The fabulous colors in the bracts of the Castilleja shown on this page never cease to amaze me -- and everyone else!
Most floras consider this taxon to be the result of present-day hybridization between Castilleja rhexiifolia and Castilleja septentrionalis. Arthur Cronquist, however, stated, "There is little evidence of hybridization". Cronquist pointed out that hybridization is unlikely because Heckard and Chuang (1977) determined that the two species "are usually of different ploidy levels".
The floras that indicate there is present day hybridization give no supporting evidence for hybridization, and I can find no research with supporting evidence. On the other hand there is evidence, such as that presented by Heckard and Chuang, that indicates that the multicolored bract taxon is a distinct species. I find this evidence compelling and therefore propose the name, "Castilleja versicolor" for this distinct species. I am working now on a publication of this new species.
Here are two further key pieces of evidence that support species status:
1) At least in the western San Juan Mountains of southwest Colorado the two putative parent species often occupy different elevations: C. septentrionalis grows in the montane and lower subalpine and C. rhexiifolia in the high subalpine and (primarily) in the alpine. The Castilleja with multi-colored bracts is found growing by itself or (more commonly) growing in the company of C. rhexiifolia, rarely in the company of C. rhexiifolia and C. septentrionalis.
2) Far more important is the Genetic research by Hersch-Greene and Cronn which supports the distinctiveness of this taxon. This research concludes:
"Cumulatively, molecular data points to a pattern of distinctiveness—not hybridity—in the putative hybrids because they are as genetically distinct from C. miniata, C. rhexiifolia, or C. sulphurea [now known as C. septentrionalis] as any of the three species are from each other".
"If the putative hybrids resulted from recent and ongoing hybridization, they should show intermediate and/or variable ploidy levels; we found no evidence for either of these patterns".
"In light of the discussion, we believe that hybridization, followed by genomic reorganization, provides a likely explanation for the unique and uniform genetic identity of the field-classified hybrids. It is at least as parsimonious as the alternative, namely, that field-classified hybrids represent a species of nonhybrid origin that has maintained multiple color alleles over time. The latter scenario would require variation in color alleles be selectively maintained or linked to other adaptive traits. Molecular data from neutral and nonneutral markers (i.e., Antirrhinum color pigmentation genes, Whibley et al., 2006) and from more Castilleja species that occur in this region of Colorado are needed to better assess the origin of these field-classified hybrids. If our hypotheses are correct, the parentage of field-classified hybrids seem most likely to include plants similar to C. rhexiifolia and C. sulphurea, with little contribution from C. miniata."