DOI: 10.6075/j069724p
title: Native bees in San Diego's coastal sage scrub reserves and fragments, surveyed in 2015 and 2016

description: Data collection occurred in 1-ha study plots embedded in large natural reserves and habitat fragments that span a gradient with respect to their internal area of contiguous scrub habitat. Both reserve plots and fragment plots were chosen from areas that contained a diversity of native perennial shrubs, dominated by combinations of Acmispon glaber (Vogel) Brouillet, Artemisia californica Less., Bahiopsis laciniata (A. Gray) E. E. Schilling & Panero, Eriogonum fasciculatum Bentham, Malosma laurina (Nutt.) Abrams, Rhus integrifolia (Nutt.) Brewer & S. Watson, and Salvia mellifera E. Greene. To the extent possible, study plots were chosen at sites with minimal invasion by exotic forbs such as Brassica nigra (L.) Koch, and Erodium spp., and exotic grasses such as Avena spp. and Bromus spp. Reserve plots were chosen within three distinct reserves: Elliott Chaparral Reserve of the University of California Reserves System (plots ECR4 and ECR5), Mission Trails Regional Park (plots MTE3 and MTE4), and the Otay-Sweetwater unit of the San Diego National Wildlife Refuge (plots SWEA and SWI4). Fragment plots were chosen in the vicinity of reserve plots (maximum distance between fragment and reserve plots &lt; 15 km) and consisted of well-preserved scrub habitat surrounded by urban, residential infrastructure such as roads (two lanes minimum), buildings, and paved lots. One researcher, KLJH, sampled bees at all study plots via bowl-trapping, on sunny days with light wind. Bowl traps consisted of plastic bowls 7 cm in diameter that were white (left unpainted) or painted fluorescent blue or fluorescent yellow and filled with roughly 60 ml of unscented detergent solution. During each survey, 15 bowl traps were placed at a study plot before 0900 h and collected after 1500 h. Traps were placed on level ground in an alternating sequence of colors, deployed in a roughly linear transects that approximately bisects the plot via its center. Traps were placed 5-10 m apart from one another and at least 1 m from the canopy of large shrubs to avoid being shaded. Concurrently with the bee sampling, the identities and relative abundances of entomophilous plant species occurring in each plot in each year were documented. In 2015, the number of individuals of each plant species that was blooming during each survey was estimated; in 2016, the number of flowers (or capitula, for Asteraceae) of each plant species that was blooming during each survey was estimated. Because many key plant species in the study system are patchily distributed and because the thick growth of large, woody shrubs prohibited the use of random linear transects at many of the study plots, documenting blooming plants was achieved by walking through pre-planned paths that allowed the observer’s field of view to cover the entirety of the study plot.
description: This dataset was collected by Keng-Lou James Hung during his PhD dissertation at UC San Diego. The original intent of this data collection effort was to examine whether patterns of diversity in native bees collected via passive bowl trapping would be predictive of the structure of plant-pollinator interaction networks. For data on plant-pollinator interaction networks collected contemporaneously with this dataset in the same study plots, see "Plant-pollinator interaction networks in coastal sage scrub reserves and fragments in San Diego" (https://doi.org/10.6075/J0DZ067F). Since this dataset was collected immediately following the 2014 severe drought event in California, it also allows for comparisons with data collected immediately prior to the drought using the same standardized sampling methods. For such data collected in 2011-2012, see "Data from: Urbanization-induced habitat fragmentation erodes multiple components of temporal diversity in a Southern California native bee assemblage" (https://doi.org/10.6075/J000001W). The data file contains three tables. The first table lists the study plots used in the study. The second table lists the bee specimens collected in the study. The third table lists the entomophilous plant species in the study plots that were recorded as being in bloom during the study.