The Hemerocallis belong to the order Asparagales (often referred to as 'Asparagoid lilies') and is in the family Xanthorrhoeaceae. The order of Asparagales are considered monocots, which is one of the two large monophyletic groups most plants are divided into based on the number of leaves at time of germination: plants that usually only generate one leaf or one cotyledon, are generally considered monocots. The Hemerocallis are lilioid monocots, characterized by having colored flower tepals on various sizes and expressions of flowers. The hyperlinks in the text for Asparagales and monocots are linked to the Wikipedia pages for those terms. They are good repositories of information and you should read over them if the subject interests you.
All of the Hemerocallis species seem to originate in Asia, specifically from China east of the great deserts to the west and into northern and southeastern to southwestern China, down into the foothills and valleys of the Himalayan Mountains in Tibet and on down into northern India, then on east to Korea, Taiwan and Japan with species of Hemerocallis ranging from the extreme northern islands of Japan to the small southern-most islands of the multi-island country. The islands off the coast of southern China are also populated by Hemerocallis species. While I do not have any references to wild populations of Hemerocallis in Vietnam, Laos, Cambodia, Thailand or Myanmar, or further south into the islands of equatorial Asia - the Philippines, Malaysia and Indonesia, I would be surprised if some of the daylily species aren't grown in many of these countries. I do not as yet know the southern maximum for radiation of Hemerocallis species in the recent historic past - modern times before the beginning of hybrid Hemerocallis breeding for garden flowers. Nor whether that was through natural processes or through human intervention with several daylily species being good candidates for the production of food and easily transported as trade items. This is a subject I hope to gather more data on in the future.
At the other extreme some species are found as far north as Siberia. Species such as H. minor and H. dumortierii are found in the boreal forests of Siberia, in the sub-arctic. The Gobi desert may have cut off populations in the far north from populations further south, creating unique populations of the same basic stock. The species clone Hemerocallis fulva 'Europa' seems to have moved from Asia into the Middle East, the Mediterranean and Europe over many centuries, arriving in Europe in the 18th century or earlier, while the species H. lilioasphodelus has been in Europe even longer, specifically in Greece where it has been grown for about two-thousand years. However, it seems the origin of the genus Hemerocallis lies in Asia. It seems likely that these two forms made their way to the Middle East and Europe through trade, possibly through ports or the silk road.
The monocots are said to go back to the early Cretaceous period (perhaps as far back as 120 m.y.a.) and the Asparagales are thought to branch off from other monocots in the early Cretaceous, making them a very old branch of flowering plants from the monocot group. For this reason there is much diversity in both the monocots in general. There are a host of traits that make monocots different from other plants and there are traits that make the Asparagales different from other monocots.
It is not known exactly how long ago Hemerocallis emerged from the Asparagales lineage. I have found a reference to the genus in 'Early Cretaceous lineages of Monocot Flowering Plants - Bremer, et al., 2000. Their paper records their use of DNA sequence data to determine the ages of splits within the phylogenetic tree of the monocots. The chart in figure 1 shows the Asparagales go back past 100 million years in their arrangement. The Hemerocallis appear to go back to about 35- 40 m.y.a. and find their origin in the middle of the Paleogene period, the Eocene Epoch.
I also found a reference from the abstract from 'The historical evolutionary development of Hemerocallis middendorfii (Hemerocallidaceae) revealed by non-coding regions in chloroplast DNA by J. Noguchi, D.-Y. Hong and W. F. Grant - Plant Systematics and Evolution - Vol. 247, No. 1/2 (July 2004), pp. 1-22, to the split between geographical populations of H middendorfii. The abstract to the paper suggests that the populations of H. middendorfii were split apart when the Sea of Japan formed, separating the two groups - one in China and the other in Japan. The authors estimate this split using molecular testing and geographic history. They estimate that split to have occurred approximately 25 million years ago at the end of the Oligocene epoch, at the end of the Paleogene period.
We may have good DNA and geological evidence that Hemerocallis goes back at least to the end of the Oligocene epoch at twenty-five million years ago. The entire genus must be as old as the species H. middendorfii, if not older, perhaps even going back to the middle of the Paleogene period as suggested by Bremer, et al.
Paleogene period/Eocene epoch
The Paleogene is characterized as the time after the Cretaceous extinction event where dinosaur populations end and mammalian and avian species arrive on the scene and diversify, the monocots and dicots diversify also. The phase of the Paleogene when the Hemerocallis have been suggested by Bremer to emerge is the Eocene.
The Eocene began as a warm time in which much of the world was covered in tropical forests. It would end, becoming the Oligocene, in a greenhouse to ice-planet swing over the course of the Eocene. Swings between cold and warm continued into the Oligocene and throughout the Neogene, in which we are in the latest interglacial warm period.
The cooling during the Eocene is thought to begin around 49 m. y. a., which is somewhat earlier than Bremer, et al., suggest the split for Hemerocallis, and could suggest that Hemerocallis emerged during the beginning of the Eocene cold period. We certainly can't say for certain at this time when exactly Hemerocallis first emerged, but Bremer is suggestive, and while new information could change the dates somewhat, the two pieces of evidence that I sight above seem to indicate a lineage of at least 25 million years ago or (most likely) much more, possibly with a target in the 35-40 m. y. a. range.
The evolution of the ancestral Asparagales that led to the Hemerocallis occurred in the vast tropical forests of the early, warm Eocene period. With the rise of the Eocene cold period the Hemerocallis-ancestors of those tropical forests would have had to adapt to the colder conditions and the early forms of Hemerocallis would have needed to be able to survive through cold periods, but also survive during the warm periods that have occurred between the extreme cold periods, with this cycle increasing about 2 1/2 million years ago during the rise of the Quaternary Glaciation (we are in the latest interglacial of the Quaternary at this time). In areas where tropical warmth occurs even during cold periods (such as glacial refugia during ice ages in areas toward the equator and below (or above) the boundaries of the glaciers), tropical species could persist even in the coldest ice ages of this period. In areas that have seen long cold periods followed by long warm periods, survival can be achieved by being able to express both deciduous and non-deciduous trait, with the expression depending on environmental triggers that allow the plant to grow or go into dormancy to conserve energy and survive very cold and very hot periods.
We still see this behavior in many daylily species, including but not limited to, many forms of H. fulva and the H. citrina types. During the time in which the Hemerocallis appear to have been around, we have seen extreme planetary climate change, many times, from glacial to interglacial periods of warmth and heat, with the worst cold glacial periods being in the Quaternary. During the cold periods there are generally some warm refugia. There were glacial refugia in both Old World and New World. Warm refugia occurred around the equator in the Quaternary in Asia, Australasia, Polynesia, the Americans with areas in both continents, and the Mediterranean including parts of Southern Europe to the Indian Ocean and the Persian Gulf in Western Asia. Much of Asia was warm. Glaciation at the height of the last glacial maximum (before 12-13 thousand years ago (t. y. a.)) did not cover much of Asia, descending down into Siberia, but not fully down into China or even Mongolia, though much of northern China would be temperate, great swathes of Asia were large, warm ice-age refugia. Glaciers extended much further south into the North American continent than they did in the Asian continent and they extended deep into Eastern Europe/Western Asia above the Current Black Sea. Refugia in North American would have extended from approximately modern day Cincinnati, Ohio south.
It is also important to remember that in the glacial maximum periods, the water level decreases in the world's oceans, being trapped in massive glaciers, and many parts of the continents are exposed that are under water in our interglacial age. So in addition to the large modern day landmass that was not glaciated in Asia, there would have also been large swathes of lowland such as the Sunda Plain, which is now the site of the Sunda Straits, which is over top the Sunda Shelf, which was exposed during much of the last ice age up until about 12 - 13 t. y. a. Current Hemerocallis species elevations would have been significantly different only 12 - 13 t. y. a. One wonders how many species were lost under the rising seas at the end of the last ice age.
The Hemerocallis genus may have survived by being generalists that could deal with both warm and cold conditions, high and low elevations and a wide range of soil types, while exploiting those conditions to generate nutrients (or make use of a wide range of available nutrient sources). The flora and fauna most capable of surviving geological and climactic changes tend to be generalists. Specialists are much more vulnerable because they have adapted to very specific sets of conditions to which they may not be able to survive without, while generalists can survive under a broader range of changing conditions. When conditions remain consistent for long periods of time, specialists can survive for long periods of time giving them the veneer of 'survivability', but if conditions change over vast geological scales, the form can decline being unable to adapt to long term changes. Asia, with its large refugia and large tropics would have led to some strains of tropically adapted Hemerocallis species (such as some of the specialized species from the southern-most, tropical islands of Japan - H. sempervirens, etc.).
Other species, such as H. minor, which is still found as far north as the boreal forests of Mongolia and Siberia, may well have been in those ranges for many, many millions of years. Though they could also be from repopulation at any time during the Quaternary interglacials. They thrive very far north as a handful of other species do as well. The greatest number of species seem to fall in a swath across central and southeastern China, Korea, across to Japan and down to the islands off the coast of China (Hong Kong, Taiwan, etc) then over to parts of the Indian subcontinent and into the Himalaya, especially on the Northern side of the Himalaya which borders on Gansu Provence in the Southwest of China, which is well-known for plant production and its many types of anciently-cultivated plants and its many types of unique wild flora, as well.
Before the end of the last ice age, there was considerably more land above water all around the Chinese coast, up to the Korean peninsula and around Japan. Korea and Japan were much increased and much closer to each other. Many of the current day islands were all connected and connected to the mainland or large islands. The Japanese islands were one landmass at that time. That may indicate that the current populations descend from populations that were at higher elevations in the last ice age. Many current Hemerocallis species can survive in the wild in a diverse range of conditions. Many exploit high altitude ranges but also easily adapt to lower altitudes. Most daylily species seem to be able to tolerate low-water conditions, but the vast majority flourish when they are grown in less-dry conditions. As in the species, our modern hybrids show this same pattern wherein there are very few actual dry-thriving forms, but many forms that will survive a dry period and not reduce or cease to exist, but won't flourish or look very good. Foliage on both species and hybrid forms of Hemerocallis can look terrible, and this is a common survival strategy - for the foliage to die in severe conditions, either extreme heat or cold, as well as dry conditions. There are however amongst both species and hybrids those that suffer more when water rations are reduced below a certain point, while some few will retain an attractive appearance much longer under water rationing or drought.
When we want to consider the current forms of Hemerocallis species that are demonstrably generalists, we want to look at those that survive and flourish in the widest range and seem to have done so for a very long time. This would include first and foremost the fulva forms, which are very widely distributed, especially forma 'Europa', which is now naturalized through many areas of the world. Many other forms of fulva exist in Asia and this is a huge group of often quite robust plants, especially those that are triploid. Fulva occurs in both diploid and triploid forms. They also qualify as strong generalists in many of their forms, able to survive in wild states, often forming large mats in wild conditions. In addition to the fulva group, the small yellow dayliies, called H. lilioasphodelus, H. Minor, and H. dumortierii are widespread throughout the world as well as in the wild in diverse ranges.
The modern species are interesting, but are difficult to make absolute statements about. In China and most of Asia, there has traditionally been two major divisions for Hemerocallis types - orange and yellow, with a further division in the yellow group for small yellow and tall yellow. I would agree that this division - orange and yellow - seems to be a real point of division representing the evolutionary history of the Hemerocallis genus. Gene testing has shown there to be two major clades of Hemerocallis. Interestingly, these major clades fall along the 'orange and yellow' categories. One major split from the ancestral form of Hemerocallis lost anthocyanin pigments becoming self gold to yellow in various shades, with no eye an little to no midrib. When viewed in the ultraviolet spectrum, most of these "self" colored yellows and golds show intense eyes that glitter with color. But we cannot see them in our limited visual range. We perceive a self colored flower missing anthocyanin. We can't see it, but that doesn't mean it isn't there, in some way, even if suppressed in certain pigment ranges. This line split from the fulvous, anthocyanic line very early on and the two lines have evolved forward since.
I have found three phylogenetic trees done in different research projects on Hemerocallis species using genetic comparison to group clades of relationship. These studies have been consistently similar in showing a deep and early split between the fulva family and the yellow family. The relationships within the yellow group shows two major forks within it. However, height is not consistent between any of these two groups of yellows.
The papers are as follows:
A google search of any of these titles should bring up the papers, references or places where the articles may be obtained.
DNA Fingerprinting in Daylilies - Genetic Variations and Relationships among Species - Part 2
Daylily Journal Vol. 56, No. 3 Fall 2001 - Jeffery P. Tomkins - Clemson University Genomics
Man Kyu Huh *, Oh Sung Kwon , and Byeong Ryong Lee
Department of Molecular Biology, Dong-eui University, Busan 614-714, Korea
Department of Biology Education, Seowon University, Chungbuk 361-742, Korea
Received January 24, 2013/Revised May 20, 2013/Accepted June 28, 2013
Genetic and Phylogenetic Relationships of Genus Hemerocallis in Korea Using ISSR
Joo Soo Choi, Hong Wook Huh, Seol-A Lee and Man Kyu Huh
Department of Biology Education, Pusan National University, Busan 609-735, Korea
We will look at this in greater detail soon when I write about the species from historical times.
So what is a daylily?
It is an Asparagales monocot of the genus Hemerocallis. The Asparagales contain many interesting plant families. In addition to Hemerocallis, the group also contains orchids (Orchidaceae), irises (Iridaceae), Hosta (Agavoideae), Amaryllis (Amaryllidaceae), Agapanthus (Agapanthoides), Allium (Allioideae), and of course Asparagus (Asparagaceae) among many others. The Amaryllis clade and the Asparagus clade are connected from a common branch that is very deep in the ancestry of the Asparagales and represent a deep split with all the other Asparagales families. The Hemerocallis comes from that other line.
The Hemerocallis, along with all the Asparagales, are very old lineages of perennial flowering lily-like grass-relatives (monocots). They are often generalists that can grow in many biotypes. There are two main groups within the Hemerocallis - those which show anthocyanic, water soluble pigment in the upper layers of the tepals, usually in orange in the wild species, characterized as the fulva clade. The other main clade doesn't show visible anthocyanin in the upper layer of the tepals, though eyes and mid-ribs are visible in many in the ultraviolet spectrum that many birds and insects (pollinators) see. It remains to be seen in the case of the pattern visible in the ultraviolet spectrum if the pattern is the result of a pigmentation or a refraction effect. To our eyes though, this second line of Hemerocallis appear to be single colored yellows and gold.
The Hemerocallis have been cultivated in Asia for millennia. The main use is for food in the form of dried flowers for soups and other dishes, and there are other food applications also. There are reputed medicinal properties and some research suggests this may be true. Many different forms of many species are grown in cultivation in many parts of Asia. There are likely to still be wild populations of species in many parts of Asia. Some of these could be escaped cultivations. It is very hard to discuss specifics of the species because they have been cultivated by man for so long. Many of the forms that we attempt to call "species" or even "clones" may represent garden forms, bred or (more likely) accidentally produced within captivity, rising to prominence for one or many reasons. The age of the genus, its wide-spread distribution, would have allowed for many interesting variations over the millennia, both in the wild and in captivity. We can see from the rapid advances in hybrid flower breeding within the genus has turned up tons of interesting genetic variations, all arising from the same species materials that we still have available to us. Those species then must contain a complex mix of genotype that is not being expressed in their phenotypes. The species are repositories of genes that are either blocked within their species or are heterozygous features that need to be brought to homozygosity in later breeding and selection that only we can apply in domestic garden settings.
The domestic lines that have risen from the species within the last 100 years or so are an amazing collection of art and selection, showing the vast range of genetics found within the genus. Soon we will look at the species themselves.