No abstract

Globally, no species is exempt from the constraints associated with limited available habitat or resources, and endangered species in particular warrant critical examination. In most cases, these species are restricted to limited locations, and the relative likelihood of resource use within the space they can access is important. Using Gambelia sila, one of the first vertebrate species listed as endangered, we used resource selection function analysis of telemetry and remotely sensed data to identity key drivers of selected versus available locations for this species in Carrizo Plain National Monument, USA. We examined the probability of selection given different resource types. Increasing shrub cover, lower and relatively more flat sites, increasing normalized difference vegetation index, and solar radiation all significantly predicted likelihood of observed selection within the area sampled. Imagery data were also validated with fine-scale field data showing that large-scale contrasts of selection relative to available location patterns for animal species are a useful lens for potential habitat. Key environmental infrastructure such as foundation plant species including shrubs or local differences in the physical attributes were relevant to this endangered species.

The open source and free programming language R is a phenomenal mechanism to address a multiplicity of challenges in ecology and evolution. It is also a complex ecosystem because of the diversity of solutions available to the analyst. Packages for R enhance and specialize the capacity to explore both niche data/experiments and more common needs. However, the paradox of choice or how we select between many seemingly similar options can be overwhelming and lead to different potential outcomes. There is extensive choice in ecology and evolution between packages for both fundamental statistics and for more specialized domain‐level analyses. Here, we provide a checklist to inform these decisions based on the principles of resilience, need, and integration with scientific workflows for evidence. It is important to explore choices in any analytical coding environment—not just R—for solutions to challenges in ecology and evolution, and document this process because it advances reproducible science, promotes a deeper understand of the scientific evidence, and ensures that the outcomes are correct, representative, and robust.

Arthropods underpin arid community dynamics and provide many key ecosystem services. In arid ecosystems, the key habitat components that influence arthropod community structure are relatively understudied. Ephedra californica is a locally abundant shrub now restricted to highly fragmented populations with established positive effects on plant and vertebrate animal communities within the drylands of Southern California. The capacity for these positive effects to further support ground arthropod communities has not been examined. We tested the hypothesis that the physical structure and cover vegetation enhance key measures of arthropod community assembly at nine Californian desert sites that comprise an extensive regional aridity gradient. We contrasted the effects of shrub canopies with ground-covering vegetation on structuring ground-active arthropod communities by surveying ground-active arthropods with pitfall traps and collecting vegetation on the soil surface in the form of residual dry matter (RDM). We collected a total of 5820 individual arthropod specimens for a total of 159 morphospecies. Arthropod abundance and morphospecies richness and RDM biomass and cover were significantly greater beneath the canopy of E. californica throughout the region. Total biomass of RDM did not significantly influence arthropod communities, but cover of RDM on the soil surface negatively influenced arthropod abundance. Neither climatic aridity nor downscaled evaporative stress estimates were significant mediators of the arthropod-vegetation association patterns. Vegetation thus likely has direct and indirect physical effects on arthropod communities. These canopy vs. soil surface vegetation differences will refine sampling of finescale patterns of arthropod diversity in drylands. Regional land managers can support arthropod diversity by maintaining populations of foundation shrub species such as E. californica.

The biodiversity–ecosystem function literature provides a useful framework to examine many processes associated with species diversity in ecology. One such context is the maintenance of biodiversity by facilitation in arid ecosystems. Here, we examined the complex interactions between local plant species richness and the intensity of shrub facilitation for maintaining biodiversity in arid plant communities. A synthesis including a meta‐analysis was used to compile nearly 600 papers on positive interactions mediated by shrubs in dryland plant communities (search terms: shrub, positive, facilitat*) to examine whether interactions in these studies changed with reported local species richness. A total of 19 studies and 141 independent instances directly examined and reported facilitation of diversity measures in naturally assembled plant communities and provided estimates of local species richness. Synthesis. The net effect of increasing local plant species richness was negative and shifted the relative frequency of interactions with shrubs from positive to negative with increasing local species richness. This relationship suggests that increases in richness do not always enhance functions that maintain diversity in plants communities likely due to concurrent increases in the indirect negative interactions between species under shrubs or in changes in the local species pool.