The past and present isolation of Sierra de la Laguna from the rest of the peninsula has played a major role in producing an extraordinary array of unique species. Isolation and their alleged history of contractions and expansion, has promoted high levels of speciation in dry forests of many tropical regions (Ceballos 1995). There are 224 species of vascular plants inhabiting Sierra de la Laguna dry forests. Of 138 species of spiders and collembola, 38 (27%) are found in the dry forest (Jiménez, 1988; Vázquez, 1988). Half the species the reptiles and amphibians of Sierra de la Laguna inhabit the dry forest habitat (Alvarez-Cárdenas et al. 1988), over 29 of 194 species of birds (Rodríguez-Estrella 1988), and 29 of 40 species of mammals (Gallina-Tessaro & Gonzalez 1988). The degree of endemism is high (Arriaga & Ortega 1988), and this is well demonstrated by the proportion of endemic species with respect to total recorded species: over ten percent of animal and plant species found at Sierra de la Laguna are endemic. This corresponds well with the fact that endemism in tropical dry forests is higher than in moist forests (Rzedowski 1993). The isolation of this region has contributed to a scarcity of predators, and to the poor competitive ability of some animals (Arriaga & Ortega 1988). Rodents and lagomorphs are virtually absent from the region, favoring the abundance of species that would otherwise be abated by direct competition with them (such is the case with the acorn woodpecker, Melanerpes formicivorus)( Rodríguez-Estrella 1988). Large areas of habitat still remain intact, as the topographical features make this ecoregion difficult to explore and exploit (Arriaga 1988).

Subtropical dry forests, with less than 500 millimeters  of precipitation per year, dominate lower portions of the mountains (300 to 800 meters in elevation). The trees in this region endure a long dry season during which, the majority of them lose leaves. The forest is transitional both with the pine oak forests at higher elevations, and with the xeric scrub at lower portions. The dry forest of Sierra de la Laguna is characterized by abundance of low trees and scrubs, and poor vertical stratification. The dominant tree species in the subtropical forest are Mauto (Lysiloma divaricatum), Palo Blanco (L. candida), Elephant Tree (Bursera microphylla) and Palo Zorrillo (Hesperalbizia occidentalis). Herbaceous elements are poorly developed, but their representatives are Caribe (Cnidoscolus angustidens), Spiny Aster (Chloracantha spinosa var. strictospinosa), Solanum spp., and cacti such as Biznaga (Ferocactus spp). Given its biological and climate, the Sierra de la Laguna dry forest is not analogous to the more continental dry forests located in Sonora and other parts of Mexico.