Patterns of occurrence of reptiles across a sand dune landscape

Abstract

Identifying variables that drive population dynamics is a critical component of conservation and guides decisions for maintaining sustainable populations. Our objective was to model spatial and temporal patterns of occurrence of reptiles across an aeolian sand landscape. We used a community framework based on dune geomorphology and wind-precipitation gradients to identify variables that explain patterns of reptile abundance. We found that although population dynamics in arid environments are typically correlated with precipitation, in some instances that pattern was weak or absent. Strong precipitation-related abundance patterns were found with Coachella Valley fringe-toed lizards ( Uma inornata), and zebra-tailed lizards ( Callisaurus draconoides). The strength of that relationship varied along a precipitation gradient. We found weak or no precipitation relationships with long-lived, territorial species such as desert iguanas ( Dipsosaurus dorsalis) and with species foraging on detritivore insects which appeared to not correlate with rainfall. In addition to precipitation our analyses allowed us to identify the influences of sand compaction, shrub density and exotic plant species, and how they varied between species and communities. Our approach broke down the inherent landscape complexity into tractable units that yielded information directly applicable to land managers and to the conservation of the species that comprise these communities.