Ensatina

The ensatina (Ensatina eschscholtzii) is a species complex of plethodontid (lungless) salamanders[2] found in coniferous forests, oak woodland and chaparral[3] from British Columbia, through Washington, Oregon, across California (where all seven subspecies variations are located), all the way down to Baja California in Mexico. The genus Ensatina originated approximately 21.5 million years ago.[4] It is usually considered as monospecific, being represented by a single species, Ensatina eschscholtzii, with several subspecies forming a ring species.

Ensatina
Yellow-eyed ensatina (Ensatina eschscholtzii xanthoptica)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Urodela
Family: Plethodontidae
Subfamily: Plethodontinae
Genus: Ensatina
Gray, 1850
Species:
E. eschscholtzii
Binomial name
Ensatina eschscholtzii
Gray, 1850
Synonyms
  • Ensatina klauberi
  • Heredia oregonensis
  • Plethodon croceater
  • Urotropis platensis

Habitat and description
Ensatina eschscholtzii klauberi, the large-blotched ensatina
E. eschscholtzii eschscholtzi, the Monterey ensatina

The ensatina subspecies E. e. eschscholtzii, or Monterey ensatina, can be found in Santa Cruz, Monterey, and the California coastal mountains. They reach a total length of three to five inches, and can be identified primarily by the structure of the tail, and how it is narrower at the base. This salamander is the only type that has this tail structure and five toes on the back feet.

Males often have longer tails than the females, and many of the salamanders have lighter colored limbs in comparison to the rest of the body. The salamanders lay their eggs underground, often in threes, which then hatch directly into salamanders, skipping the usual aquatic phase.

The ensatina subspecies Ensatina klauberi, or large blotched ensatina, can be found along the mountain ranges in Southern California, as well as a small region in Sierra Juarez, a mountain range located in northern Baja California.

Ensatina klauberi are similar in size to E. eschscholtzii; they are mid-sized with adults ranging from 3-6 inches in length. Females tend to have shorter and wider bodies compared to their male counterparts. This subspecies differs from E. eschscholtzii in their coloration. They are nearly black in color with blotches of orange that are present from their tail to their heads, and they have dark eyes. [5]

They are generally thought to be found in high elevations, from 520 to 2400m, in conifer forests and oak woodlands. However, populations were discovered along the coast in Volcán Riveroll, a volcanic area located in Baja California. It is thought that they are able to survive in this anomalous region due to the high moisture that comes in from the coast. It is unclear how these populations were able to end up in this coastal region, but it is hypothesized that “the subspecies was once more broadly distributed and became isolated as a result of climate change during the late Pleistocene and Holocene.” [6] If this is true, then it is estimated that Ensatina klauberi has been living in this region for thousands of years.

As a ring species

Ensatina eschscholtzii has been described as a ring species in the mountains surrounding the Californian Central Valley.[2] The complex forms a horseshoe shape around the mountains, and though interbreeding can happen between each of the 19 populations around the horseshoe, the Ensatina eschscholtzii subspecies on the western end of the horseshoe cannot interbreed with the Ensatina klauberi on the eastern end.[7] As such, it is thought to be an example of incipient speciation, and provides an illustration of "nearly all stages in a speciation process" (Dobzhansky, 1958).[2][8] Richard Highton argued that Ensatina is a case of multiple species and not a continuum of one species (meaning, by traditional definitions, it is not a ring species).[9]

Human contact

The ensatina can usually be found under logs or brush, by or in streams and lakes, and in other moist places. They are easily distressed by improper handling, because they rely on cutaneous respiration, their thin skin is very sensitive to heating, drying and exposure to chemicals from warm hands. They may exude a sticky milky secretion from the tail[10]

Subspecies
E. e. platensis from Fresno County, California
  • Yellow-blotched ensatina — E. e. croceater (Cope, 1868)
  • Monterey ensatina — E. e. eschscholtzii Gray, 1850
  • Large-blotched ensatina — E. e. klauberi Dunn, 1929
  • Oregon ensatina — E. e. oregonensis (Girard, 1856)
  • Painted ensatina — E. e. picta Wood, 1940
  • Sierra Nevada ensatina — E. e. platensis (Jiménez de la Espada, 1875)
  • Yellow-eyed ensatina — E. e. xanthoptica Stebbins, 1949

References
  1. IUCN SSC Amphibian Specialist Group (2015). "Ensatina eschscholtzii". IUCN Red List of Threatened Species. 2015: e.T59260A53979540. doi:10.2305/IUCN.UK.2015-4.RLTS.T59260A53979540.en. Retrieved 13 November 2021.
  2. Wake, D. (1997) Incipient species formation in salamanders of the Ensatina complex Proceedings of the National Academy of Sciences USA 94:7761-7767
  3. Monterey Ensatina San Diego Field Station, United States Geological Survey Viewed: April 24, 2005, Last updated: March 05, 2003
  4. Carl T. Bergstrom; Lee Alan Dugatkin (2012). Evolution. Norton. p. 468. ISBN 978-0-393-92592-0.
  5. Grismer, L. Lee (2019-12-31). Amphibians and Reptiles of Baja California, Including Its Pacific Islands and the Islands in the Sea of Cortés. University of California Press. doi:10.1525/9780520925205. ISBN 978-0-520-92520-5.
  6. Valdez-Villavicencio, Jorge Heriberto; Peralta-Garcia, Anny; Hollingsworth, Bradford Damion (2015-05-01). "A coastal population of Large-blotched Ensatina Ensatina klauberi (Caudata: Plethodontidae) in Baja California, México". Check List. 11 (3): 1649. doi:10.15560/11.3.1649. ISSN 1809-127X.
  7. Dawkins, R. (2004) The Ancestor's Tale: A Pilgrimage to the Dawn of Life ISBN 0-618-00583-8, Ring Species (The Salamander's Tale)
  8. Dobzhansky T. (1958) in A Century of Darwin, ed Barnett S A (Harvard Univ. Press, Cambridge, MA), pp 19–55.
  9. Highton, Richard (June 1998). "Is Ensatina eschscholtzii a Ring-Species?". Herpetologica. 54 (2): 254–278. JSTOR 3893431.
  10. Kupta, Shawn R (April 2008). "Why does the yellow-eyed Ensatina have yellow eyes? Batesian mimicry of Pacific newts (genus Taricha) by the salamander Ensatina eschscholtzii xanthoptica". Evolution. 62 (4): 984–990. doi:10.1111/j.1558-5646.2008.00338.x. PMID 18248632. S2CID 998486.
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