Restoring arthropod communities in coastal sage scrub

Coastal sage scrub in California and northern Baja California has been severely affected by urban expansion and is, in places, badly in need of restoration. We measured arthropod abundance and diversity on one of its primary components, the native shrub Artemisia californica (Asteraceae; California sage), to evaluate whether arthropod communities had become reestablished after a restoration attempt. Arthropods were collected from shrubs on planted and undisturbed sites 6 years after a restoration attempt. Fifty-seven families and 146 adult morphospecies were found. Family and species richness were greater on planted shrubs, but arthropod diversity, once differences in species' abundances were corrected for, was greater on naturally established plants. Common arthropods occurred at similar densities regardless of planting history. The proportion of single occurrences of a species, in contrast, was significantly greater on naturally established shrubs. Planted shrubs supported more predators relative to herbivores than did naturally established shrubs. Planted shrubs were still distinguishable from naturally established ones in that they were both more isolated from neighboring shrubs and surrounded by more invasive weeds. We suggest that small-scale restoration attempts can be successful at restoring basic elements of surrounding biodiversity. They do create a different community, however, both taxonomically and functionally, and are at least initially less able to support rare species.