Razifard, Hamid , Les, Donald , Peredo , Elena Lopez , King, Ursula .
Preliminary systematic studies of Elatine L. (Elatinaceae).
Elatine L. (Elatinaceae Dumortier; waterworts) is a cosmopolitan genus of about 25 aquatic plant species in the order Malpighiales. The genus is interesting taxonomically for two main reasons. First, no systematic studies have been made on the genus using recently available molecular techniques. Second, two species from this genus (E. triandra Schkhuhr and E. ambigua Wight) have been reported as invasive in recent decades. There also are indications of polyploidy in the invasive species, which make the genus particularly interesting from both ecological and systematic standpoints. Botanists disagree on the delimitation of several Elatine species. For example, descriptions provided for E. americana and E. minima in various floras often can be applied to either species. This problem results in a high degree of overlap for morphological characters used in such regional floristic treatments. In order to better distinguish each Elatine species, we assembled a data matrix of 37 morphological characters scored from more than 20 specimens per species. We analyzed the data using principle component analysis to search for potential discontinuities among taxa. In addition, we obtained new morphological characters using scanning electron microscopy (SEM) to examine the fine structure of Elatine seeds. Seed analysis using SEM indicated that several differences in seed surface morphology were potentially useful taxonomically, i.e.: length to width ratio, degree of seed curvature, and number of seed surface locules. These characters are promising for clarifying the taxonomy and systematic relationships of the genus at or above the species level. We also obtained the sequences of nuclear (nrITS) and chloroplast gene regions (matK and rbcL) for seven and two Elatine species respectively. We used ITS sequences to construct a preliminary phylogenetic tree for the genus using maximum likelihood. Some populations thought to belong the same species, e.g. those of E. triandra and E. minima, did not resolve as clades. This result could reflect misidentified specimens or hybridization. To address such questions, we combined the results of molecular phylogeny construction, SEM analysis, and morphological survey to provide better insights on delimitation of and relationships among Elatine species.
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1 - University Of Connecticut, Department Of Ecology & Evolutionary Biology, 75 N. Eagleville Road, Unit 3043, Storrs, CT, 06269-3043, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Franklin B/Hyatt
Date: Tuesday, July 10th, 2012
Time: 9:45 AM