Aquilegia

Etymology

The 1st-century AD Greek writer Dioscorides called columbines Isopyrum, a name used presently applied to another genus, Isopyrum. In the 12th century, the abbess and polymath Hildegard of Bingen referred to the plants as agleya from which the genus's name in German, Akelei, derives. The first use of aquilegia with regards to columbines was in the 13th century by Albertus Magnus. In the 15th and 16th centuries, the names Colombina, Aquilina, and Aquileia came into use. With the Swedish biologist Carl Linnaeus's 1753 Species Plantarum, the formal name for the genus became Aquilegia, though limited use of Aquilina persisted in scientific usage until at least 1901.

Several scientific and common names for the genus Aquilegia derive from its appearance. Another possible etymology for Aquilegia is a derivation from the Latin aquam legere ("to collect water"), The most common English-language name, columbine, likely originates in the dove-like appearance of the sepals (columba being Latin for dove).

There are a number of other common names for Aquilegia across different languages. In English, these include granny's bonnet for some plants in the species Aquilegia vulgaris. In French, the word ancolie is the common name for Aquilegia, while individual members of the genus have been called gants-de-Notre-Dame ("Our Lady's glove"). In Italian, amor-nascoto ("love-born") has been used.

Description

Aquilegia is a genus of herbaceous, perennial flowering plants in the family Ranunculaceae (buttercups). The genus is highly variable in appearance. Though they are perennials, certain species are short-lived, with some exhibiting lifespans more similar to biennials and others only flourishing for six to eight years. Following a dormant period in the winter, columbines will grow foliage and have a brief flowering period. Later, seed heads will emerge and split, sowing new seed. The foliage lives through the summer before wilting and dying going into the fall.

Aquilegia plants grow from slim, woody rootstocks that comprise the perennial portion of the plants. One or more annual aerial stems rise from the rootstocks each growing season, ultimately drying out following fruiting. Leaves can grow in both basal (from the base of the plant) and cauline (from the aerial stem) arrangements. Leaves emanating from closer to the plant's core are generally borne on flexible petioles, while leaves further from the core generally lack petioles. The compound leaves of Aquilegia are generally ternate (each leaf dividing in three leaflets), biternate (each leaf dividing into three components that in turn each bear three leaflets, for a total of nine leaflets), or triternate (each leaf divides into three components three times, for a total of 27 leaflets).

The flowering stems emerge from rosettes during the spring and summer. Each inflorescence appears at the terminus of an aerial stem and can reach 30 cm long. Depending on the species, an inflorescence will feature one to ten of either cymes (flower clusters) or solitary flowers. Flower morphology varies across the genus, but all columbine flowers emerge from buds that are initially nodding. Flowers can be monochromatic or display multiple colors. The typical flower color for columbines is blue in shades ranging into purple and nearly black shades. Blue flowering is especially the norm in European columbines, where only A. aurea possesses yellow flowers. In North America, yellow and red flowers are typical, with blue and blue-purple flowers almost exclusive to high-altitude species.

The perianth (non-reproductive portion) of Aquilegia flowers generally comprise five sepals that look like petals and five petals. Depending on the species, spurs can have a hooked, horn-like appearance, with straight to coiled spurs also present in the genus. Some columbines, such as A. ecalcarata, are naturally spurless. Recessive spurlessness individuals and populations can also be found within typically spurred species.

The reproductive portions of columbine flowers comprise the stamen (male) and gynoecium (female). The stamina, which bear the anthers from which pollen emerges, form whorls of five around the gynoecia. The total number of stamen varies between species. There are generally scale-shaped staminodes between the stamen and female pistil structures. The flowers undergo three stages of anthesis: a premale stage, where the flower perianth is open but the anthers are not dehisced (split to expose pollen); the male stage where with the perianth present and the anthers dehiscenced, and a postmale stage where the anthers have withered but the perianth remains.

Aquilegia are bisexual (featuring both male and female organs) and capable of self-pollination, through either or both autogamy (does not require assistance from pollinators) and geitonogamy (requires pollinators). A. formosa and A. eximia may exhibit adichogamy, where male and female organs do not operate simultaneously to prevent self-fertilization. Fertilization via cross pollination also occurs in Aquilegia, with pollinators carrying pollen from one flower to the stigma of another.

Aquilegia fruit are follicles. These follicles have a split on one side and terminate with a curling tip known as a beak. Seed germination is primarily dependent on temperature, with seeds typically requiring a multi-month period of summer temperatures followed by a multi-week to multi-month exposure to winter temperatures (vernalization) prior to germinating once temperatures warm with the arrival of spring. This prevents seedlings from emerging until there are survivable environmental conditions.

The chromosome number for columbines is 2n=14. Individual plants have been recorded with other anomalous chromosome numbers, ranging up to 2n=32. It is possible that B chromosomes impact the phenotype and the fertility of individual plants that possess them.

Phytochemistry

Among Aquilegia that are cyanophores (organisms that produces a blue color) like A. vulgaris, the cyanogenic glycosides compounds dhurrin and triglochinin have been observed. Cyanogenic glycosides generally taste bitter and can be toxic to animals and humans. Ingestion of 20 g of fresh A. vulgaris leaves by a human was observed as causing convulsions, respiratory distress, and heart failure. A child who consumed 12 A. vulgaris flowers experienced weakness of the limbs, cyanosis, drowsiness, and miosis; all symptoms abated after three hours. Mature seeds and roots contain toxins that, if consumed, are perilous to human heart health.

The presence of the antibacterial flavonoid compound isocytisoside has been observed in A. vulgaris. Polyphenols, primarily flavonoids, are the main component of hydroethanolic extract from A. oxysepala. These compounds function as antioxidants. A study of A. oxysepala extract found it has a good scavenging effect on DPPH, superoxide anion, and hydroxyl radicals, but a poor scavenging capacity towards hydrogen peroxide. For all these, ascorbic acid has a superior scavenging effect to the extract.

In flowering plants, the presence of phenylpropanoids can serve as protection from ultraviolet (UV) light and as a signaling mechanism towards pollinators. A study that examined A. formosa flowers determined that the petals and sepals had uniform levels of UV-resistant phenylpropanoids.

Ecology

Despite its toxicity and in the absence of incentives,

In the Northeastern United States and Eastern Canada, A. canadensis serves as the host plant for the butterfly Erynnis lucilius (columbine duskywing). In two periods, the first from April to June and the second from July to September, the butterflies lay their eggs on the underside of the columbine leaves. The latterly laid brood overwinters as caterpillars in the plant litter around the columbine. In the Western United States, Bombus occidentalis (western bumblebee) has been observed nectar robbing from A. coerulea by opening or using holes cut in the spurs.

Also in North America, three leaf miner species in the genus Phytomyza lay their eggs on Aquilegia: P. aquilegiana in the east, P. aquilegivora in the Midwestern United States, and P. columbinae in the west. Collectively known as the columbine leaf miners, white trails or splotches on leaves indicate where the larvae consumed the tissue between the leaves' surfaces. The larvae will cut through the leaves, pupating in small puparium on the leaves' undersides. Adults pierce the leaves with their ovipositors to access liquids in the plants, leaving marks. Another Phytomyza columbine leaf miner, P. ancholiae, is native to France.

Originally from Europe, Pristiphora rufipes (columbine sawfly) is now also found in Canada and the United States. After developing from eggs laid on columbine leaves in late spring, the green larvae will eat the leaves from the outside in during their active period from April to June. In cases where many larvae are on the same plant, only the stem and flowers may go uneaten. The larvae mature within a few weeks, after which they drop from the plants and pupate in cocoons.

Several fungi attack columbine foliage, including Ascochyta aquilegiae, Cercospora aquilegiae, and Septoria aquilegiae.

Pollination

Following the evolution of the genus, Aquilegia developed diverse floral features including varied orientation, coloration, and nectar spur morphology to attract different pollinators, contributing to speciation.

Eurasian columbines are primarily pollinated by flies, bees, and bumblebees. North American columbines are generally pollinated by bees, bumblebees, hawkmoths, and hummingbirds. Pollination by hummingbirds is more typical to red-flowered North American Aquilegia, while pale-flowered columbines may have developed to increase their visibility to hawkmoths in twilight.

Nectar spur length on particular columbines is often correlated to their associated pollinators. While nectar spur length in Eurasia varies little, there is substantial variation in North American spur length. While hawkmoths are present in Eurasia, there are not Eurasian columbines with the hawkmoth pollination syndrome which includes longer spurs. In North America, the presence of hummingbirds which are absent in Eurasia and possess tongue lengths that are generally intermediate between other pollinators and hawkmoths may have functioned as a stepping stone that allowed North American Aquilegia to evolve the hawkmoth pollination syndrome.

While a given population of Aquilegia may settle a particular habitat and develop pollination syndromes for certain pollinators, this does not necessarily translate into ecological speciation with genetic barriers between species. The likelihood of such speciation increases when floral mutations and pollinator behavioral changes coincide with isolated, small populations, as in the case of A. micrantha var. mancosana.

Taxonomy

Within Linnaean taxonomy, Aquilegia was first described as a genus in Carl Linnaeus's 1753 Species Plantarum. Another historic assignment, made by the Swedish botanist in 1870, placed Aquilegia as the sole member of the family Aquilegiaceae.

Columbines are most commonly assigned to the tribe Isopyreae, though they are sometimes placed within Aquilegieae. The placement of the tribe containing Aquilegia has been uncertain, with alternating assignments to two subfamilies: Thalictroideae and Isopyroideae. Regardless of the placement, Aquilegia forms a basal, paraphyletic group with the genera Isopyrum and Thalictrum (meadow-rues) which is characterized by their plesiomorphy (characteristics shared between clades from their last common ancestor) with Berberidaceae.

The broadly accepted circumscription of Aquilegia was established by the American botanist Philip A. Munz in his 1946 monograph Aquilegia: The Cultivated and Wild Columbines. The only element of Munz's circumscription which has been substantially contended is his inclusion of the spurless Asian species A. ecalcarata, which is sometimes instead segregated into the closely related genus of spurless-flowered Semiaquilegia; Semiaquilegia ecalcarata remains the species's common name in cultivation. Another spurless columbine, A. micrantha var. mancosana, was also once reassigned to Semiaquilegia. Reassignments to Isopyrum and Paraquilegia, such as P. anemonoides in 1920, have been more permanent.

Evolution

There are no good fossils of columbines and other Thalictroideae that indicate how they evolved and radiated. Genetic evidence suggests that the last common ancestor among Thalictroideae lived in East Asia approximately 36 million years ago, during the late Eocene.

A 2018 study of genetic evidence indicated that Aquilegia first appeared during the Upper Miocene approximately 6.9 million years ago. The genus split into two clades 4.8 million years ago, with one clade eventually populating North America and the other radiating across Eurasia. A 2024 study found that the divergence between Urophysa, Semiaquilegia, and Aquilegia instead occurred over a relatively short 1 million-year-long period approximately 8 to 9 million years ago. The species is thought to have originated in the mountainous portions of south-central Siberia.

Studies of Aquilegia genetics indicated that North American Aquilegia species shared their last common ancestor with species from the Asian Far East between 3.84 and 2.99 million years ago. This analysis corresponded with the theory that Aquilegia reached North America via a land bridge over the Bering Strait. While there were several periods after this date range where the Beringian land bridge connected Asia and North America, these occurred when climatic conditions would have prevented Aquilegia migration through the region.

Genetic information suggests that the diversification rates of columbines rapidly increased about 3 million years ago,

Among Asian and European columbines, differences in floral morphology and pollinators are lower between species than between North American species. However, there are approximately the same number of Aquilegia species across the three continents. This suggests that pollinator specialization played a dominant role in North American columbine speciation while habitat specialization was the primary driver of Asian and European columbine speciation.

The nectar spurs present in Aquilegia are an unusual evolutionary trait, arising on the ancestor of all Aquilegia up to approximately 7 million years ago. as responsible for cell proliferation during the early stage of spur development. POP, which encodes a C2H2 zinc-finger transcription factor, appeared at higher levels in the petals of the spurred Aquilegia studied than in A. ecalcarata.

Current species

Main article: List of Aquilegia species

According to different taxonomic authorities, the genus Aquilegia comprises between 70 and over 400 taxa. Some totals correspond more closely with Munz's 1946 total of 67, while online Tropicos and the International Plant Names Index have accepted over 200 and 500, respectively. , the Royal Botanic Gardens, Kew's Plants of the World Online accepts 130 species.

The American botanist and gardener Robert Nold attributed the substantial total of named species, subspecies, and varieties to the 19th-century practice of assigning names to even minutely distinct specimens. However, Nold also held that overly broad species could increase the number of varietal names. The Italian botanist Enio Nardi stated that authors assessing Aquilegia as containing fewer than 100 species "either mask or underestimate their splitting into subspecies, many of which were originally described at the species level" and remain accepted as species in taxonomic indices.

The type species of the genus is A. vulgaris, a European columbine with high levels of physical variability. Most European Aquilegia are morphologically similar to A. vulgaris, sometimes to the point where visually discerning them from A. vulgaris is difficult. A. vulgaris is sometimes considered to encompass Iberian and North African columbines that are not accepted as separate species for reasons that Nardi said were founded in "tradition, more cultural than scientific".

Natural hybridization

A lack of genetic and physiological barriers permits columbine hybridization across even distantly related species with high degrees of morphological and ecological differences.

While artificial pollination has determined the extent of the genus's interfertility, breeding between plants within the same species is generally more common even in settings both natural and cultivated where multiple columbine species are present. A significant barrier to hybridization occurring naturally is the proclivity of pollinators to preferentially support infraspecific crossbreeding due to the pollinators' recognition of familiar flower typology.

In North America, species with flowers adapted to hummingbird and hawkmoth pollination have far reduced natural hybridization with species that do not share these adaptations.

In China, clades distinguishing eastern and western A. ecalcarata populations indicate gene flow from different species. A study using genetic modeling indicated that the spurless A. ecalcarata may have developed from two separate mutations from discrete eastern and western populations of the spurred A. kubanica, an instance of a hybrid parallel evolution.

Distribution

Aquilegia species have natural ranges which span the Northern Hemisphere in Eurasia and North America.

A. vulgaris, a European columbine which possibly originated in the Balkans, These introduced A. vulgaris populations typically originated from ornamental cultivation.

Some columbines are narrowly endemic, with highly restricted ranges. A. paui only has a single population with four subpopulations within a few kilometers of each other in the Ports de Tortosa-Beseit mountains of Catalonia. , the entire population of A. nuragica estimated as 10 to 15 individuals populated an area of approximately 50 m2 on Sardinia.

Conservation

Certain Aquilegia have been identified as having elevated risks of extinction, with some appearing on the IUCN Red List. Two Sardinian columbines, A. barbaricina and A. nuragica, have conservation statuses assessed by the IUCN as critically endangered and the same organization listed the species in their 2005 Top 50 Mediterranean Island Plants campaign for conservation. Some columbines, including both rare and common taxa, are subject to governmental regulations. The conflation of taxa has sometimes resulted in uncertainty regarding their conservation statuses.

Humans pose a significant threat of impairing columbine population health and driving extinction. Beyond the desirability of the flowers for display, uncommon or rare Aquilegia face the risk of destruction by botanists and others seeking to add them to their herbariums or private collections.

Cultivation

In Europe, cultivation of columbines may have begun over 1,700 years ago. Archaeobotanical evidence suggests that A. vulgaris was cultivated for ornamental purposes in 3rd-century AD Roman Britain. Finds of columbines at a late Saxon site near Winchester Cathedral and three later medieval German sites have also been interpreted as using the plant for gardening. In 12th-century Italy, people may have supported A. vulgaris or A. atrata populations near religious structures, possibly due to the contemporary treatment of columbines as Christian symbols.

Aquilegia are grown for a variety of purposes. Cut flowers can be collected once the flower opens. The dried fruit can also be used in ornamental arrangements. Columbines function well in garden borders and can occupy shade and cottage gardens. Certain columbines are suited for well-drained rock gardens or alpine gardens. A few, such as the dwarf woodland plant A. flabellata var. pumila, favor moist shaded plantings.

Lifespans for cultivated columbines are generally relatively short for perennials, with a plant's peak typically occurring in its second year. Two- to three-year-long lives are typical in cultivated A. coerulea and A. glandulosa, In gardens, columbines will generally live three to four years. This lifespan can be extended by deadheading, where dead flowers are removed prior to the plant expending the energy needed to produce fruit.

In cultivation, the seasonal cycle that releases columbine seeds from dormancy can be replicated via a stratification where seeds are exposed to two to four weeks of cool temperatures prior to sowing.

If permitted, cultivated columbines drop numerous seeds around themselves, resulting in a rapid proliferation of seedlings. These seedlings can give the impression that short-lived plants are living longer. If identical plants are desired, basal cuttings can be performed in early summer.

Several animals are considered pests of cultivated columbines. Columbine leaf miners of the Phytomyza genus leave white patches or paths on leaves, but the damage is only cosmetic and does not generally require chemical pesticides. The moths Papaipema lysimachiae and P. nebris (stalk borer) both adversely affect columbines; scraping the ground around impacted plants can destroy the moths' seeds. The larval stage of the Erynnis lucilius (columbine duskywing) is known as the columbine skipper, and the larvae can chew leaves and bind them together with silk. Aphid infestation is another frequent issue, requiring rapid intervention to prevent significant destruction.

Cultivars and cultivated hybrids

Columbine cultivars are popular among gardeners, particularly in the Northern Hemisphere. received the Royal Horticultural Society's Award of Garden Merit.

Double-flowered columbines were developed from A. vulgaris and can be classified into three types. The Flore Pleno group, described in the English herbalist John Gerard's 1597 book Herball, possesses plants where the flowers are elongated and the petals are rounded. The Veraeneana group come in several colors of flower and possess marbled green and gold foliage. The Stellata group, described in the English botanist John Parkinson's 1629 book Paradisi in Sole Paradisus Terrestris, has flowers which are star-shaped and have pointed petals. The three-colored, double-flowered cultivar 'Nora Barlow' first discovered by the botanist and geneticist Nora Barlow is sometimes classified as part of the Stellata group, but displays a greater quantity of particularly narrow sepals than other members of that group.

Experimental hybridization attempts have determined that the degree of interfertility of columbines is not identical across the genus. While North American columbines easily hybridize with each other and most Eurasian Aquilegia, the Asian species A. oxysepala and A. viridiflora resist hybridization with North American columbines. Hybrids with A. vulgaris as one parent frequently look closer to A. vulgaris than any other parent. Many older garden columbines that are suspected hybrids resemble A. vulgaris, making true parentage difficult to determine. The American gardener Robert Nold said that "more has been written about 'Hensol Harebell' a hybrid of [A. alpina and A. vulgaris which originated in early 20th-century Scotland] than perhaps any other interspecific hybrid", noting its greater affinity to A. vulgaris in appearance.

More recent garden hybridization work has primarily utilized North American columbines for their varied greater flower sizes and variety of colors. While columbine flowers often face downwards in a nodding arrangement, hybridizers have introduced the A. coerulea trait of upward-facing flowers. The first such hybrids were the McKana Group (also known as McKana's Giants) which won the 1935 All-America Selections bronze medal for new seed offerings and Mrs. Scott-Elliot hybrids. However, these large-flowered columbines produced unpredictably colored flowers. Newer F1 hybrids series have larger blooms with greater uniformity in color.

Human uses

Medicinal and herbal

Asian traditional medicine practitioners, Indigenous North Americans, and Medieval Europeans have considered columbines plants medicinal herbs. Modern scientific research has determined that columbines can possess antioxidant, antibacterial, and anti-cancer qualities.

In China, A. oxysepala has been used as a dietary supplement and medicine for thousands of years. A. oxysepala has been used there to treat diseases in women such as irregular menstruation and intermenstrual bleeding. While its extract's function as an antioxidant is known, with its medicinal use possibly attributable to the extract's good scavenging of superoxide anion radicals, it is inferior to the common dietary supplement ascorbic acid. Research has also determined A. oxysepala to possess antibacterial qualities.

A. sibirica has been a significant part of Asian traditional medicine, including traditional Mongolian medicine, and the plant has been used to treat diseases in women, asthma, rheumatism, and cardiovascular diseases. It was also known to inhibit Staphylococcus aureus, one of the bacteria responsible for staphylococcal infections. A. sibirica also possesses antifungal qualities. Extracts showed the presence of chlorogenic acid and caffeic acid.

Some Indigenous North American peoples used the roots of columbines to treat ulcers.

Other uses

Prior to deaths due to overdoses, small quantities of flowers from several columbines species were considered safe for human consumption and were regularly eaten as colorful garnishes and parts of salads. Several Indigenous North American peoples have been described as eating A. formosa: the Miwok may have boiled and eaten them with early spring greens, while Hanaksiala and Chehalis children may have sucked nectar from the flowers. Columbine flowers are described as sweet,

The American botanist Verne Grant repeatedly utilized Aquilegia in research published between the 1950s and the 1990s to explain the role that hybridization, polyploidy, and other processes played in how plant evolution and speciation occur. Among Grant's works that utilized Aquilegia to illustrate evolutionary patterns and processes was his influential 1971 book Plant Speciation. The five species groups that Grant proposed in 1952 remains a foundational element for a phylogenetic understanding of columbines.

In 21st-century scientific research of plant development, ecology, and evolution, Aquilegia has been considered a model system.

In culture

European columbines have been assigned several meanings since the ancient period. Within art, A. vulgaris has been a symbol of both moral and immoral behaviors, as well as an ornamental motif. In ancient Greece and ancient Rome, the spurs of columbines were interpreted as phallic and the plants were associated with the fertility goddesses Aphrodite and Venus. where the species is symbolic of deception and serves as an omen of death.

Medieval European artists associated the columbines with Christian sacredness and sublimity, with Flemish painters of the 15th century frequently depicting them in prominent locations within their Christian artworks. In The Garden of Earthly Delights (1503–1504) by Hieronymus Bosch, A. vulgaris serves as a symbol for bodily pleasures. Portrait of a Princess (1435–1449) by Pisanello depicts multiple A. atrata at different angles as part of the floral ornamentation that makes that painting characteristic of the international Gothic style.

Columbines have several meanings in the language of flowers, a manner of communicating using floral displays. In the 1867 English book The Illustrated Language of Flowers by a "Mrs. L. Burke", columbines are generally described as communicating "folly". The same book identifies purple columbines with "resolve to win" and red columbines with "anxious and trembling". Columbines, due to their resemblance to doves, have been associated with the Holy Spirit in Christianity since at least the 15th century.

A. coerulea is the state flower of Colorado. The Colorado General Assembly passed legislation in 1925 making it illegal to uproot A. coerulea on public lands. The law also limits on how many buds, blossoms, and stems may be picked from the species by a person on public lands. The name of the town of Columbine Valley, Colorado, ultimately derives from the state flower. Colorado's A. coerula also served as the inspiration for one of the state's official songs, "Where the Columbines Grow", written in 1909. It was used in the heraldry of the former city of Scarborough in the Canadian province of Ontario.

The asteroid 1063 Aquilegia was named for the genus by the German astronomer Karl Reinmuth. He submitted a list of 66 newly named asteroids in the early 1930s, including a sequence of 28 asteroids that were all named after plants, in particular flowering plants.

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