Hi, you have a very good grasp of the concept of budding. However, budding usually refers to the origin of new species or new higher taxa, not the origin of new geographic races. Therefore the rubber boa may not be considered an example of budding unless a new species is recognized.

Indeed, the common ancestor of both the large and small morphs of the rubber boa can either be a large morph, a small morph or something totally different. However, given the fact that both the large morphs and the small morph are morphologically very similar, it is extremely unlikely that their common ancestor would be very different morphologically from either of these.

Therefore the only question that remains is whether this ancestor is large or small morph. A possible answer to this question comes from the fact that umbratica is the first lineage to branch off from this ancestor. Since it branched off first, this lineage is most likely to retain the ancestral characters found only in the common ancestor of all rubber boas, but it will not have any of the characters of the next lineage to branch off. A lineage which branches off later may contain features found in both the ancestral and the new lineage. For example, in the evolution of the Chordata, the primitive chordates retain the ancestral character of the notochord but lack the more recently evolved characters of lineages that diverged later such as limbs. The lineage leading to birds, for example, diverged much later, and so it has both limbs and the notochord (at least in some part of the life cycle).

We see that umbratica (the first lineage to branch off) consists only of small morphs and the Sierra Nevada subclade (which branches off later) consists of both large and small morphs. Applying the general principle discussed above to the rubber boas, it is most probable that the small morph is the ancestral morphotype since it is found in umbratica, the oldest lineage and that the large morph evolved later since large morph snakes are found only in the newer lineages (Northwestern and Sierra Nevada subclades).

If umbratica is considered a different species, then bottae indeed budded off of umbratica since umbratica continues to exist and is now a paraphyletic species. The problem with recognizing umbratica as a new species is that some of the small morph populations, which is morphologically indistinguishable from umbratica even on the basis of adult size would be classified as a different species: bottae.

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