| Popis: |
The Gran Desierto of northwestern Sonora is one of the most arid regions of North America. The flora and vegetation of the Sierra del Rosario and the surrounding extensive dune system are analyzed and compared with each other. The dunes, covering on the order of 4,500 sq. km., support a flora of 75 species, while the Sierra, comprising approximately 78 sq. km., supports 105 species. The total flora consists of 145 species, with 36 species common to both the dunes and Sierra. The life -form spectra are indicative of extremely arid conditions: ephemeral species make up 55% of the total flora. A number of range extensions are reported. Mentzelia longiloba is reduced to a subspecies of M. multiflora. There are only three non-native, naturalized species among the dune flora, and none in the Sierra flora. There is no indication of endemism among the Sierra flora. In contrast, the dunes, when considered together with similar habitat in adjacent southeastern California and southwestern Arizona, show some level of evolutionary differentiation for approximately 15% of the flora. |
