The Hickory Nut Gorge green salamander (''Aneides caryaensis'') is a species of lungless

salamander Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All t ...

in the family

Plethodontidae Plethodontidae, or lungless salamanders, are a family of salamanders. Most species are native to the Western Hemisphere, from British Columbia to Brazil, although a few species are found in Sardinia, Europe south of the Alps, and South Korea. In ...

. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to the

Hickory Nut Gorge Hickory is a common name for trees composing the genus ''Carya'', which includes around 18 species. Five or six species are native to China, Indochina, and India (Assam), as many as twelve are native to the United States, four are found in Mexi ...

in the state of

North Carolina North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia and ...

in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

Taxonomy

It is a member of the subgenus '' Castaneides'', which contains the only members of the genus '' Aneides'' that inhabit the eastern half of North America, including the green salamander (''Aneides aeneus'') and two

undescribed taxa In taxonomy, an undescribed taxon is a taxon (for example, a species) that has been discovered, but not yet formally described and named. The various Nomenclature Codes specify the requirements for a new taxon to be validly described and named. U ...

. It was formerly considered a population of the green salamander until a study in 2019 found it to represent a distinct species and described it as such. Based on genetic evidence, it is the most basal member of the subgenus ''Castaneides'', and forms a clade entirely distinct from the other three likely species in the subgenus. A distinct population of ''A. aeneus'' of the Blue Ridge Escarpment (possibly another ''Castaneides''

cryptic species In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

) can be found just 25 km west of ''A. caryaensis'''s range in the Hickory Nut Gorge, but both taxa are genetically distinct, indicating a lack of gene flow between either species. Although no obvious surface barrier separates either species, three

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretace ...

-aged faults lie in the gap between the species distribution; activity in these fault regions during the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

likely altered the surrounding habitat into a more

grassland A grassland is an area where the vegetation is dominated by grasses ( Poaceae). However, sedge ( Cyperaceae) and rush ( Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur na ...

-dominated area unsuitable for ''Aneides'' species, isolating them in

relict A relict is a surviving remnant of a natural phenomenon. Biology A relict (or relic) is an organism that at an earlier time was abundant in a large area but now occurs at only one or a few small areas. Geology and geomorphology In geology, a r ...

forest habitats such as those that existed in the Hickory Nut Gorge. Around the same time, another relict forest may have existed in the Cumberland Plateau that also hosted an ''Aneides'' taxon; the descendants of this Cumberland taxon may have recolonized the

Appalachian Mountains The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They ...

(as opposed to the ancestor of ''A. caryaensis'', which stayed in its relict habitat in Hickory Nut Gorge) after the forest grew back, and may represent all the other species in the genus ''Castaneides''; this may be why ''A. caryaensis'' is so basal to all other species in the subgenus. Prior to the habitat changes in the Miocene, ''Castaneides'' species may have reached as far east as the

Piedmont it, Piemontese , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = , demographics1_footnotes = , demographics1_title1 = , demographics1_info1 = , demographics1_title2 ...

, inhabiting

lowland Upland and lowland are conditional descriptions of a plain based on elevation above sea level. In studies of the ecology of freshwater rivers, habitats are classified as upland or lowland. Definitions Upland and lowland are portions of p ...

habitats and having a more

arboreal Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. The habitats pose nu ...

lifestyle.

Distribution

This species is restricted to the Hickory Nut Gorge, a 20,000-acre, 14-mile long canyon in the

Blue Ridge Mountains The Blue Ridge Mountains are a Physiographic regions of the world, physiographic province of the larger Appalachian Mountains range. The mountain range is located in the Eastern United States, and extends 550 miles southwest from southern Pennsy ...

of North Carolina. Due to this comparatively very small distribution, it is considered a microendemic species. As with ''A. aeneus'', it inhabits crevices & hollows of rock outcrops and woody & arboreal habitats within cove forests, although it primarily depends on the former. Most nesting sites are on rock faces, likely leading to patchily distributed breeding populations.

Description

Aside from genetic differences, it can be physically distinguished from ''A. aeneus'' by a tail length (TL) that is longer than its snout to vent length (SVL), as well as its smaller and less-connected lichen-like patches of bright to yellowish-green pigment on a dark body, as opposed to the larger and more-connected patches of green on ''A. aeneus''.

Status

''A. caryaensis'' has an extremely narrow range and, despite intensive searches, is known from only 25 localities. Most of these populations have very low population densities with only a few individuals reported for each locality, and genetic analyses indicate low genetic diversity in these populations, indicating a high level of

inbreeding Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically. By analogy, the term is used in human reproduction, but more commonly refers to the genetic disorders and o ...

. The estimated population is only 250 individuals, although this may be an underestimate. The top threat to the species is

habitat loss Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

and fragmentation from

tourism Tourism is travel for pleasure or business; also the theory and practice of touring, the business of attracting, accommodating, and entertaining tourists, and the business of operating tours. The World Tourism Organization defines tourism mor ...

real estate development Real estate development, or property development, is a business process, encompassing activities that range from the renovation and re-lease of existing buildings to the purchase of raw land and the sale of developed land or parcels to other ...

, and the construction of

transportation Transport (in British English), or transportation (in American English), is the intentional movement of humans, animals, and goods from one location to another. Modes of transport include air, land (rail and road), water, cable, pipeline, ...

and

energy infrastructure Energy development is the field of activities focused on obtaining sources of energy from natural resources. These activities include production of renewable, nuclear, and fossil fuel derived sources of energy, and for the recovery and reuse ...

in the Hickory Nut Gorge. Due to the species being spread patchily across the landscape, habitat fragmentation and loss can easily occur. For these purposes, the species is considered

critically imperiled The NatureServe conservation status system, maintained and presented by NatureServe in cooperation with the Natural Heritage Network, was developed in the United States in the 1980s by The Nature Conservancy (TNC) as a means for ranking or categ ...

NatureServe NatureServe, Inc. is a non-profit organization based in Arlington County, Virginia, US, that provides proprietary wildlife conservation-related data, tools, and services to private and government clients, partner organizations, and the public. Nat ...

. Necessary protection actions include protecting areas of known and potential habitat from development and maintaining habitat connectivity to facilitate dispersal. The Center for Biological Diversity petitioned the U.S. Fish and Wildlife Service to protect the salamander under the Endangered Species Act in June 2022.

References

{{taxonbar, from = Q105806628 Aneides Amphibians of the United States Endemic fauna of North Carolina Amphibians described in 2019 Ecology of the Appalachian Mountains