Influence of habitat complexity on diversity and community structure of arboreal spiders in grassland-shrub systems

Knutson, Eric M., author
Charkowski, Amy, advisor
Aldridge, Cameron L., committee member
Trivedi, Pankaj, committee member
Hufbauer, Ruth, committee member
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Revealing the ecological drivers of species distribution is one of the central issues in ecology. The ecological niche concept recognizes that distribution of species is influenced by abiotic (e.g., temperature, landscape characteristics, and nutrients) and biotic (e.g., food availability) factors through both direct and indirect mechanisms. Many of these niche factors can influence the spatial position of plants in a landscape. Plant communities often determine the physical structure of the environment (microclimate, plant architecture) and therefore, have a considerable influence on the distribution of animal species, such as arthropods, and on local community structure. For instance, vegetation structure provides spatial complexity by creating microenvironments that may enable more interactions with other species that live on plants or allow resource partitioning. In grasslands, much of the arboreal habitat is in the form of shrubs, but the role and importance of shrubs in distribution and diversity of arthropods in grasslands is unknown. Spiders are a useful indicator for examining the role of shrubs in arthropod ecology because they are genetically and behaviorally diverse predators and prey that can be captured and counted with a single method. Spiders are a key component of invertebrate communities of grasslands and arboreal spiders of grasslands provide a unique ecological system to study habitat association and community assemblage. However, most spider studies in prairie ecosystems have focused on ground dwelling taxa or those associated with agroecosystems. Only limited data exist for shrub-dwelling species and few studies have compared arboreal spider occupancy across different grassland shrub species. I endeavored to understand this system in more detail by investigating how arboreal spider community structure responds to native shrub species, plant community composition and landscape complexity. Since landscape complexity can be evaluated at multiple scales, landscape characteristics can be significant predictors of presence and abundance for a variety of taxa. I collected and identified 3,053 specimens to family, genus or species level and found that presence of certain shrub species predicted spider species occurrence and suggested diversity community structure patterns. I found that habitat association to combinations on shrub species indicated habitat specific niche partitioning of arboreal spiders in two Colorado grassland systems. Because shrub species occurrence is largely dependent on elevation and moisture gradients, spider occupancy may also be tied to similar gradients correlated with these landscape factors. Changes in the topography of the sampling area affected the local plant communities of shrubs across a recognized elevational gradient, which correlated to habitat zones for arboreal spiders in the local area.
Includes bibliographical references.
2023 Spring.
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Embargo Expires: 05/26/2024
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