The phylogenetic relationships of the Hemerocallis species is an interesting if sometimes confusing subject. This old genus of Asparagales monocots has been in proximity to humans for some tens of thousands of years, modern man having been in Asia since at least 50.000 y. a., and Hemerocallis appearing to have been there for more than 25 million years.
Hemerocallis has been an agricultural crop in much of Asia for a couple of millennia, if not longer. For me, this long term potential for intermingling of captive-selected, feral and true, wild-species materials leads to potential admixing and selection for type that might not happen in fully wild conditions with no human intervention.
Many Hemerocallis species can easily be transported long distances with high survivability and adaptability. This is especially true of some of the fulva group, but also for several of the yellow species. This leads me to suspect that original species ranges have long since been blurred. For that reason, I prefer to look at the species of the genus Hemerocallis in the most minimalistic terms. It is important to stress that this is not a scientific thesis, but rather a collection of my thoughts and observations about the genus Hemerocallis and the pre-domestication materials that we might refer to as 'the species'.
I am making no attempt here to lay out a new understanding of the speciation of the Hemerocallis. I am intentionally using the most minimalistic way of understanding the two categories that the species fall within - "orange" and "yellow". This allows me to speak in more general terms and leave specifics to those with the expertise to pursue such matters.
While I may discuss where I think species boundaries may fall in some instances, this will not be my primary concern in this article. Much more work needs to be done on the phylogeny of the Hemerocallis before we can make any certain statements, but based upon current models, we see two major divisions early on in the Hemerocallis - orange and yellow. Another split seems to consistently lie within the yellows creating two major sections of yellow flowered types, but from which no clear patterns of phenotype emerge to me, as yet, with those said to clade together. I will give more consideration to possible species with the yellows than I will with the fulva group, as I think the only speciation within the fulva group is toward H. sempervirens and H. aurantiaca (or away from them). Otherwise, I think the fulva complex is composed of regional variations and garden selections - forma - not subspecies or species within an over-all 'fulva umbrella'.
I do acknowledge that there are likely to be several species amongst the yellow branch of the Hemerocallis genus. However, I think the fulva clones (or forma) all comprise one species with many regional and garden variations, clones or forma (forms). I do think that H. sempervirens and H aurantiaca are offshoots of the fulva complex, though they also could represent ancestral, evergreen types. I simply do not know, but would encourage research to elucidate this relationship more fully. Perhaps these are in the process of speciating or perhaps they represent older, evergreen ancestral forms. It is interesting to ponder.
I do suspect that sempervirens and and/or aurantiac are of fulva origin, one way or the other, and they group with the fulva in the clades I discussed in part 1 of this series - What is a Daylily? The Genus Hemerocallis. As I am not a phylogeneticist, I am making no attempt to reassess the current species designations, but it seems some reconsideration may be necessary in the future. That however will be up the the phylogeneticists. I will use the species names as presented within the paper from which it derives, when discussing species.
That does not mean that a plant labeled as one species is the same exact clone as that used in another project and called the same species: there is much regional variation between species, and there are numerous forms of the species in commerce and agriculture, as well as the variations that occur naturally within the wild populations of the species. I must stress that I find the entire species structure of the Hemerocallis to be tenuous, formed on the old field-identification methods of the last three-centuries, as it is.
Now, with genetic analysis we can make much more certain comparisons, and no longer need to compare visual presentation in an attempt to determine relation. We can begin to look beyond form and understand the actual genetic relationships. With that said though, much more extensive research is needed to unlock a broad-based phylogenetic analysis. What we have now in the papers listed at the end of Part 1 is a good beginning to point us in the direction of further research and give us a starting point to piece together this complex web of relationships.
In the papers I cite at the end of Part 1 concerning the phylogenetic trees of the Hemerocallis species, there tended to be two major splits - orange and yellow - the fulvas and all the yellows comprising two different major clades. Then within the yellows, there are typically two major breaks with several species in each branch.
Tomkins showed H. citrina vespertina to be at the base of the separation of the yellow and fulva types. The vespertina species may be suggested then to be older than other yellows and may be ancestral to all of them, as McGarty suggests in his analysis Phylogenetics, DNA, Classification And the
Genus Hemerocallis. Further data may refute this, but the phylogeny that the Tomkins tree presents is certainly suggestive and interesting.
Some of the yellow forms are nocturnal, but certainly many are diurnal. The plant of H. citrina vespertina that I grow is nocturnal. My plant derived from Joseph Haliner. I can say nothing as to how this plant would compare to the plant in the Tomkins study.
The next major split in Tomkins would suggest that H. citrina is older than and possibly ancestral to H. minor, H. hakuunensis, H. dumortierii and H. middendorfii, while on the other side of the split is H. lilioasphodelus and it is shown to be older than and possibly ancestral to H. thunbergii and H. dumortierii var. Sieboldii.
In Genetic and Phylogenetic Relationships of Genus Hemerocallis in Korea Using ISSR by Choi, et al., the phylogenetic tree shows fulva and fulva for. kwanso as clading with H. middendorfii, while H. dumortierii clades with H. thunbergii and H. minor. Another earlier branch from the yellow group give H. coreana and H. hongdoensis, both Korean forms that have been given species status.
In the paper Phylogenetic Relationships of the Genus Hemerocallis in Korea using rps16-trnK Sequences in Chloroplast DNA by Man Kiu Huh, et al., There are three phylogenetic trees presented. The first tree is a ps16-trnK analysis using MEGA5 and shows H. fulva var. kwanso at the bottom position within the tree. From there a branch occurs that contains two forks to H. coreana and H. aurantiaca, while another branch leads to all the yellows - H. minor, H. littorea, H. thunbergii, H. dumortierii var. esculenta and H. dumortierii. H. coreana and H. aurantiaca usually show the dark 'gold' coloring that is similar to the center petal pigmentation of many fulva types - rich in carotenoid pigments.
In the second phylogenetic tree - rps16-trnK analysis using PAUP 4b10 - the divisions occur in the same manner as in the first tree from figure 1.
When the third tree is formed using PAUP 4b10, we see a shift of the layering of some of the forms involved. While the yellows hold their form from the other two maps, the positioning of H. aurantiaca, H. coreana and H. fulva var. kwanso shift, with aurantiaca at the base, coreana representing the next branch and fulva var. kwanso next and from there the large group of yellows branch off. Even with these discrepancies, we can still see that the basic break of "orange and yellow" holds up fairly well.
In synopsis, it is my view that these relational phylogenetic trees give us a glimpse into the evolutionary history of the genus Hemerocallis. Each paper reinforces the notion of the two main groups - orange and yellow.
The fulva complex represents the use of both carotenoid and anthocyanic factors to make the more heavily pigmented flowers which include visible eyes and midribs. Both the under layer of carotin within the petal and the top layer of anthocyanins are present in most examples. Some forms in the var. rosea category within the fulva complex show reduction of carotene within the petal and a change from the typical orange pigment to a visually pink pigment in the petals. Other forms show intensification of red, while other forms show particularly bright and clean orange tones. Yet others have a purple overlay and present a brownish, fulvous coloring. Fulva complex forma are almost certainly responsible for the majority of anthocyanic colors and patterns seen in they highly-selected hybrid garden daylilies.
The yellow flowers show various levels of changes from the flower color of the fulva group. The most conspicuous change is that the surface anthocyanins seem to be lost and so the under pigments in the middle of the tepals is highlighted, becoming the "coloring" of the flower, the exact tone depending on the combination, presence and/or absence of carotenes and other yellow/gold pigments.
These flowers appear 'self colored' or solid in color and range from darker, orange golds (H. middendorfii, H. coreana, H. hakuunensis) to medium yellow gold (H. dumortierii) to yellow (H. minor, H. citrina) to light yellow (H. vespertina and H. citrina forms) to very pale yellow (H. citrina 'Baroni', other H. citrina clones). It seems to me that the range of yellows may have to do with the removal of carotenoid pigments found in the tepals that create the deep orange/gold/yellow coloring of forms such as H. dumortieri or H. middendorfii and underly most fulva forms, creating a rich pigmented area under the upper anthocyanic layer within the main body of the tepals in most fulva forma.
As these pigments are knocked out, the lighter-appearing yellow pigments are expressed without any interference - sort of a natural "color clarification" process. The palest forms of citrina and vespertina would then represent the most reduced pigmentation amongst this group.