Do you suppose there are subtly different types of Andalites, for example, depending on where they're from on their planet?
Andalites don't appear to me as a species who is too keen on adapting to the environment. In the Andalite Chronicle the Andalites was surprised to know that humans weren't "kept out of a place just because the weather's bad" so I guess Andalites only live in parts of the planet where the environment suit them the best. As the result the differences between their races will not be as significance as in human's.
The thing is, though, that all species do this on some level. Any species will tend to spread out as much as it can, to get away from competing individuals, and often has to adapt to new environments in the process. For the dominant species on a planet, and for open-space-requiring grazing animals, this is
especially true.
It's just not something anybody talks about in normal conversation. A guy might say, "Who would want to live in Egypt? It's way too hot there," rather than saying, "Hey! I could adapt to Egypt's climate and go there!"
Finally, it's impossible to adapt to every environment simultaneously. So no matter what kind of Andalite you are (if Andalites have racial differences, that is), there would be some sort of environment that would be not be ideal to you. Thus, the quote from the Andalite Chronicles.
Or, I suppose it is possible that the Andalites once had racial differences, but don't anymore, thanks to enough interbreeding between races. Give our own planet long enough, and we're probably headed in the direction of one giant mixed race, too.
Nevertheless the idea is a valid one, it makes sense so there probably would be differences, in fact isn't it sort of implied that the yeerks and the race the Animorphs saved from the howlers were likely once relatives that evolved apart? I don't remember that race's name, it's been too long -_-
You're thinking of the Iskoort. The Yoort portion of the Iskoort split off from the Yeerks and evolved into a different species.