Influence of Savannization and Brush Invasion on Spider Diversity

Project Number: 
Project Duration: 
44 Months
May 1, 1999 to December 31, 2002
Institution of Principle Investigator while on this project: 
Ben-Gurion University of the Negev

Investigators (most current known information)

Ecologist, Ben-Gurion University of the Negev, Mitrani Center for Desert Ecology, Jacob Blaustein Institute for Desert Research, Sede Boker Campus 84993, ISRAEL
TEL: +972-8-552-650, FAX: +972-8-557-829, Email:
Science Specialist, Department of Entomology, Plant Pathology & Weed Science, New Mexico State University, MSC 3BE, Box 30003, Las Cruces NM 88003
TEL: +1-575-646-2900, FAX: +1-575-646-8087, Email:

Proposal Abstract

The aim of the study was to compare two arid systems undergoing anthropogenic changes, namely an increase in cover of shrubs and trees. In one system, trees were added to increase landscape diversification, while in the other system, trees and shrubs are encroaching on an arid grassland habitat. We conducted parallel studies of the direct and indirect effects of the increase in cover of trees and shrubs on the spider community by comparing spider densities and species richness in altered and natural habitats at two sites. At Sayeret Shaked Park in Israel, we compared "savannized" and natural scrubland, while at the Jornada, Doņa Ana County, New Mexico, U.S.A. we compared shrub-encroached and natural scrubland. In the Sayeret Shaked (Israel) project, we found that the semiarid scrubland contains different patch types with communities of different species, but that the community structure of the patches is similar. Thus large-scale environmental factors typical of the area as a whole influence coarse-grained community structure, while small-scale differences between patch types result in the specialization of species to different patch types. The second part of the study specifically addressing the influence of trees is being analyzed. Similar preliminary results were obtained in the Jornada (New Mexico), where mesquite invasion had less effect on spider diversity overall, but species composition and community structure differed significantly among habitat types.


Articles in Journals

Pekar S. and Y. Lubin. 2004. "Habitats and interspecific associations of zodariid spiders in the Negev (Araneae Zodariidae)." Vol 49. Israel Journal of Zoology 50(1):123-123.

Whitehouse M.E.A,, E. Shochat and M. Shachak. 2002. "The influence of scale and patchiness on spider diversity in a semi-arid environment." Ecography 25(4):395-404.


Support for this project came from the USDA Cooperative State Research, Education, and Extension Service