Date of Award:

1978

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Biology Ecology

Advisor/Chair:

James A. MacMahon

Abstract

The relationships between vegetation architecture and spider community attributes were examined in a big sage (Artemisia tridentata) community. Spiders were separated into guilds using similarities of species' hunting behavior. Shrub architecture was experimentally manipulated in the field by either clipping 50% of a shrub's foliage to decrease foliage density or tying together a shrub's branches to increase foliage density.

Temporal patterns of spider species density, diversity (H') and evenness (J') showed midsummer peaks in both 1974 and 1975. Seasonal spider guild trends reflected the temporal prominence of a member species or genus. These temporally abundant species appeared to play a major functional role in this community.

Shrub perturbations resulted in changes in spider species and guild densities. Spider species and guild density in the tied shrubs were significantly higher than that in the clipped or control shrubs sampled. Spider species diversity, density and guild density were also positively correlated with indicators of shrub volume and shrub foliage diversity. This suggests that structurally more complex shrubs (tied) can support greater spider species densities and diversity.

Spider guild densities and IV's were significantly altered by changes of shrub architecture. The observed guild distribution were in agreement with known hunting behavior and life history data of the member species.

The data suggest that architectural properties of habitat may be an important determinant of predatory invertebrate species diversity and distribution. Guild analysis may be useful in examining the roles of species groups in community studies.

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