Effects of fragmentation on a distinctive coastal sage scrub bee fauna revealed through incidental captures by pitfall traps
Recent reports of pollinator declines have revealed a need to better document how anthropogenic disturbances and biogeography jointly influence wild pollinator communities. Here, we examine the effects of urbanization-induced habitat fragmentation on the native bee fauna inhabiting coastal sage scrub habitats of San Diego County, California, USA, a hotspot of bee biodiversity. Pitfall trapping in natural reserves and scrub habitat fragments yielded 70 native bee species or morphospecies, and revealed that bee species richness was lower in fragments than in reserves. However, fragments and reserves harbored bee assemblages similar in relative abundance, evenness, and community composition. Our samples yielded multiple species that are poorly represented in four of the leading institutions with collections of native bees from the southwestern United States, as well as 16 species represented only by specimen records from outside of San Diego County. Our results highlight the importance of continued efforts to document bee assemblages in under-studied regions with respect to their faunal distribution and basic taxonomy, as well as how they are impacted by anthropogenic disturbances such as habitat fragmentation. We also discuss the value of analyzing vouchered pitfall samples for non-target taxa captured incidentally.
KeywordsAnthophila Pollinators By-catch Habitat fragmentation Museum records
We gratefully acknowledge the late G. I. Stage for identifying Hesperapis. We thank E. Glassberg for laboratory assistance. We are also grateful for the helpful comments of two anonymous reviewers. This project was funded by National Science Foundation (NSF) award DEB-9981758 to D. T. Bolger and an REU supplement to NSF award DEB-0743535 to R. E. Irwin. Bee specimen records consulted were captured with funding from Robert G. Goelet, NSF award DBI-0956388 to J. S. Ascher, and NSF award DBI-0956340 to D. Yanega. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.
Conflict of interest
The authors declare no conflicts of interest.
- Buchholz S, Jess AM, Hertenstein F, Schirmel J (2003) Patterns in pitfall captures of millipedes (Diplopoda: Polydesmida: Paradoxosomatidae) at coastal heathland sites in Tasmania. The Australian Zoologist 32:431–438Google Scholar
- Danforth BN (1996) Phylogenetic analysis and taxonomic revision of the Perdita subgenera Macrotera, Macroteropsis, Macroterella and Cockerellula (Hymenoptera: Andrenidae). The University of Kansas Science Bulletin 55:635–692Google Scholar
- Krombein KV, Hurd PD, Smith DR, Burks BD (1979) Catalog of hymenoptera in America North of Mexico. Smithsonian Institution Press, WashingtonGoogle Scholar
- Mayer C, Adler L, Armbruster WS, Dafni A, Eardley C, Huang SQ, Kevan PG, Ollerton J, Packer L, Ssymank A, Stout JC, Potts SG (2011) Pollination ecology in the 21st century: key questions for future research. Journal of Pollination Ecology 3:8–23Google Scholar
- Moldenke AR, Neff JL (1974) Studies on pollination ecology and species diversity of natural California plant communities. In: International Biological Programme Technical Report, pp 74–14Google Scholar
- National Academy of Sciences—National Research Council (2007) Status of pollinators in North America. National Academies Press, Washington, p 307Google Scholar
- Oksanen J, Blanchet FG, Kindt R, Legendre P, Minchin PR, O’Hara RB, Simpson GL, Solymos P, Stevens MHH, Wagner H (2013) VEGAN: community ecology package. R package version 2.0-10. http://CRAN.R-project.org/package=vegan
- Pickering J, Smith K, Cotter G, Simpson A, Magill R, McNierney E (2006) Global Mapper. In: International Biogeography Society, news report, March, 2006. www.discoverlife.org/pa/or/polistes/fe/2006ibs.html
- Rebman JP, Simpson MG (2014) Checklist of the vascular plants of San Diego County, 5th edn. San Diego Natural History Museum, San DiegoGoogle Scholar
- Shinn AF (1967) A revision of the bee genes Calliopsis and the biology and ecology of C. andreniformis (Hymenoptera: Andrenidae). The University of Kansas Science Bulletin 46:753–936Google Scholar
- University of Kansas Biodiversity Institute: Snow Entomological Museum Collection (2014) http://www.discoverlife.org/. Accessed 03 Sept 2014
- US Department of Agriculture-ARS Bee Biology and Systematics Laboratory: Bee Biology and Systematics Laboratory (2014) http://www.discoverlife.org/. Accessed 03 Sept 2014
- Jensen DB, Torn M, Harte J (1990) In our own hands: a strategy for conserving biological diversity in California. In: California Policy Seminar Report, California Policy Seminar, University of California, Berkeley, Berkeley, CaliforniaGoogle Scholar