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Abundance and community composition of arboreal spiders : the relative importance of habitat structure, prey availability and competition

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dc.contributor.advisor Lattin, John D.
dc.contributor.advisor Ross, Darrell W.
dc.creator Halaj, Juraj
dc.date.accessioned 2012-10-17T21:26:25Z
dc.date.available 2012-10-17T21:26:25Z
dc.date.copyright 1996-05-06
dc.date.issued 1996-05-06
dc.identifier.uri http://hdl.handle.net/1957/34526
dc.description Graduation date: 1996 en_US
dc.description.abstract This work examined the importance of structural complexity of habitat, availability of prey, and competition with ants as factors influencing the abundance and community composition of arboreal spiders in western Oregon. In 1993, I compared the spider communities of several host-tree species which have different branch structure. I also assessed the importance of several habitat variables as predictors of spider abundance and diversity on and among individual tree species. The greatest abundance and species richness of spiders per 1-m-long branch tips were found on structurally more complex tree species, including Douglas-fir, Pseudotsuga menziesii (Mirbel) Franco and noble fir, Abies procera Rehder. Spider densities, species richness and diversity positively correlated with the amount of foliage, branch twigs and prey densities on individual tree species. The amount of branch twigs alone explained almost 70% of the variation in the total spider abundance across five tree species. In 1994, I experimentally tested the importance of needle density and branching complexity of Douglas-fir branches on the abundance and community structure of spiders and their potential prey organisms. This was accomplished by either removing needles, by thinning branches or by tying branches. Tying branches resulted in a significant increase in the abundance of spiders and their prey. Densities of spiders and their prey were reduced by removal of needles and thinning. The spider community of needle-sparse branches was dominated by orb weavers (Araneidae), whereas tied branches were preferably colonized by sheet-web weavers (Linyphiidae and Micryphantidae), and nocturnal hunting spiders (Anyphaeilidae and Clubionidae). Spider species richness and diversity increased in structurally more complex habitats. In 1994 and 1995, I excluded foraging Camponotus spp. ants from canopies of sapling Douglas-fir. Biomass of potential prey organisms, dominated by Psocoptera, increased significantly by 1.9 to 2.4-fold on the foliage following ant exclusion. Hunting spiders, dominated by the Salticidae, increased significantly by 1.5 to 1.8-fold in trees without ants in the late summer. The exclusion of ants did not affect the abundance of web-building spiders. Documented aggressive behavior of aphid-tending ants suggests interference competition between hunting spiders and ants. en_US
dc.language.iso en_US en_US
dc.subject.lcsh Spiders -- Ecology -- Oregon en_US
dc.title Abundance and community composition of arboreal spiders : the relative importance of habitat structure, prey availability and competition en_US
dc.type Thesis/Dissertation en_US
dc.degree.name Doctor of Philosophy (Ph. D.) in Entomology en_US
dc.degree.level Doctoral en_US
dc.degree.discipline Science en_US
dc.degree.grantor Oregon State University en_US
dc.contributor.committeemember Perry, David A.
dc.contributor.committeemember Boucot, Arthur J.
dc.description.digitization File scanned at 300 ppi (Monochrome) using Capture Perfect 3.0 on a Canon DR-9050C in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR. en_US
dc.description.peerreview no en_us

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