PS 27-150 - An Evaluation of Blooming Vegetation Variation on Crab Spider (Thomisidae) Abundance and Diversity in Eastern Oregon Grasslands

Tuesday, August 8, 2017
Exhibit Hall, Oregon Convention Center
Lauren J. Smith1, Lauren A. Smith2 and Sandra J. DeBano2, (1)Fisheries and Wildlife, Oregon State University, Corvallis, OR, (2)Fisheries and Wildlife, Oregon State University, Hermiston, OR

In Eastern Oregon, there have been a number of attempts to restore grassland environments. Grassland vegetation provides foraging habitat, breeding habitat and shelter for many types of invertebrates including spiders. Crab spiders (Thomisidae), for example, forage in grassland blooms that attract pollinators that the spiders predate on. The objective of this study was to evaluate the relationship between blooming grassland vegetation and spider abundance and diversity, with special attention to the Thomisidae family. Blooming vegetation and spider data were collected during the 2015 summer season (June-August). In this study, native, restored and degraded grassland habitats were compared at three different locations: The Nature Conservancy Boardman Grasslands and Zumwalt Prairie, and the Umatilla National Wildlife Refuge (UNWR). Blooming vegetation data were collected using transects and quadrats, and spiders were collected using pitfall traps.


Preliminary analyses indicate that the Boardman Grasslands has the highest abundance of Thomisidae (134 individuals), with a floral species richness of 16 species and 4,548 blooms. The Zumwalt Prairie has the highest floral species richness (50 species) and the highest total number of blooms (13,946 blooms). However, only 5 Thomisidae spiders have been identified in the samples from the Zumwalt prairie so far. The UNWR shows the lowest floral species richness (14 species) and the lowest total number of blooms (2,517 blooms) but has a moderate abundance of crab spiders (28 individuals). This study will provide more information about the effectiveness of grassland restoration on crab spider communities and beneficial invertebrate relationships by examining the association between crab spiders and blooming vegetation.