Espíritu Santo antelope squirrel

The Espíritu Santo antelope squirrel (Ammospermophilus insularis) is a species of antelope squirrel in the family Sciuridae.[2] It is endemic to Mexico, where it is known only from the island of Espíritu Santo in the Gulf of California. The species was originally described by Edward William Nelson and Edward Alphonso Goldman in 1909 as a subspecies of the white-tailed antelope squirrel (Ammospermophilus leucurus), a wide-ranging species in the southwestern U.S. and Mexico.[3] In 1938, Arthur H. Howell elevated the subspecies to full species status, on the basis of slightly larger skull proportions and the absence or reduction of the third upper premolar.[4] Studies of DNA and chromosomes have variously suggested close relationships with Harris's antelope squirrels (A. harrisii) or other subspecies of white-tailed antelope squirrel.[5] A 2007 comparison of DNA and morphological traits suggested the differences between Espíritu Santo squirrels and those on the Baja California peninsula and other islands were not enough to warrant distinct species but rather a subspecies of white-tailed antelope squirrels.[6] Since 2008 the IUCN has similarly recognized the Espíritu Santo antelope squirrel as a subspecies of white-tailed antelope squirrel.[7]

Espíritu Santo antelope squirrel
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Sciuridae
Genus: Ammospermophilus
Species:
A. insularis
Binomial name
Ammospermophilus insularis
(Nelson & Goldman, 1909)
Synonyms
  • Ammospermophilus leucurus insularis
  • Citellus insularis

[1]

Description

Ammospermophilus insularis diverged from Ammospermophilus leucurus species (specific to southern Baja California peninsula) and display similar characteristics. Both species contain two defined black bands alternating with three white bands on the underside of the tail.[8] There are, however, several unique traits that distinguish A. insularis from A. leucurus. A. insularis males and females are slightly larger and darker compared to A. leucurus and display missing or vestigial upper premolar.[9][10][11] An upper premolar is generally variable among the family Sciuridae but is significantly different as seen in A. insularis compared to other Ammospermophilus species. A larger skull is also observed in A. insularis, specifically the zygomatic arches, nasals, and auditory bullae.

Biogeography

A. insularis is distributed in specific location of Mexican state regions. It is found in the Nearctic sub region, Californian Dominion, Baja California Province, and Baja California Sur Mexican state.[12] There are three major lineages of the Ammospermophilus including, A. nelsoni, A. leucurus, and A. harrisii. Geographic isolation of A. leucurus gave rise to the sub species A. insularis.[13] A. insularis inhabits rocky desert environments in Baja California Sur, Mexico including Isla Espiritu Santo and Isla San Marcos. The elevation range is from sea level to about 600 meters above sea level and generally not seen in higher elevation coniferous forests.

Phylogenetic History

A. insularis diverged from the southern Baja California lineage A. leucurus. Cytochrome B data analysis displays a divergence value of 2% indicating intraspecific variation.[14] Haplotypes have also displayed an overlap and close resemblance between A. insularis and A. leucurus. Even though the A. insularis haplotypes are monophyletic, they are nested within the A. leucurus lineage.[15] Glacial expansion and retreat during the Pleistocene resulted in isolation of the genus Ammospermophilus leading to divergence into its three general groups. Southern Baja California A. leucurus species diverged approximately 2.5 million years ago somewhere between the end of the Pliocene and beginning of Pleistocene era. A. insularis diverged from A. leucurus about 640,00 years ago during Pleistocene era.[16]

References
  1. Goodwin, Thomas (14 August 2009). "Odontometric Patterns in the Radiation of Extant Ground-Dwelling Squirrels Within Marmotini (Sciuridae: Xerini)". Journal of Mammalogy. 90 (4): 1009–1019. doi:10.1644/08-MAMM-A-229.1. ISSN 0022-2372.
  2. Thorington, R.W., Jr.; Hoffman, R.S. (2005). "Family Sciuridae". In Wilson, D.E.; Reeder, D.M (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 797. ISBN 978-0-8018-8221-0. OCLC 62265494.
  3. Nelson & Goldman (1909). "Eleven new mammals from Lower California". Proceedings of the Biological Society of Washington. 22: 23–28.CS1 maint: uses authors parameter (link)
  4. Howell, Arthur H. (1938). "Revision of the North American Ground Squirrels, with a Classification of the North American Sciuridae". North American Fauna. 56: 1–256. doi:10.3996/nafa.56.0001. hdl:2027/msu.31293201256918.
  5. Best T. L., Caesar K., Trrus A. S., Lewis C. L. (1990). "Ammospermophilus insularis" (PDF). Mammalian Species (364): 1–4. doi:10.1093/mspecies/364.1. Archived from the original (PDF) on 2016-03-04. Retrieved 2015-06-24.CS1 maint: uses authors parameter (link)
  6. Álvarez-Castañeda, Sergio T. (2007). "Systematics of the Antelope Ground Squirrel (Ammospermophilus) from Islands Adjacent to the Baja California Peninsula". Journal of Mammalogy. 88 (5): 1160–1169. doi:10.1644/06-MAMM-A-065R3.1.
  7. Linzey, A.V.; Timm, R.; Álvarez-Castañeda, S.T.; Castro-Arellano, I.; Lacher, T. (2008). "Ammospermophilus leucurus". IUCN Red List of Threatened Species. 2008. Retrieved 23 June 2015.CS1 maint: ref=harv (link)
  8. Mantooth, Stacy J.; Hafner, David J.; Bryson, Jr, Robert W.; Riddle, Brett R. (February 14, 2013). "Phylogeographic diversification of antelope squirrels (Ammospermophilus) across North American deserts". Biological Journal of the Linnean Society. 109 (4): 949–967. doi:10.1111/bij.12084.
  9. Mantooth, Stacy J.; Hafner, David J.; Bryson, Jr, Robert W.; Riddle, Brett R. (February 14, 2013). "Phylogeographic diversification of antelope squirrels (Ammospermophilus) across North American deserts". Biological Journal of the Linnean Society. 109 (4): 949–967. doi:10.1111/bij.12084.
  10. Matějů, Jan; Kratochvíl, Lukáš (2013). "Sexual size dimorphism in ground squirrels (Rodentia: Sciuridae: Marmotini) does not correlate with body size and sociality". Frontiers in Zoology. 10 (1): 27. doi:10.1186/1742-9994-10-27. PMC 3663772. PMID 23672689.
  11. Goodwin, Thomas H. (2009). "Odontometric Patterns in the Radiation of Extant Ground-dwelling Squirrels within Marmotini (Sciuridae: Xerini)". Journal of Mammalogy. 90 (4): 1009–1019. doi:10.1644/08-MAMM-A-229.1.
  12. Escalante, Tania; Sánchez‐Cordero, Víctor; Morrone, Juan J.; Linaje, Miguel (4 June 2007). "Deforestation affects biogeographical regionalization: a case study contrasting potential and extant distributions of Mexican terrestrial mammals". Journal of Natural History. 41 (13–16): 965–984. doi:10.1080/00222930701292062.
  13. Mantooth, Stacy J. "From the valleys to the mountains: e biographic history of antelope squirrels, bats, and chipmunks in Western North America". http://digitalscholarship.unlv.edu/cgi/viewcontent.cgi?article=1022. UNLV. Retrieved 18 November 2016. External link in |website= (help)
  14. Mantooth, Stacy J.; Hafner, David J.; Bryson, Jr, Robert W.; Riddle, Brett R. (February 14, 2013). "Phylogeographic diversification of antelope squirrels (Ammospermophilus) across North American deserts". Biological Journal of the Linnean Society. 109 (4): 949–967. doi:10.1111/bij.12084.
  15. Mantooth, Stacy J. "From the valleys to the mountains: e biographic history of antelope squirrels, bats, and chipmunks in Western North America". http://digitalscholarship.unlv.edu/cgi/viewcontent.cgi?article=1022. UNLV. Retrieved 18 November 2016. External link in |website= (help)
  16. Mantooth, Stacy J. "From the valleys to the mountains: e biographic history of antelope squirrels, bats, and chipmunks in Western North America". http://digitalscholarship.unlv.edu/cgi/viewcontent.cgi?article=1022. UNLV. Retrieved 18 November 2016. External link in |website= (help)
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