Off-campus UMass Amherst users: To download dissertations, please use the following link to log into our proxy server with your UMass Amherst user name and password.
Non-UMass Amherst users, please click the view more button below to purchase a copy of this dissertation from Proquest.
(Some titles may also be available free of charge in our Open Access Dissertation Collection, so please check there first.)
Distribution and diversity of planktonic ciliates: Patterns and processes
Abstract
The nature and extent of microbial biodiversity remain controversial with persistent debates over patterns of distributions (i.e. cosmopolitanism vs. endemism) and the processes that structure these patterns (neutrality vs. selection). I used culture-independent approaches to address these issues focusing on two groups of ciliates, the Oligotrichia (Spirotrichea) and Choreotrichea (Spirotrichea). To assess the diversity of these ciliates, I designed primers specific to SSU rDNA of ciliates within these clades, and investigated (1) geographic and temporal distributions along three coastal sites in the Northwest Atlantic; (2) the relationship between ciliate communities in the benthos and the plankton along the New England coast; and (3) diversity in ciliate communities across an environmental gradient at six stations in Long Island Sound spanning the frontal region that separates the fresher Connecticut River outflow plume from the open Sound. Each collection had its own distinct assemblage of rare and abundant ciliate haplotypes, and genealogical analyses of my samples combined with published sequences from identified morphospecies reveal that haplotype diversity at these sites is greatest within the genus Strombidium, in the Oligotrichia. Clustering of phylogenetic types indicates that benthic assemblages of oligotrichs and choreotrichs appear to be more like those from spatially distinct benthic communities than the ciliate communities sampled in the water above them. Neither ciliate diversity nor species composition showed any clear relationship to measured environmental parameters (temperature, salinity, accessory pigment composition, and chorophyll), although I observed that diversity decreased moving from nearshore to offshore. I find no strong fit of my communities to log series, geometric, or log normal distributions, though one of the 3 clusters is most consistent with a log series distribution. These analyses suggest that Oligotrich and Choreotrich communities in coastal environments may be distributed in a neutral manner. I investigated the effectiveness of molecular approaches in characterizing ciliate diversity in my samples. Estimates of diversity based on molecular markers are similar to estimates from morphological observations for Choreotrich ciliates, but much greater for Oligotrich ciliates. Sediment and plankton subsamples differed in their robustness to repeated subsampling. Sediment gave variable estimates of diversity while plankton subsamples produced consistent results.
Subject Area
Ecology|Microbiology|Biological oceanography
Recommended Citation
Doherty, Mary, "Distribution and diversity of planktonic ciliates: Patterns and processes" (2009). Doctoral Dissertations Available from Proquest. AAI3379953.
https://scholarworks.umass.edu/dissertations/AAI3379953