also, I know that "breed" implies human intervention.  But why are breeds not subspecies?  Why, for example, are Shiba Inus and Beagles not separate subspecies?  Is it simply that they don't occur without human intervention? 

Thanks.

 

[iNow]

Biologists tend to realize that any category we invent will be imperfect and nearly always will have exceptions.

They are open to interpretation and often if you ask 10 different people what is a species or subspecies you’ll get 10 different answers.

The categories are not rigid and are only applied if and when they useful to whatever outcome we’re trying to achieve, but it’s not exactly like Mach 1 where you know that if you accelerate just 1 more mph then THAT is when you’ll break the sound barrier. 

https://evolution.berkeley.edu/evolution-101/speciation/defining-a-species/

[sethoflagos]

On 9/6/2023 at 8:35 PM, Mgellis said:

I know that the term "subspecies" does not really have a precise definition, but I was wondering if there was a kind of consensus used by biologists.

Having just finished reading Richard Dawkins' The Ancestor's Tale for I think the third time, I think that he would express a subspecies as something along the lines of:

Quote

A natural population that has had sufficiently low gene exchange with the parent population for a sufficient length of time for the evolution of significant phenotypic differences to have become fixed within the two groups while still maintaining the potential to interbreed naturally.

The term 'fixed' distinguishes subspecies from 'morph' which would apply to a phenotypic character that only occurs in a part of a given population. 

Edited September 12, 2023 by sethoflagos
Clarification