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Abstract Detail

Phycological Section

Theriot, Edward [1], Coleman, A. [2], Goertzen, L. [3], Alverson, A. [4].

Species boundaries and nuclear rDNA ITS intragenomic polymorphism in recently evolved freshwater centric diatoms.

The diatom genera Cyclotella, Cyclostephanos and Stephanodiscus (Order Thalassiosirales) often dominate the phytoplankton assemblage of lakes and rivers around the world. They are important indicators of aquatic ecological conditions. Their taxonomy, however, remains in flux. The tools of molecular systematics have only recently been applied to these problems and previous studies have suggested that molecular data may provide greater resolution than morphological data. However, there remains the possibility that very recent radiations may not be tracked by commonly used approaches. We present such a case in which species distinguishable by morphology and/or physiology are not distinguishable by sequences obtained from the nucleus encoded ITS region, in part because intragenomic polymorphism swamps intraspecific differences. Several of the species appear to have diverged during the very latest Pleistocene and early Holocene, suggesting that much of the modern plankton diatom flora may have evolved very recently.

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1 - University of Texas at Austin, Texas Natural Science Center, 2400 Trinity Street, Austin, TX, 78705, USA
2 - Brown University, 69 Brown Street, Providence, RI, 02912, USA
3 - Auburn University, Biological Sciences, 101 Life Sciences Building, Auburn, AL, 36849
4 - Indiana University, Department of Biology, 1001 East Third Street, Bloomington, IN, 47405-3700, USA

intragenomic polymorphism
species circumscription

Presentation Type: Oral Paper:Papers for Sections
Session: CP35
Location: Lake Michigan/Hilton
Date: Tuesday, July 10th, 2007
Time: 4:45 PM
Number: CP35003
Abstract ID:1954

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