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1 August 2007 Small-Scale Spatial Pattern of Web-Building Spiders (Araneae) in Alfalfa: Relationship to Disturbance from Cutting, Prey Availability, and Intraguild Interactions
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Abstract

Understanding the development of spatial patterns in generalist predators will improve our ability to incorporate them into biological control programs. We studied the small-scale spatial patterns of spider webs in alfalfa by analyzing the relationship between web locations over distances ranging from 4 to 66 cm. Using a coordinate-based spatial statistic (O-ring) and assuming a heterogeneous distribution of suitable web sites, we analyzed the impact of cutting and changes in spider abundance on web distribution. We analyzed the influence of small-scale variation in prey availability by comparing web distributions to the pattern of sticky-trap captures of Aphididae and Diptera described by a count-based spatial statistic (SADIE). Cutting of alfalfa reduced the overall density of web-building spiders but had no immediate impact on the spatial distribution of their webs. Availability of aphids was highest before the alfalfa was cut and was clumped at a scale of 66 cm. Spider webs, however, were not clumped at any scale or date. In contrast, webs were regularly distributed at smaller distances (<20 cm) immediately before and after cutting. Because cursorial and web-building spiders were most active during this period, we hypothesize that the development of small-scale regularity in web locations was driven by intraguild interactions. Our results suggest that intraguild interactions contribute to the development of small-scale spatial patterns of spider webs in alfalfa. Variation in prey availability may have more of an influence on web distribution in crops with a different vegetation structure or if patterns are studied at larger spatial scales.

Klaus Birkhofer, Stefan Scheu, and David H. Wise "Small-Scale Spatial Pattern of Web-Building Spiders (Araneae) in Alfalfa: Relationship to Disturbance from Cutting, Prey Availability, and Intraguild Interactions," Environmental Entomology 36(4), 801-810, (1 August 2007). https://doi.org/10.1603/0046-225X(2007)36[801:SSPOWS]2.0.CO;2
Received: 21 February 2007; Accepted: 7 May 2007; Published: 1 August 2007
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