Gulf of California Xeric Scrub
This taxon occurs in the Gulf of California xeric scrub ecoregion, situated along the eastern coastal zone and Gulf of California versant of the Baja Peninsula in Mexico, and is delineated by the spine of the La Giganta Sierra Mountains. This ecoregion, located entirely within the nation of Mexico, is classified within the Deserts and Xeric Scrublands biome. Species richness of plants is high in the ecoregion, but modest for fauna; however, endemism is high in this arid habitat, which receives some of the lowest precipitation in all of Mexico.
Dominant flora species are Creosote Bush (Larrea tridentata) and White Bursage (Ambrosia dumosa); moreover, other plant taxa occurring here include: Arizona Nettle-spurge (Jatropha cinerea), Desert Ironwood (Olneya tesota), Acacia brandegeana, Blue Palo Verde (Cercidium floridum), and Chloroleucon mangense var. leucospermum. Species of more mesic habitats occur on the many oases that are present on the Baja Peninsula: Mexican Fan Palm (Washingtonia robusta), Southern Cattail (Typha domingensis), Common Reed (Phragmites australis) and Date Palm (Phoenix dactylifera). The oases are remnants of more extensive mesic environments that existed in the peninsula in prehistoric times; these earlier habitats consisted of larger bodies of surface water distributed throughout the peninsula, surrounded by vegetation that belongs to wetlands interspersed with common elements of the xeric scrub.
The Isla Santa Catalina Leaf-toed Gecko (Phyllodactylus bugastrolepis) is an endemic reptile to the Gulf of California xeric scrub, occurring only on Isla Santa Catalina, and often found in dead cacti. Other reptile species found here include: the endemic Santa Catalina Island Whiptail (Cnemidophorus catalinensis), seen only on Santa Catalina Island in the Gulf of California; the endemic Santa Catalina Island Spiny Lizard (Sceloporus lineatulus); the endemic San Lorenzo Islands Lizard (Uta antiqua); the endemic Salsipuedes Island Whiptail (Cnemidophorus canus), restricted in occurrence to endemic to the islands of Salsipuedes, San Lorenzo Norte and San Lorenzo Sur ; the endemic Raza Island Leaf-toed Gecko (Phyllodactylus tinklei), found on Raza Island; the endemic Santa Cruz Leaf-toed Gecko (Phyllodactylus santacruzensis); the endemic Isla Partida Del Norte Leaf-toed Gecko (Phyllodactylus partidus), found solely on Isla Partida Norte and Cardonosa Este, in the Gulf of California; the endemic Angel Island Leaf-toed Gecko (Phyllodactylus angelensis), found only on several Gulf of California islands in the county of Islas Angel de la Guarda; the endemic Las Animas Island Gecko (Phyllodactylus apricus); and the near-endemic Marbled Whiptail (Cnemidophorus marmoratus), the latter of which occupies burrows in sandy soils.
There are a number of mammalian taxa present in the Gulf of California xeric scrub, including: Angel Island Mouse (Peromyscus guardia CR), an ecoregion endemic known only from Ángel de la Guarda Island in the northern Gulf of California, México; the ecoregion endemic Burt's Deermouse (Peromyscus caniceps CR), known only from Montserrat Island, Baja California Sur, Mexico; Baja California Rock Squirrel (Spermophilus atricapillus EN), a Baja California endemic; and the Fish-eating Bat (Myotis vivesi VU), which is found along in the coastal zone of Baja California and Sonora. Bunker's Woodrat (Neotoma bunkeri EX) was previously endemic to the ecoregion and is now extinct.
Baja California Desert Habitat
This taxon is found in the Baja California Desert ecoregion, located on most of the western side of the Baja Peninsula, containing varied habitats such as mountains, plains and coastal dunes. This desert is one of the largest and best preserved in Mexico, and due to its isolation, contains a high level of species richness and endemism. A series of ophiolytes (formations of gabrum, ultramafic rocks, and volcanic lava) surround the most prominent orographic feature: The San Andres mountain range. Overall, the climate is arid with variable temperature. The isolated nature of the peninsula, and its proximity to the sea, maintains a measure of humidity, and creates a stable diurnal temperature.
The predominant vegetation associations are composed of xeric scrub, which have been subdivided in diverse categories according to dominant species and the ecological conditions in which they occur. Thick-stemmed trees and shrubs, growing on rocky volcanic soils, cover the highest parts of the mountain ranges. Dominant plant species are Ambrosia camphorata, Common Stork's-bill (Erodium cicutarium), and Astragalus prorifer. The Boojumtree (Fouquieria columnaris) can be also found at elevations up to 1200m. Many species of cacti are present. Dominant species within the Baja California Desert vary with elevation. Epiphytes such as Small Ballmoss (Tillandsia recurvata) and Cudbear (Rocella tinctoria) grow in low elevation, humid areas, and account for a majority of the perennial vegetation. Areas previously submerged under the sea (in the Miocene era) are now covered by highly saline and alkaline-tolerant species, such as Ambrosia magdalenae, El Vizcaino Agave (Agave vizcainoensis), Datilillo (Yucca valida), Pitaya Agria (Stenocereus gummosus), and Porter's Muhly (Muhlenbergia porteri). Dune vegetation includes Creosote Bush (Larrea tridentata), Barclay's Saltbush (Atriplex barclayana), Rush Milkweed (Asclepias subulata) and Nicolletia trifida.
There are a number of reptilian taxa found in the Baja California Desert including the endemic Baja California Brush Lizard (Urosaurus lahtelai). The Baja California Legless Lizard (Anniella geronimensis EN) is also endemic to the ecoregion, and is restricted to a narrow strip around 87 kilometres (km) long, ranging from about six km north of Colonia Guerrero, southerly to a point south of Punta Baja at the northern edge of Bahia El Rosario. This legless lizard extends to at most four km inland in the Arroyo Socorro, but otherwise found only in the coastal zone; A. geronimensis also occurs on Isla San Gerónimo. Also found here is the San Lucan Leaf-toed Gecko (Phyllodactylus unctus NT), a species not endemic to the ecoregion, but restricted to the southern Baja Peninsula and the Gulf of California islands of Partida Sur, Gallo, Espiritu Santo, Ballena, Gallina and Cerralvo.
There are only a few amphibians found in the ecoregion. Anuran taxa occurring here include: California Chorus Frog (Pseudacris cadaverina); Pacific Chorus Frog (Pseudacris regilla); and Canyon Treefrog (Hyla arenicolor). Also found here is the Plateau Toad (Anaxyrus compactilis), an endemic to the lower central Mexican Plateau and Baja California Desert; another toad occurring in the ecoregion is the Western Toad (Anaxyrus boreas NT). The Channel Islands Slender Salamander (Batrachoseps pacificus) was earlier thought to occur in this ecoregion, but genetic data shows that this taxon is strictly endemic to the Channel Islands of California.
Endemic mammals include San Quintín Kangaroo Rat (Dipodomys gravipes CR), and Baja California Rock Squirrel (Spermophilus atricapillus EN). Other mammals that are classified as special status are the Lesser Long-nosed Bat (Leptonycteris yerbabuenae VU). Some shallow coastal saltwater lagoons protruding into the Baja California Desert along the Pacific Ocean provide key breeding habitat for the Grey Whale (Eschrichtius robustus CR). One of the largest such breeding waters is the remote San Ignacio Lagoon, extending many kilometres inland and rarely exceeding fifteen metres in depth.
Important sites for avian conservation include the Ojo de Liebre lagoon, along the Pacific coast, which is home to millions of overwintering ducks and geese. Bird species in the Baja California Desert include such notable raptor taxa as Golden Eagle (Aquila chrysaetos), Peregrine Falcon (Falco peregrinus), Southern Crested Caracara (Caracara plancus), Osprey (Pandion haliaeutus), and Burrowing Owl (Athene cunicularia).
Habitat and Ecology
This species is primarily found near water holes in the Gigantas Sierra and Sierra de San Francisco. It feeds on Datil plants. Because of this specific habitat preference, populations are very isolated and fragmented.
Molecular Biology and Genetics
Statistics of barcoding coverage: Spermophilus atricapillus
Public Records: 0
Specimens with Barcodes: 7
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
- 1996Lower Risk/least concern(Baillie and Groombridge 1996)
Baja California rock squirrel
- Álvarez-Castañeda, S. T., Castro-Arellano, I. & Lacher, T. (2008). Spermophilus atricapillus. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 8 January 2009.
- Helgen, Kristofer M.; Cole, F. Russel; Helgen, Lauren E.; and Wilson, Don E (2009). "Generic Revision in the Holarctic Ground Squirrel Genus Spermophilus". Journal of Mammalogy 90 (2): 270–305. doi:10.1644/07-MAMM-A-309.1. Archived from the original on 22 October 2011.
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