Doctor of Philosophy (PhD)
How do many species live in a certain place? How does species composition changes among habitats? And what mechanisms decide species distribution? These are fundamental questions in community ecology. I first investigated ant diversity in two coastal ecosystems (dunes and wetlands) in the northern Gulf of Mexico, and then used the distribution patterns to infer assembly processes that structure ant communities in coastal areas. Specifically, the following hypotheses are tested: (1) coastal systems support lower ant diversity due to the unsuitable environment; (2) species living near the seashore are a subset of those exist near inland; (3) deterministic processes are the dominant forces driving coastal ant communities. Forty-six and 22 ant species were found in dunes and wetlands, respectively. Although some ants were associated with certain habitats, no species could be considered a coastal specialist. Clementsian was the best model describing how ants change along environmental gradient in dunes. This indicated that each habitat supported a unique ant assemblage. In wetlands, most ants living in marshes could also be found in swamps, which is consistent with the nested pattern. Abiotic factors were the dominant forces that decide ant diversity and community structure. For example, wetlands are flooded most of the year, which eliminates the species nesting in the soil. In addition, the physical habitat structure of wetlands and dunes is simple because of the lower plant diversity. Niches are limited for ants to nest in and forage. Biotic factors, such as the influence of vegetation and species interactions, were weak because few mosaic patterns, pairwise co-occurrence, and correlation between ants and plants was detected in this study. The contribution of stochastic processes increased under the relatively benign environment (under bushes). In addition, this research suggested that ants can be used as biological indicators in coastal dunes and wetlands. Fragmentation, habitat restoration, oil pollution, and invasive species all influenced ant diversity and community structure. Although the responses of ant assemblages to disturbances were situation-dependent, the common effect was the invasion of the red imported fire ant, Solenopsis invicta Buren, following disturbances.
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Chen, Xuan, "Ant Diversity and Community Structure in Coastal Dunes and Wetlands" (2016). LSU Doctoral Dissertations. 2609.
Hooper-Bui, Linda M