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Influence of Spatiotemporal Variables in Structuring the Nematode Community of a Freshwater System

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abstract
ABSTRACT Kyle E. Luth INFLUENCE OF SPATIOTEMPORAL VARIABLES IN STRUCTURING THE NEMATODE COMMUNITY OF A FRESH WATER SYSTEM Thesis under the direction of Gerald W. Esch, Charles M. Allen Professor of Biology, Wake Forest University, Department of Biology The influence of spatiotemporal variables on the structure of the free-living nematode community in a eutrophic lake was studied. In particular, the influence of mo, season, and substratum type was considered. Substratum samples were collected, and nematodes were isolated, identified, and quantified. Prevalence, mean abundance, species richness, and the Shannon-Weiner diversity index (H’) were calculated for (1.) the overall system, (2.) each mo, (3.) each season, and (4.) each substratum type identified in the lake. A total of 2,349 nematodes representing 45 species (morphotypes) from 30 genera were observed, and the overall H’ was 2.5. The most commonly observed genera were Monhystera, Iotonchus, Dorylaimus, Semitobrilus, and Neotobrilus, in that order. Mean abundance for the entire system was 4.9± 0.5 nematodes per samples (mean ± SE). Results suggested that both mo and season influence nematode prevalence, and mo, season, and substratum type all impact the mean abundance of nematodes. Specifically, significant relationships were observed between nematode prevalence and both mo and season. Further, overall nematode mean abundance was significantly higher in April than other mo, lower in winter and higher in autumn than other seasons, and higher in mixed substratum than any other substrata. Finally, both species richness and diversity were highest in April, both were highest in spring, and the greatest species richness was observed in leaf substratum while the greatest diversity was observed in mud/algae substratum. The influence of the spatiotemporal factors, season and substratum type, on nematodes classified by feeding type was also considered. A total of 1,918 free-living nematodes were classified into 5 feeding types based on the type of food primarily consumed by each genus. When specific genus-level feeding habits were unknown, the dominant feeding type observed at the family-level was used. Five feeding types were observed in the current system: (1.) herbivores, (2.) bacterivores, (3.) unicellular eukaryote feeders, (4.) predators of animals, and (5.) omnivores. Specifically, 51.8% of the total nematodes recovered were classified as bacterivores, 21.3% were predators, 14.2% were omnivores, 11.3% were unicellular eukaryote feeders, and 1.3% were herbivores. Both season and substratum type appeared to influence the community composition in this system, with season showing the greatest influence on the predator feeding type, and substratum type showing the greatest influence on both predators and omnivores. Bacterivores were the most prevalent and the most abundant nematodes in nearly every season and substratum type considered. Finally, a second analysis was performed to investigate the influence of spatiotemporal factors (season and substratum type) on nematodes; instead of classifying nematodes by feeding type, a second method was used which groups worms by feeding method. A total of 1,928 free-living nematodes were classified into 5 groups based on the method utilized by each to acquire their food. Five feeding methods were observed in the current system: (1.) deposit feeder/swallower, (2.) epistrate feeder, (3.) chewer, (4.) suction feeder, and (5.) parasitic. In summary, 44.8% of the total nematodes recovered were classified as deposit feeders/swallowers, 34.6% were chewers, 15.6% were suction feeders, 6.4% were epistrate feeders, and 0.4% were parasites. Both season and substratum type appeared to influence the community composition of nematodes utilizing these various feeding methods in the system. Season had the greatest influence on the prevalence of deposit feeders and suction feeders, and on the mean abundance of all feeding methods, with the exception of deposit feeders. Substratum type had the greatest impact on the prevalence and mean abundance of suction feeders and chewers. Deposit feeders were dominant in nearly every season and every substratum type, and showed little fluctuation in both prevalence and mean abundance based on the spatiotemporal factors considered.
subject
Freshwater Ecology
Trophic Interactions
Feeding Type
Feeding Method
Shannon-Wiener Diversity
Richness
Eutrophic
Substratum Type
Monte Carlo
Buccal Morphology
Genus
Prevalence
Mean Abundance
Relative Abundance
Bacterivore
Deposit Feeder
contributor
Luth, Kyle (author)
Esch, Gerald (committee chair)
Eure, Herman (committee member)
McCauley, Anita (committee member)
Negovetich, Nicholas (committee member)
date
2010-05-07T18:14:05Z (accessioned)
2010-06-18T18:58:20Z (accessioned)
2010-05-07T18:14:05Z (available)
2010-06-18T18:58:20Z (available)
2010-05-07T18:14:05Z (issued)
degree
Biology (discipline)
identifier
http://hdl.handle.net/10339/14754 (uri)
language
en (iso)
publisher
Wake Forest University
rights
Release the entire work for access only to the Wake Forest University system for one year from the date below. After one year, release the entire work for access worldwide. (accessRights)
title
Influence of Spatiotemporal Variables in Structuring the Nematode Community of a Freshwater System
type
Thesis

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