Adiantum viridimontanum
Encyclopedia
Green Mountain maidenhair fern (Adiantum viridimontanum) is a rare fern
limited to outcrops of serpentine rock in New England
and Canada. A hybrid between Adiantum pedatum
(northern maidenhair fern) and Adiantum aleuticum
(western maidenhair fern), it closely resembles its parent species. In all three, the leaf blade is cut into finger-like segments, themselves once-divided, which are borne on the outer side of a curved, dark, glossy stalk (the rachis
). The "fingers" may be drooping or erect, depending on whether the individual fern grows in shade or sunlight. Spores are borne under rolled flaps of tissue (false indusia) at the edge of the ultimate blade segments, a characteristic unique to the genus Adiantum. A. viridimontanum is difficult to distinguish from its parent species in the field. It can generally be separated from A. pedatum by the shape of the ultimate segments and by its habitat on thin, exposed serpentine soil
s rather than in rich woodlands. It more closely resembles A. aleuticum than A. pedatum; however, the stalks of the ultimate segments and the false indusia are longer, and the spores larger, in A. viridimontanum when compared to A. aleuticum.
Until 1991, the Green Mountain maidenhair fern was grouped with the western maidenhair fern, which grows both in western North America and as a disjunct
on serpentine outcrops in eastern North America. At one time, western maidenhair fern was classified as a variety (A. pedatum var. aleuticum) of the northern maidenhair fern. However, after several years of study, the botanist Cathy Paris recognized that the western maidenhair constituted a separate species, and that some of the specimens that had been attributed to that taxon were a third, hybrid species. She named the new species A. viridimontanum for the site of its discovery in the Green Mountains
in Vermont
. It has since been located in Quebec
and in one site on serpentine in coastal Maine
.
Due to its limited distribution and similarity to other Adiantum species within its range, little is known of its ecology. It thrives on sunny, disturbed areas where ultramafic rock is covered with thin soil, such as road cuts, talus
slopes, and asbestos
mines. Individual plants seem long-lived, and new individuals only infrequently reach maturity. It is one of four species endemic to serpentine in eastern North America and is considered globally threatened due to its habitat restrictions.
fern. Its fronds range from 30 to 75 cm (11.8 to 29.5 in) in size. The rachis appears to fork into two outward- and backward-curving branches, which bear the penultimate segments of the leaf along the outer side of the curve. These are pinnately divided into the ultimate segments. While this structure is sometimes called pedate
, it is more accurately described as pseudopedate
; the basal pinnae of the central penultimate segment are greatly enlarged and are further divided and subdivided to form the penultimate segments on either side.
The rhizome
shows little branching, with intervals of 4.0 to 7.5 mm between nodes. It measures 2.0 to 3.5 mm in diameter. The rhizome and the base of the stipe
have bronze
-colored scales. The stipe and rachis range from chestnut brown (castaneous) to dark purple (atropurpureous) in color and are glabrous; the stipe is about 2 to 3 mm in diameter while the rachis is smaller, 1 to 2 mm. The basal pinnae are from three to seven times pinnate (due to the pseudopedate structure of the blade), while the apical part of the blade (and the corresponding segments of the basal pinnae) are once-pinnate. This part of the blade (the apparent "pinna", or penultimate segment) is typically lanceolate in shape. The overall arrangement of the penultimate segments ranges from drooping and fan-shaped (flabellate) on plants growing in the shade to funnel-shaped on plants growing in full sun, in which case they stand stiffly erect.
The ultimate segments of the divided blade are borne on short, dark stalks of 0.6 to 1.5 mm, with the dark color often spreading into the base of each segment. They are long and obliquely triangular, the basiscopic margin forming the hypotenuse
. The tip of the segments is typically acute, but entire (not pointed). They measure from 9.5 to 22.5 mm in length and 4.2 to 7.5 mm in breadth, the average length being about 2.5 times the breadth. Their tissue is firmly leafy (herbaceous) to papery (chartaceous) in texture, and bright green to bluish-green in color. As in other members of Adiantum, the glabrous leaves shed water when young. In shady conditions, the ultimate segments lie within the plane of the blade, but tend to twist out of the plane when grown in the sun. The acroscopic margins of these segments are lobed, with narrow (less than 1.0 mm) incisions lying between lobes. In fertile segments, these lobes are recurved to form false indusia beneath the leaf. These are transversely oblong, from 2 to 5 mm in length and from 0.6 to 1.4 mm in width.
The sori (clusters of spore
-bearing structures) are borne on the underside of the leaf beneath the false indusium. This characteristic is a synapomorphy
for Adiantum: a trait found only in Adiantum and not in its closest relatives. (In fact, the sori under false indusia are not only unique to Adiantum but present in all its members.) The sori are round, and are found on veins ending in the false indusium, below the veins' ends. The spores are tetrahedral to globose, yellow in color, and measure 41 to 58 micrometers (μm) in diameter (averaging 51.4 μm), on average larger than other species in the A. pedatum complex. Spores appear in the summer and fall. The species has a chromosome number of n = 58.
Another distinguishing character is the shape of the medial ultimate segments, which are oblong in A. pedatum and long-triangular or kidney-shaped (reniform) in A. viridimontanum some specimens of A. aleuticum. Furthermore, A. viridimontanum can grow in both shade and sun, while A. pedatum grows in shade only.
Adiantum viridimontanum can be separated from the morphologically similar individuals of A. aleuticum by the greater length of the stalks on the medial ultimate segments and of the false indusia, measuring greater than 0.9 mm and greater than 3.5 mm, respectively, in A. viridimontanum. Spore size is also a useful character ex situ; the average A. viridimontanum spore measures 51.4 μm in diameter. While A. aleuticum spores can reach up to 53 μm, they average about 43 μm. In A. aleuticum growing as a disjunct on eastern serpentine (the most likely specimens to be confused with A. viridimontanum), the rhizome is much more frequently branched, with intervals of 1.0 to 2.0 mm between nodes.
(then classified as Adiantum pedatum var. aleuticum) on the serpentine tableland of Mount Albert
by Merritt Lyndon Fernald
in 1905, botanists began to search for the fern on ultramafic outcrops elsewhere in Quebec
and Vermont
. It was first identified in Vermont by L. Frances Jolley in 1922 at Belvidere Mountain in Eden
. In 1983, William J. Cody referred A. pedatum growing on serpentine, both in eastern and western North America, to A. pedatum ssp. calderi instead. Many of the stations for the fern in Vermont were described in 1985, in a survey of ultramafic outcrops in that state.
From 1983 to 1985, Cathy A. Paris, then a graduate student, gathered specimens of A. pedatum from non-serpentine soils in the Midwest and Vermont, and from serpentine soils in New England and Canada, for biosystematic analysis. In 1988, Paris and Michael D. Windham published a the results of this analysis, revealing A. pedatum in North America to be a cryptic species complex
. They showed that A. pedatum sensu lato included two well-distinguished diploid taxa, one found in the Eastern woodlands, and the other found both in the Western mountains and as a disjunct on serpentine in the East. However, not all of the serpentine disjuncts proved to belong to the Western taxon. Several of them, including most of the specimens in Vermont, were found to be tetraploid, forming a taxon distinguishable from the two diploids. Isozyme
banding patterns suggested that the tetraploid had arisen by hybridization between the eastern subspecies of non-serpentine woodlands and the western and serpentine taxon, followed by a duplication of the hybrid genome. This allotetraploid was also morphologically intermediate between the two taxa, although it more closely resembled the serpentine taxon (hence its earlier referral to var. aleuticum). Paris formally described the tetraploid as a new species, A. viridimontanum, in 1991, and also separated the western and serpentine taxon from A. pedatum as A. aleuticum. The type specimen of A. viridimontanum was collected from a talus slope at the old asbestos
mine on Belvidere Mountain on August 28, 1985. The sequencing of several chloroplast
DNA loci has revealed that the A. viridimontanum chloroplast genome most closely resembles that of A. aleuticum, suggesting that A. aleuticum was the maternal parent of A. viridimontanum.
and Quebec
. Seven stations in Vermont
lie in the Missisquoi Valley
, in the northern Green Mountain
s, giving the fern its name. The ultramafic rocks of this area extend northwards into Quebec, where eight stations are known in southern Quebec and six in the Thetford Mines area. It is also known from one station on serpentine on Deer Isle, Maine
.
The fern thrives in thin serpentine soil
s on sunny, disturbed habitats such as roadcuts and talus
slopes, in dunite
and other ultramafic rocks. Anthropogenic disturbance has removed thicker soils and increased sun exposure in many of these sites; for instance, many of the Quebec stations are in asbestos mines, both abandoned and active. In more natural habitats, frost weathering
and erosion may promote rock fall and maintain suitable habitat.
The eastern serpentine outcrops where Green Mountain maidenhair thrives are largely depauperate of endemics compared to serpentine exposures globally. Green Mountain maidenhair is one of only five taxa (four species and a variety) recognized as strictly endemic to serpentine when they occur in eastern North America.
, typically in bright sunlight on thin serpentine soils. These requirements allow Green Mountain maidenhair to colonize recently disturbed sites on ultramafic outcrops, where bedrock has been exposed and competing plants have been removed. The populations appear stable, with the long life of individuals compensating for low recruitment
rates.
Little is known about the role of Green Mountain maidenhair in the ecosystem. In general, ferns are less susceptible to herbivory than angiosperms due to higher levels of toxic and distasteful compounds in their foliage. The Green Mountain maidenhair is not known to be threatened by a particular predator or disease.
Conservation of Green Mountain maidenhair is primarily limited by its restricted habitat on serpentine cliffs and talus slopes. However, these sites are also of little value to humans. The most likely threat to the species is expansion of asbestos mining, which often occurs near populations of the fern, or other reuse of abandoned asbestos mines. Road construction might also threaten some sites, although this is mitigated by the fern's avidity for disturbed serpentine. None of the sites are as yet known to be invaded by non-native plants.
Fern
A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...
limited to outcrops of serpentine rock in New England
New England
New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...
and Canada. A hybrid between Adiantum pedatum
Adiantum pedatum
Adiantum pedatum is a maidenhair fern native to moist woodland in eastern North America.Adiantum aleuticum was once considered a subspecies...
(northern maidenhair fern) and Adiantum aleuticum
Adiantum aleuticum
Adiantum aleuticum is a species of fern in the genus Adiantum, native mainly to western North America from the Aleutian Islands of Alaska, south to Chihuahua, and also locally in northeastern North America from Newfoundland south to Maryland.The fronds grow to 15-110 cm high, and are...
(western maidenhair fern), it closely resembles its parent species. In all three, the leaf blade is cut into finger-like segments, themselves once-divided, which are borne on the outer side of a curved, dark, glossy stalk (the rachis
Rachis
Rachis is a biological term for a main axis or "shaft".-In zoology:In vertebrates a rachis can refer to the series of articulated vertebrae, which encase the spinal cord. In this case the rachis usually form the supporting axis of the body and is then called the spine or vertebral column...
). The "fingers" may be drooping or erect, depending on whether the individual fern grows in shade or sunlight. Spores are borne under rolled flaps of tissue (false indusia) at the edge of the ultimate blade segments, a characteristic unique to the genus Adiantum. A. viridimontanum is difficult to distinguish from its parent species in the field. It can generally be separated from A. pedatum by the shape of the ultimate segments and by its habitat on thin, exposed serpentine soil
Serpentine soil
A serpentine soil is derived from ultramafic rocks, in particular serpentinite, a rock formed by the hydration and metamorphic transformation of ultramafic rock from the Earth's mantle....
s rather than in rich woodlands. It more closely resembles A. aleuticum than A. pedatum; however, the stalks of the ultimate segments and the false indusia are longer, and the spores larger, in A. viridimontanum when compared to A. aleuticum.
Until 1991, the Green Mountain maidenhair fern was grouped with the western maidenhair fern, which grows both in western North America and as a disjunct
Disjunct distribution
In biology, a taxon with a disjunct distribution is one that has two or more groups that are related but widely separated from each other geographically...
on serpentine outcrops in eastern North America. At one time, western maidenhair fern was classified as a variety (A. pedatum var. aleuticum) of the northern maidenhair fern. However, after several years of study, the botanist Cathy Paris recognized that the western maidenhair constituted a separate species, and that some of the specimens that had been attributed to that taxon were a third, hybrid species. She named the new species A. viridimontanum for the site of its discovery in the Green Mountains
Green Mountains
The Green Mountains are a mountain range in the U.S. state of Vermont. The range extends approximately .-Peaks:The most notable mountains in the range include:*Mount Mansfield, , the highest point in Vermont*Killington Peak, *Mount Ellen,...
in Vermont
Vermont
Vermont is a state in the New England region of the northeastern United States of America. The state ranks 43rd in land area, , and 45th in total area. Its population according to the 2010 census, 630,337, is the second smallest in the country, larger only than Wyoming. It is the only New England...
. It has since been located in Quebec
Quebec
Quebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....
and in one site on serpentine in coastal Maine
Maine
Maine is a state in the New England region of the northeastern United States, bordered by the Atlantic Ocean to the east and south, New Hampshire to the west, and the Canadian provinces of Quebec to the northwest and New Brunswick to the northeast. Maine is both the northernmost and easternmost...
.
Due to its limited distribution and similarity to other Adiantum species within its range, little is known of its ecology. It thrives on sunny, disturbed areas where ultramafic rock is covered with thin soil, such as road cuts, talus
Scree
Scree, also called talus, is a term given to an accumulation of broken rock fragments at the base of crags, mountain cliffs, or valley shoulders. Landforms associated with these materials are sometimes called scree slopes or talus piles...
slopes, and asbestos
Asbestos
Asbestos is a set of six naturally occurring silicate minerals used commercially for their desirable physical properties. They all have in common their eponymous, asbestiform habit: long, thin fibrous crystals...
mines. Individual plants seem long-lived, and new individuals only infrequently reach maturity. It is one of four species endemic to serpentine in eastern North America and is considered globally threatened due to its habitat restrictions.
Description
The Green Mountain maidenhair is a medium-sized, deciduousDeciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
fern. Its fronds range from 30 to 75 cm (11.8 to 29.5 in) in size. The rachis appears to fork into two outward- and backward-curving branches, which bear the penultimate segments of the leaf along the outer side of the curve. These are pinnately divided into the ultimate segments. While this structure is sometimes called pedate
Pedate
Pedate is a term used in biology to describe certain structures resembling feet, or the quality of having feet. It derives from the Latin verb "pedo", meaning "to furnish with feet".-Plants:...
, it is more accurately described as pseudopedate
Pseudopedate
Pseudopedate is a term used in botany to describe the leaf architecture of certain ferns in the genus Adiantum .-Plants:...
; the basal pinnae of the central penultimate segment are greatly enlarged and are further divided and subdivided to form the penultimate segments on either side.
The rhizome
Rhizome
In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...
shows little branching, with intervals of 4.0 to 7.5 mm between nodes. It measures 2.0 to 3.5 mm in diameter. The rhizome and the base of the stipe
Stipe (botany)
In botany, a stipe is a stalk that supports some other structure. The precise meaning is different depending on which taxonomic group is being described....
have bronze
Bronze
Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive. It is hard and brittle, and it was particularly significant in antiquity, so much so that the Bronze Age was named after the metal...
-colored scales. The stipe and rachis range from chestnut brown (castaneous) to dark purple (atropurpureous) in color and are glabrous; the stipe is about 2 to 3 mm in diameter while the rachis is smaller, 1 to 2 mm. The basal pinnae are from three to seven times pinnate (due to the pseudopedate structure of the blade), while the apical part of the blade (and the corresponding segments of the basal pinnae) are once-pinnate. This part of the blade (the apparent "pinna", or penultimate segment) is typically lanceolate in shape. The overall arrangement of the penultimate segments ranges from drooping and fan-shaped (flabellate) on plants growing in the shade to funnel-shaped on plants growing in full sun, in which case they stand stiffly erect.
The ultimate segments of the divided blade are borne on short, dark stalks of 0.6 to 1.5 mm, with the dark color often spreading into the base of each segment. They are long and obliquely triangular, the basiscopic margin forming the hypotenuse
Hypotenuse
In geometry, a hypotenuse is the longest side of a right-angled triangle, the side opposite the right angle. The length of the hypotenuse of a right triangle can be found using the Pythagorean theorem, which states that the square of the length of the hypotenuse equals the sum of the squares of the...
. The tip of the segments is typically acute, but entire (not pointed). They measure from 9.5 to 22.5 mm in length and 4.2 to 7.5 mm in breadth, the average length being about 2.5 times the breadth. Their tissue is firmly leafy (herbaceous) to papery (chartaceous) in texture, and bright green to bluish-green in color. As in other members of Adiantum, the glabrous leaves shed water when young. In shady conditions, the ultimate segments lie within the plane of the blade, but tend to twist out of the plane when grown in the sun. The acroscopic margins of these segments are lobed, with narrow (less than 1.0 mm) incisions lying between lobes. In fertile segments, these lobes are recurved to form false indusia beneath the leaf. These are transversely oblong, from 2 to 5 mm in length and from 0.6 to 1.4 mm in width.
The sori (clusters of spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
-bearing structures) are borne on the underside of the leaf beneath the false indusium. This characteristic is a synapomorphy
Synapomorphy
In cladistics, a synapomorphy or synapomorphic character is a trait that is shared by two or more taxa and their most recent common ancestor, whose ancestor in turn does not possess the trait. A synapomorphy is thus an apomorphy visible in multiple taxa, where the trait in question originates in...
for Adiantum: a trait found only in Adiantum and not in its closest relatives. (In fact, the sori under false indusia are not only unique to Adiantum but present in all its members.) The sori are round, and are found on veins ending in the false indusium, below the veins' ends. The spores are tetrahedral to globose, yellow in color, and measure 41 to 58 micrometers (μm) in diameter (averaging 51.4 μm), on average larger than other species in the A. pedatum complex. Spores appear in the summer and fall. The species has a chromosome number of n = 58.
Identification
Adiantum viridimontanum closely resembles the other species in the A. pedatum complex (A. pedatum and A. aleuticum), and distinguishing the three in the field is difficult. Paris and Windham, in their study of the complex, noted that while each species, collectively, can be distinguished from the others, no single morphological character was absolutely distinctive among species. "Successful identification of individual specimens, therefore, must depend upon simultaneous consideration of a number of qualitative and quantitative characters." Sterile triploid hybrids between A. viridimontanum and the other two species may occur, further complicating field identification.Another distinguishing character is the shape of the medial ultimate segments, which are oblong in A. pedatum and long-triangular or kidney-shaped (reniform) in A. viridimontanum some specimens of A. aleuticum. Furthermore, A. viridimontanum can grow in both shade and sun, while A. pedatum grows in shade only.
Adiantum viridimontanum can be separated from the morphologically similar individuals of A. aleuticum by the greater length of the stalks on the medial ultimate segments and of the false indusia, measuring greater than 0.9 mm and greater than 3.5 mm, respectively, in A. viridimontanum. Spore size is also a useful character ex situ; the average A. viridimontanum spore measures 51.4 μm in diameter. While A. aleuticum spores can reach up to 53 μm, they average about 43 μm. In A. aleuticum growing as a disjunct on eastern serpentine (the most likely specimens to be confused with A. viridimontanum), the rhizome is much more frequently branched, with intervals of 1.0 to 2.0 mm between nodes.
Taxonomy
Following the discovery of western maidenhair fernAdiantum aleuticum
Adiantum aleuticum is a species of fern in the genus Adiantum, native mainly to western North America from the Aleutian Islands of Alaska, south to Chihuahua, and also locally in northeastern North America from Newfoundland south to Maryland.The fronds grow to 15-110 cm high, and are...
(then classified as Adiantum pedatum var. aleuticum) on the serpentine tableland of Mount Albert
Mount Albert (Quebec)
Mont Albert is a mountain in the Chic-Choc range in the Parc national de la Gaspésie in the Gaspé Peninsula of eastern Quebec, Canada. At , it is one of the tallest mountains in southern Quebec, and is popular for hiking....
by Merritt Lyndon Fernald
Merritt Lyndon Fernald
Merritt Lyndon Fernald was an American botanist. In his time he was regarded as the most respected scholar of the taxonomy and phytogeography of the vascular plant flora of temperate eastern North America. He published more than 850 scientific papers and wrote and edited the seventh and eighth...
in 1905, botanists began to search for the fern on ultramafic outcrops elsewhere in Quebec
Quebec
Quebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....
and Vermont
Vermont
Vermont is a state in the New England region of the northeastern United States of America. The state ranks 43rd in land area, , and 45th in total area. Its population according to the 2010 census, 630,337, is the second smallest in the country, larger only than Wyoming. It is the only New England...
. It was first identified in Vermont by L. Frances Jolley in 1922 at Belvidere Mountain in Eden
Eden, Vermont
Eden is a town in Lamoille County, Vermont, United States. The population was 1,152 at the 2000 census.-Geography:According to the United States Census Bureau, the town has a total area of 64.3 square miles , of which 63.6 square miles is land and 0.7 square mile is water...
. In 1983, William J. Cody referred A. pedatum growing on serpentine, both in eastern and western North America, to A. pedatum ssp. calderi instead. Many of the stations for the fern in Vermont were described in 1985, in a survey of ultramafic outcrops in that state.
From 1983 to 1985, Cathy A. Paris, then a graduate student, gathered specimens of A. pedatum from non-serpentine soils in the Midwest and Vermont, and from serpentine soils in New England and Canada, for biosystematic analysis. In 1988, Paris and Michael D. Windham published a the results of this analysis, revealing A. pedatum in North America to be a cryptic species complex
Cryptic species complex
In biology, a cryptic species complex is a group of species which satisfy the biological definition of species—that is, they are reproductively isolated from each other—but whose morphology is very similar ....
. They showed that A. pedatum sensu lato included two well-distinguished diploid taxa, one found in the Eastern woodlands, and the other found both in the Western mountains and as a disjunct on serpentine in the East. However, not all of the serpentine disjuncts proved to belong to the Western taxon. Several of them, including most of the specimens in Vermont, were found to be tetraploid, forming a taxon distinguishable from the two diploids. Isozyme
Isozyme
Isozymes are enzymes that differ in amino acid sequence but catalyze the same chemical reaction. These enzymes usually display different kinetic parameters Isozymes (also known as isoenzymes) are enzymes that differ in amino acid sequence but catalyze the same chemical reaction. These enzymes...
banding patterns suggested that the tetraploid had arisen by hybridization between the eastern subspecies of non-serpentine woodlands and the western and serpentine taxon, followed by a duplication of the hybrid genome. This allotetraploid was also morphologically intermediate between the two taxa, although it more closely resembled the serpentine taxon (hence its earlier referral to var. aleuticum). Paris formally described the tetraploid as a new species, A. viridimontanum, in 1991, and also separated the western and serpentine taxon from A. pedatum as A. aleuticum. The type specimen of A. viridimontanum was collected from a talus slope at the old asbestos
Asbestos
Asbestos is a set of six naturally occurring silicate minerals used commercially for their desirable physical properties. They all have in common their eponymous, asbestiform habit: long, thin fibrous crystals...
mine on Belvidere Mountain on August 28, 1985. The sequencing of several chloroplast
Chloroplast
Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.Chloroplasts are green...
DNA loci has revealed that the A. viridimontanum chloroplast genome most closely resembles that of A. aleuticum, suggesting that A. aleuticum was the maternal parent of A. viridimontanum.
Distribution and habitat
Green Mountain maidenhair is narrowly distributed in New EnglandNew England
New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...
and Quebec
Quebec
Quebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....
. Seven stations in Vermont
Vermont
Vermont is a state in the New England region of the northeastern United States of America. The state ranks 43rd in land area, , and 45th in total area. Its population according to the 2010 census, 630,337, is the second smallest in the country, larger only than Wyoming. It is the only New England...
lie in the Missisquoi Valley
Missisquoi River
The Missisquoi River is a tributary of Lake Champlain, approximately 80 mi long, in northern Vermont in the United States and southern Quebec in Canada. It drains a rural area of the northern Green Mountains along the US-Canada border northeast of Lake Champlain, and an area of Quebec's Eastern...
, in the northern Green Mountain
Green Mountain
Green Mountain is a common name for "The Peak", the highest point, on Ascension Island which has gained some fame for claims that it is one of very few large-scale artificial forests.-History and Vegetation:...
s, giving the fern its name. The ultramafic rocks of this area extend northwards into Quebec, where eight stations are known in southern Quebec and six in the Thetford Mines area. It is also known from one station on serpentine on Deer Isle, Maine
Deer Isle, Maine
Deer Isle is a town in Hancock County, Maine, United States. The population was 1,876 at the 2000 census. Notable landmarks in Deer Isle are the Haystack Mountain School of Crafts and the town's many art galleries.-History:...
.
The fern thrives in thin serpentine soil
Serpentine soil
A serpentine soil is derived from ultramafic rocks, in particular serpentinite, a rock formed by the hydration and metamorphic transformation of ultramafic rock from the Earth's mantle....
s on sunny, disturbed habitats such as roadcuts and talus
Scree
Scree, also called talus, is a term given to an accumulation of broken rock fragments at the base of crags, mountain cliffs, or valley shoulders. Landforms associated with these materials are sometimes called scree slopes or talus piles...
slopes, in dunite
Dunite
Dunite is an igneous, plutonic rock, of ultramafic composition, with coarse-grained or phaneritic texture. The mineral assemblage is greater than 90% olivine, with minor amounts of other minerals such as pyroxene, chromite and pyrope. Dunite is the olivine-rich end-member of the peridotite group...
and other ultramafic rocks. Anthropogenic disturbance has removed thicker soils and increased sun exposure in many of these sites; for instance, many of the Quebec stations are in asbestos mines, both abandoned and active. In more natural habitats, frost weathering
Frost weathering
Frost weathering is a collective name for several mechanical weathering processes induced by stresses created by the freezing of water into ice. The term serves as an umbrella term for a variety of processes such as frost shattering, frost wedging and cryofracturing...
and erosion may promote rock fall and maintain suitable habitat.
The eastern serpentine outcrops where Green Mountain maidenhair thrives are largely depauperate of endemics compared to serpentine exposures globally. Green Mountain maidenhair is one of only five taxa (four species and a variety) recognized as strictly endemic to serpentine when they occur in eastern North America.
Ecology
Green Mountain maidenhair largely reproduces asexually by branching rather than sexually through spores. While wind-blown spores can result in sexual reproduction for the species, most spores probably fall within a relatively short radius of the plant. In addition, reproduction through spore dispersal requires the spore to land in suitable conditions for generating a gametophyteGametophyte
A gametophyte is the haploid, multicellular phase of plants and algae that undergo alternation of generations, with each of its cells containing only a single set of chromosomes....
, typically in bright sunlight on thin serpentine soils. These requirements allow Green Mountain maidenhair to colonize recently disturbed sites on ultramafic outcrops, where bedrock has been exposed and competing plants have been removed. The populations appear stable, with the long life of individuals compensating for low recruitment
Recruitment (biology)
In biology, recruitment occurs when juvenile organisms survive to be added to a population. The term is generally used to refer to a stage whereby the organisms are settled and able to be detected by an observer....
rates.
Little is known about the role of Green Mountain maidenhair in the ecosystem. In general, ferns are less susceptible to herbivory than angiosperms due to higher levels of toxic and distasteful compounds in their foliage. The Green Mountain maidenhair is not known to be threatened by a particular predator or disease.
Conservation
Under the NatureServe conservation status system, Green Mountain maidenhair is considered globally vulnerable (G3). In Vermont and Quebec it is considered imperiled (S2); it has not yet been classified in Maine.Conservation of Green Mountain maidenhair is primarily limited by its restricted habitat on serpentine cliffs and talus slopes. However, these sites are also of little value to humans. The most likely threat to the species is expansion of asbestos mining, which often occurs near populations of the fern, or other reuse of abandoned asbestos mines. Road construction might also threaten some sites, although this is mitigated by the fern's avidity for disturbed serpentine. None of the sites are as yet known to be invaded by non-native plants.