Hi, Richard, I just noticed that I haven't paid close enough attention to the mtDNA cladograms of Rodriguez-Robles. Up to now, I have treated the Sierra Nevada snakes as presumptively large morph and that they form a single lineage. It turns out there are two sublineages within the Sierra Nevada subclade. Specifically, genetic data shows that the specimens from loc. #15, #17, #18, #19 and #26 (Tulare Co.) represent an older lineage than the sublineage which consists of Kern County dwarf boas plus the remaining Sierra Nevada snakes, including loc. #16. Based on genetic data, there is a chance that snakes from #15, #17, #18, and #19 and #26 (Tulare Co.) may be dwarf morph snakes. It may be worthwhile to have a look at these voucher specimens to verify their morphology. If they turn out to be small morph, then we may have both small morph and large morph boas living in the Sierra Nevada range. This sublineage (#15, #17, #18, #19 and #26) appears to have migrated northward along the Sierra Nevada at a slightly earlier time period than the boas from other localities that are large morph.

If boas from loc. #15, #17, #18, #19 and #26 turn out to be large morph snakes, then one possible explanation is that despite their earlier arrival in the northern part of the range, their small morph phenotype was later swamped by the large morph phenotype that arrived later. The phenotype of the small morph early arrivals died out, leaving only the mtDNA of their small morph ancestors. However, based on your captive breeding data, a female dwarf morph would only produce offsprings with the dwarf morph phenotype, even when mated with a large morph male, therefore it is difficult to see how her mtDNA will get passed on to a large morph snake, since all her offsprings will be small morph and mtDNA is matrilineal in descent. If a dwarf morph phenotype F1 individual can produce large morph offsprings when back crossed to a large morph male, however, that could result in large morph snakes with the ancient small morph mtDNA haplotype.

A second explanation (if this early sublineage is large morph)is that the males from this sublineage dominated mating of later arriving snakes which may be small morph. Subsequently, natural selection favored the large morph individuals, and the small morphs snakes died out, leaving only the large morph snakes we see today. This explanation is less likely by the way than the first one.

To solve this mini-mystery, it is important that morphological data be obtained from both the voucher specimens at loc. #15, #17, #18, #19 and #26 to ascertain whether they are large or small morph. Morphological data from the captive crosses between small and large morph boas are also needed. For now, C. bottae taxonomy is even more complicated than I had previously imagined.

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