ESR 3:61-68 (2007)  -  doi:10.3354/esr003061

ABSTRACT: Occupancy and persistence in naturally isolated habitat patches were analyzed to evaluate patterns of local extinction of an endangered species, the Coachella Valley fringe-toed lizard Uma inornata. We examined 4 parameters: (1) habitat quality, (2) patch size, (3) patch connectivity, and (4) drought. The Coachella Valley in southern California’s Colorado Desert has a strong west–east gradient, with drier and more persistent drought conditions in the east. The distribution of habitats along this gradient was the best single factor explaining patch occupancy over 14 yr. Drought and patch size provided the best multivariate model. When the westernmost habitat patches were analyzed alone, patch size was the only statistically significant variable. Our results show how conservation planning criteria for species of concern can differ within a species’ range. In this instance, patches located in the eastern part of the valley may need to be much larger than those in the more mesic west. Applying one minimum habitat size criteria for conservation efforts throughout the lizards’ range could result in either not protecting viable populations (e.g. in the west) or spending limited conservation funds on protecting non-sustainable populations in the east (if the minimum size was too small). Identifying gradients that may impact population persistence and extinction across landscapes is an important step in effective conservation planning.

KEY WORDS: Patch size · Persistence · Extinction · Drought · Uma inornata · Conservation