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Graduate Program in Organismic and Evolutionary Biology
University of Massachusetts-Amherst
(413) 585-3750Education:
Ph.D. Candidate, Program in Organismic and Evolutionary Biology University of Massachusetts, Amherst, MA 2005-present
M.A. Biological Sciences, Smith College, Northampton, MA 2005
M.Ed. Education 180 Days in Springfield Project, University of Massachusetts, Amherst, MA 1998
B.A. Biological Sciences, Smith College Northampton, MA 1990
Research Interests:
Biogeography of Planktonic Ciliates
Ciliates from the clades Choreotrichia and Oligotrichia are a vital part of marine planktonic food webs. Because of their size, they serve as a critical trophic link between the nano- and picoplankton, and larger metazoan organisms. Understanding how these ciliates are distributed across time and space has been limited to a few taxa with easily recognized morphology. To gain a better understanding of the diversity and distribution of these two clades in New England coastal waters, I am applying molecular tools to characterize their genetic diversity across time and space. By designing primers specific to these two groups, and generating clone libraries for six collections, I have found: (1) high levels of genetic diversity within the Oligotrichia relative to morphological assessments of the same samples (2) different assemblages of haplotypes at each sampling location and time and (3) comparable estimates of diversity within the Choreotrichia, using both morphology and molecules.
Sediments as a ‘Seed Bank’ of Ciliate Diversity
Because many ciliates undergo a cycle of encystment and excystment based on environmental conditions, one hypothesis I am testing is whether the variation in haplotype assemblages across planktonic samples is really a subset of the cyst diversity in the underlying sediments. To test this hypothesis, I am using a DNA fingerprinting method known as denaturing gradient gel electrophoresis (DGGE) for Choreotrichia and Oligotrichia within sediment and planktonic samples. Clone library data suggest that the diversity within the sediments has little overlap with genetic diversity in the water column from the same collections.
Ecological Determinants of Ciliate Diversity
We found a much higher level of genetic diversity in the genus Strombidium (Oligotrichia) that we would have predicted based on morphological studies or on the worldwide estimate of morphospecies within this clade. If the genetic diversity we obtained is reflective of species diversity, the number of haplotypes we obtained in the Strombidium clade may indicate high levels ecological complexity within marine microenvironments, where many similar species are able to coexist by fine-scale partitioning of niches. Alternatively, these data may reflect high levels of standing genetic variation within a small number of species. Data on other planktonic ciliates within these subclasses are not consistent with this second assertion (Katz et al. 2005), as there are extremely low levels of genetic variation (<0.5%) in Laboea strobila populations sampled over space and time. I am interested in testing the hypothesis that diversity is due to ecological differentiation. To do this, I am intensively sampling genetic communities relative to fine scale changes in environment to determine the strength of correlation between haplotypes and ecology.
Recent Publications :
Costas, B, G. McManus, M. Doherty and L.A. Katz. In press. Use of species-specific primers and PCR to measure the distributions of planktonic ciliates in coastal waters. Limnol. Ocean: Methods.
