Ecology

Habitat

San Lucan Xeric Scrub Habitat

This taxon is found in the San Lucan xeric scrub, an ecoregion situated at the southern-most part of the Baja Peninsula of Mexico; this diverse landscape of mountains, valleys, and plateaus is covered with a variety of species of xeric vegetation. This neotropical ecoregion is classifed within the Deserts and Xeric Scrublands biome. Plants and animals of this region evolved independently before the Baja Peninsula, a previous island during the Miocene, joined the mainland. An arid climate supports a number fauna and species, about ten percent which of which are endemic.

The ecoregion took shape in the Miocene as an isolated landform prior to joining the peninsula, and thus can be considered an biogeographical island of vegetation. This arid landscape is composed of a vast, rugged complex of granitic mountains, valleys, canyons, and plateaus. The ecoregion occupies the plateaus between the coast and the lower limits of the dry forests, which begin around 250 meters. Precipitation is about 400 millimetres annually.

Some elements of dry forest habitat are present in this ecoregion, but xeric elements are dominant and include Chain-link Cholla (Opuntia cholla); Elephant Tree (Bursera microphylla), at the southern limit of its range here and extending north to the Waterman Mountains in the USA; Mauto (Lysiloma divaricata); Organ Pipe Cactus (Stenocereus thuberi), Mala Mujer (Cnidoscolus angustidens), Yucca spp., and Barrel Cacti (Ferocactus spp). Herbaceous elements in the ecoregion include Plantago linearis, Bouteloua hirsuta, and Commelina coelestis.

The San Lucan xeric scrub harbours 31 of 48 of the reptile species for the Cape Region. Almost a third of the wider regional recorded species of collembola arthropods and spiders (30 of 138 species, respectively) occur in this ecoregion. In general, over ten percent of animal and plant species found here are endemic.

Within the San Lucan xeric scrub ecoregion, reptilian taxa include: the endemic Island Burrowing Sand Snake (Chilomeniscus punctatissimus); the endemic Isla Cerralvo Snake (Chilomeniscus savagei), restricted solely to Cerralvo Island; the Cape Arboreal Spiny Lizard (Sceloporus licki), a near-endemic restricted to the southern portion of the Baja Peninsula; the near-endemic Spiny Chuckwalla (Sauromalus hispidus NT), found only on Angel de la Guarda Island, Granito, Mejía, Pond, San Lorenzo Norte, San Lorenzo Sur, and other islands in Bahía de los Ángeles, including Cabeza de Caballo, La Ventana, Piojo, Flecha, Mitlàn, and Smith, Gulf of California; the near-endemic San Lucan Leaf-toed Gecko (Phyllodactylus unctus NT), found only on southern Baja Peninsula and some islands within the Gulf of California: Gallo, Partida Sur, Espiritu Santo, Ballena, Gallina and Cerralvo. There are only a small number of anuran species present in the ecoregion: Red-spotted Toad (Anaxyrus punctatus); and Pacific Chorus Frog (Pseudacris regilla).

The Espiritu Santo Island Antelope Squirrel (Ammospermophilus insularis) is endemic to the San Lucan xeric scrub ecoregion and is found only on the island of Espiritu Santo in the Gulf of California. Among threatened mammals occurring in the ecoregion are: the near-endemic Dalquest's Pocket Mouse (Chaetodipus dalquesti VU), known from the Cape Region of the Baja California Peninsula.

Threatened mammals in the ecoregion include: the near-endemic Peninsular Myotis (Peninsular Myotis EN), found only on southern Baja Peninsula; Fish-eating Bat (Myotis vivesi VU), a near-endemic occurring chiefly on the near-shore islands off of the southern Baja Peninsula and mainland Sonora; Mexican Long-tongued Bat (Choeronycteris mexicana NT); and the Lesser Long-nosed Bat (Leptonycteris yerbabuenae VU).

Creative Commons Attribution 3.0 (CC BY 3.0)

© C. Michael Hogan & World Wildlife Fund

Supplier: C. Michael Hogan

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