Erythranthe

Erythranthe, the monkey-flowers and musk-flowers, is a diverse plant genus with at least 111 members (as of 2017) in the family Phrymaceae. "Erythranthe" was originally described as a separate genus, then generally regarded as a section within the genus "Mimulus", and recently returned to generic rank. "Mimulus" sect. "Diplacus" was segregated from "Mimulus" as a separate genus at the same time. "Mimulus" remains as a small genus of eastern North America and the Southern Hemisphere. Molecular data show "Erythranthe" and "Diplacus" to be distinct evolutionary lines that are distinct from "Mimulus" as strictly defined, although this nomenclature is controverisal.
Member species are usually annuals or herbaceous perennials. Flowers are red, pink, or yellow, often in various combinations. A large number of the "Erythranthe" species grow in moist to wet soils with some growing even in shallow water. They are not very drought resistant, but many of the species now classified as "Diplacus" are. Species are found at elevations from oceanside to high mountains as well as a wide variety of climates, though most prefer wet areas such as riverbanks.
The largest concentration of species is in western North America, but species are found elsewhere in the United States and Canada, as well as from Mexico to Chile and eastern Asia. Pollination is mostly by either bees or hummingbirds. Member species are widely cultivated and are subject to several pests and diseases. Several species are listed as threatened by the International Union for Conservation of Nature.
Description.
"Erythranthe" is a highly diverse genus with the characteristics unifying the various species being axile placentation and long pedicels. Other characteristics of species can vary widely, especially between the sections, and even within some sections. Some species of "Erythranthe" are annuals and some are perennials. Flowers are red, pink, purple, or yellow, often in various combinations and shades of those colors. Some species produce copious amounts of aromatic compounds, giving them a musky odor (hence "musk-flowers"). "Erythranthe" is used as food by the larvae of some Lepidoptera species, such as the mouse moth ("Amphipyra tragopoginis"), as a main part of their diet.
Within the section "Erythranthe", stems and leaves range from glabrous to hirsute, and are generally glandular. Leaves can be oblong, elliptical, or oval, with small tooths. Fruiting pedicels are longer than calyces. Calyces have sharp, definite angles and flat sides. Corollas are deciduous, relatively large (tube-throat long), and strongly red to purplish, magentarose, pink, or white, rarely yellow.
"Erythranthe guttata" is the most widespread of the genus "Erythranthe" and its characteristics are fairly representative of the genus. "E. guttata" is tall with disproportionately large long, tubular flowers. Leaves are opposite and oval, long. The species as strictly defined is perennial and spreads with stolons or rhizomes. The stem may be erect or recumbent. In the latter form, roots may develop at lower leaf nodes. Sometimes dwarfed, it may be hairless or have some hairs. Leaves are opposite, round to oval, usually coarsely and irregularly toothed or lobed. The bright yellow flowers are born on a raceme, most often with five or more flowers. The calyx has five lobes that are much shorter than the flower. Each flower has bilateral symmetry and has two lips. The upper lip usually has two lobes; the lower, three. The lower lip may have one large to many small red to reddish brown spots. The opening to the flower is hairy. The fruit is a two-valved capsule long, containing many seeds.
"Erythranthe alsinoides" is similar to several species found in the Pacific Northwest. It is an annual herb that blooms from April–June with a preference for shady and moist dense habitats. The plant is hairy to slightly hairy and grows from tall. The stems are often reddish. The leaves are opposite and have a few prominent upper veins. Blades are long. The petiole is about the same length. The flowers are yellow with reddish-brown spots, usually on the lower lip, and the upper and lower lips have fused, growing . Each flower is attached by a pedicel. The fruits are capsules.
Etymology and taxonomy.
The derivation of "Erythranthe" is from Greek ἐρυθρός (""erythros"), red, with ἄνθος ("anthos""), flower. They are called monkey-flowers because some species have flowers shaped like a monkey's face. The widely used generic name, Latin "mimus" meaning "mimic actor", from the Greek "mimos" meaning "imitator" also alludes to the fancied monkey resemblance. The stem of "Erythranthe" can be either smooth or hairy, and this is known in a few species to be a trait determined by a simple allelic difference. At least "E. lewisii" is known to possess "flypaper-type" traps and is apparently protocarnivorous, supplementing its nutrients with small insects. Variations in color largely reflect concentrations of anthocyanins. The species that are subshrubs with woody stems were originally placed in the section "Diplacus", and this was subsequently made a separate genus. "Diplacus" is clearly derived from within "Mimulus," broadly defined, and was not usually considered to be a separate genus.
The French botanist Édouard Spach established "Erythranthe" as a separate genus with just the type species "Erythranthe cardinalis". In 1885, American botanist Edward Lee Greene classified "Erythranthe" as a section of "Mimulus" while adding "E. lewisii" and "E. parishii". In the 2012 restructuring of "Mimulus" by Barker "et al"., based largely upon DNA evidence, seven species were left in "Mimulus" as strictly defined; "Erythranthe" was greatly enlarged to include 111 species, based upon axile placentation and long pedicels, 46 placed into "Diplacus" (species with parietal placentation and sessile flowers), two placed in "Uvedalia", and one each placed in "Elacholoma", "Mimetanthe", and "Thyridia". All of the American genera are still referred to as "monkey-flowers".
Views on the evolutionary position of the monkey-flower species have changed. It was long considered to be in the family Scrophulariaceae, but is now placed in Phyrmaceae, primarily on the basis of DNA evidence. The genus "Phryma" (comprising only a single species), for which the family is named, is considerably different in morphology from all of the monkey-flowers.
Attempts at crossing species, whether from different sections or within the same section, of "Erythranthe" are not always successful. "E. peregrina" is an example of a successful naturally occurring hybrid that not only arose independently in two different locations, but is also a rare example of evolutionary recent allopolyploidization, complete chromosomal inheritance.
Charles Darwin's 1876 study of inbreeding depression and self-fertility in South American species was a progenitor for the study of "Erythranthe" biology. The genus has become a model system "for studies of evolutionary and ecological functional genomics ... [as it] ... contains a wide array of phenotypic, ecological and genomic diversity." Species under intense genomic study are mostly among the section "Simiolus" ("E. guttata" and relatives) and the section "Erythranthe" (including "E. lewisii", "E. cardinalis", "E. parishii", and others). The genome sequence of "E. guttata" was released in late spring, 2007.
Many issues remain in "Erythranthe" taxonomy. "E. guttata" is highly complex, with many variations apparently reflecting differences in geographic environment and elevation. Molecular geneticists regard the species broadly as including both perennial and annual populations, but there is rationale for treating this complex as several distinct species (perennials are "E. guttata", "E. grandis", and "E. corallina"; annuals are "E. microphylla" and others). The perennials and annuals differ as groups from each other by an inversion sequence on chromosome 8. Evidence tentatively indicates that the perennials evolved from annual ancestors, although some evidence has been interpreted to indicate that "E. nasuta" evolved from "E. guttata" in central California between 500,000 and 200,000 years ago and since then become primarily a self-pollinator. Relationships among the apparently closely related "E. tilingii", "E. minor", and "E. caespitosa" are not clearly understood. Some currently recognized species may be just variants of other species: "E. arenicola", "E. brachystylis", "E. regni". Chromosomal issues may affect the classification of some species: "E. corallina", "E. guttata", "E. nasuta", "E. tilingii", and "E. utahensis".
Reproductive biology.
Before recognition of "E. cinnabarina" as a species, "E. lewisii" was interpreted to be the sister of "E. cardinalis". It is now clear that "E. cinnabarina" and "E. cardinalis" are sister species and that "E. lewisii" and "E. erubescens" are sister species. In the hypothesized phylogeny, the 'cinnabarina/cardinalis' pair is sister to the 'lewisii/erubescens' pair.
"Erythranthe lewisii" is a model system for studying pollinator-based reproductive isolation. "E. lewisii" is pollinated by bees, primarily "Bombus" and "Osmia", which feed on its nectar and transfer its pollen. Although it is fully interfertile with its sister species "E. cardinalis", the two do not interbreed in the wild, a difference ascribed primarily to pollinator differences; "E. cardinalis" is pollinated by hummingbirds, especially "Calypte anna" and "Selasphorus rufus". It was previously reported that evidence strongly linking pollination preference to color differences between the species, but this has been disproven. "E. erubescens" is mostly pollinated by "Bombus balteatus", "B. centralis", "B. flavifrons", and "B. vosnesenskii".
"Erythranthe parishii" is also closely related to "E. lewisii", but it has evolved in a different direction as a self-pollinated species with small flowers.
"E. eastwoodiae", "E. nelsonii", "E. rupestris", and "E. verbenacea" are also pollinated by hummingbirds. These four species as well as "E. cardinalis" and "E. nelsonii" produce bisexual flowers and are self-compatible. This approximate ratio of insect vs hummingbird pollination holds true for the rest of the genus. There have been two separate transformations to hummingbird pollination. Pollination changes are highly affected by changes in flower morphology. "E. cardinalis" and its sister species "E. cinnabarina" likely evolved via allopatric speciation.
"Erythranthe guttata" is pollinated by bees, such as "Bombus impatiens". Inbreeding reduces flower quantity and size and pollen quality and quantity. "E. guttata" also displays a high degree of self-pollination. "Erythranthe nasuta" evolved from "E. guttata" in central California between 200,000 and 500,000 years ago and since then has become primarily a self-pollinator.
Distribution and habitat.
Over 80% of "Erythranthe" species are found in western North America, especially California, Oregon, and Washington. Genus members are also found in Baja California, Alaska, British Columbia, Nevada, Utah, Idaho, Montana, Wyoming, Colorado, Arizona, New Mexico, and to a lesser extent the midwestern states, northeastern states, Canada, and Latin America. Members of this genus are found in eastern Asia; several species of which have a high degree of similarity with some of the species found in North and South America.
A large number of the species grow in moist to wet soils with some growing even in shallow water. They are not very drought resistant, but the species now classified as "Diplacus" are. Some species grow in dry areas, others in wet habitats, such as members of the section "Simiolus", which are hydrophilic. Both overall plant size and corolla size vary greatly throughout the genus. A minimum of 25 of the species are listed as threatened by the International Union for Conservation of Nature. Species are found at elevations from oceanside to high mountains as well as a wide variety of climates, though most prefer wet areas such as riverbanks.
Pests and diseases.
"Diplacus", "Erythranthe", and "Mimulus" are subject to a very similar set of pests and diseases. The pests these genera are susceptible to include: gall midges, golden mealybugs, thrips, and seed bugs. Diseases they are susceptible to include: crown gall, aster yellows phytoplasma, impatiens necrotic spot virus (INSV), leaf spots, powdery mildew — especially "Erysiphe brunneopunctata" and 
"Erysiphe cichoracearum", botrytis blight, pythium root rot, rusts, cucumber mosaic virus (CMV), as well as mineral and nutrient deficiencies.
Human culture.
Horticulture.
In horticulture, several species, cultivars and hybrids are used. Because of their wide range and many variations, the most important are those derived from "E. gutatta" and "E. lutea". "E. cuprea" alone has at least 10 cultivars and hybrids.
Culinary uses.
"Erythranthe" species tend to concentrate sodium chloride and other salts absorbed from the soils in which they grow in their leaves and stem tissues. Native Americans and early travelers in the American West used this plant as a salt substitute to season wild game. The entire plant is edible, but reported to be very salty and bitter unless well cooked. The juice from the leaves was used as a poultice for mild skin irritations and burns. Leaves can be used in salads and soups; flowers taste best before blooming. "E. lutea" has been used for cooking in Peru.
Alternative medical use.
"Erythranthe" has been listed as one of the 38 plants that are used to prepare Bach flower remedies, a kind of alternative medicine promoted for its effect on health. However, according to Cancer Research UK, "there is no scientific evidence to prove that flower remedies can control, cure or prevent any type of disease, including cancer".
Species.
Species alphabetically.
This is a listing of "Erythranthe" per Tropicos in February 2017, unless listed as "newly discovered":
Species sectionally.
 
In a 2014 paper, G. L. Nesom and N. S. Fraga placed "Erythranthe" members into the following 12 sections, unless listed as "newly discovered":