Forest fragmentation causes diverse changes to natural communities. Changes in spider communities' species diversity provide tools to understand the effects of area and isolation in a fragmented landscape. Bottomland Hardwood forest provides an excellent opportunity to study fragmentation because it has undergone profound loss and subdivision The present study was carried out in 11 fragments of three size classes, the small ranging from 2.7 to 91 ha, medium from 1,042 to 5,294 ha, and large from 32,348 to more than 460,000 ha. The forest remnants were located inside and around New Orleans, Louisiana. A rapid assessment methodology was used to measure the biological diversity of spiders in the fragments. A total of 3,538 adult female spiders in 127 morphospecies were collected in 274 sampling units. The expected number of species for Bottomland Harwood forest was calculated between 161 and 210 species using EstimateS software. Evaluation of the effects of Bottomland Forest fragmentation on the spider community demonstrated significant negative consequences of area reduction on spider species diversity. Not only did species richness decrease, but also species composition changed with decreased fragment size. Species composition was influenced by both population extirpations in small fragments and by the presence of spider species adapted to open areas moving inside a small forest remnant. Spider species composition inside small sized fragments differed from the species observed both in medium and large sized fragments Functional (guild) community relationships were also distorted by fragmentation. The dominance of some species of spiders was more pronounced in small and medium sized fragments. For example, large-bodied, orb-weaving spiders tended to decrease from, and small theridiids increased proportionately in the small fragments. Size of prey was also affected significantly for hymenopterans, dipterans, and homopterans, suggesting more complex effects of forest fragmentation. Another observation from the present study was the strong effect of the surrounding matrix on the diversity of species, exemplified by the unusually high diversity of a fragment surrounded by agricultural activities in comparison to others engulfed by urban development This study supported the advantages of using rapid assessment techniques in the evaluation of biological diversity and for the first time this technique was used in fragmented habitats. The use of non-parametric analysis to predict species richness provided consistent results for medium and large sized fragments and more variable results in the small ones as a consequence of the elevated proportion of singletons observed there / acase@tulane.edu
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_23651 |
| Date | January 2004 |
| Contributors | Valderrama-Ardila, Carlos Humberto (Author), Sherry, Thomas W (Thesis advisor) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Rights | Access requires a license to the Dissertations and Theses (ProQuest) database., Copyright is in accordance with U.S. Copyright law |
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