Distribution and diversity of planktonic ciliates: Patterns and processes

2009 2009

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Abstract (summary)

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.

Indexing (details)

Biological oceanography
0329: Ecology
0410: Microbiology
0416: Biological oceanography
Identifier / keyword
Biological sciences; Choreotrichia; Ciliate; Culture independent; Marine plankton; Microbial diversity; Oligotrichia
Distribution and diversity of planktonic ciliates: Patterns and processes
Doherty, Mary
Number of pages
Publication year
Degree date
School code
DAI-B 70/12, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
Katz, Laura A.
Committee member
Dorit, Rob; McManus, George B.; Normark, Benjamin B.
University of Massachusetts Amherst
Organismic & Evolutionary Biology
University location
United States -- Massachusetts
Source type
Dissertations & Theses
Document type
Dissertation/thesis number
ProQuest document ID
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
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