Sinn, Brandon , Freudenstein, John .
Analysis of Complex Floral Shape in Appalachian Asarum: A Journey without Landmarks.
There are 11 species and 3 varieties of Asarum (Aristolochiaceae) endemic to the Appalachian region. Interspecific relationships and species delimitation have long been a problem in this group. Species limits are largely based on macro-level floral characters, especially calyx tube morphology. Field observations and published descriptions reveal overlap in flower size between species. Calyx shape is the most often used species diagnostic used, but to date this has only been described qualitatively. Presence or absence of a mid-calyx ridge and the widest portion of the calyx tube are readily referred to in published species descriptions, however the presence and placement of a calyx ridge can be variable within species. The characterization of ridges and curves of the calyx in Asarum poses a challenge for meaningful analysis by traditional morphometric methods due to a paucity of diagnosable landmarks. Radial Fourier Analysis (RDA) was used to characterize calyx shape of outlines created from photographed flowers. RDA works by iteratively testing the goodness of fit between radial shapes comprised of a specified range of curves with that of the analyzed outline. These returned fit coefficients form the spectrum for a given shape. Principle Components Analysis (PCA) was used to test for unique groupings of Fourier spectra. PCA identified groups consistent with some taxonomic boundaries in Asarum.The first three Principle Components (PCs) account for >95% of the observed variation. The elliptical nature of the calyx loads strongly on PC1 which explains 85% of the overall variation. Additional shapes, most notably 3 and 4 lobed objects, account for the remaining 15% of the variation. The narrow endemics A. contractum and A. rhombiformis form well separated groups, as do A. shuttleworthii, and A. arifolium. There is much overlap between the commonly misidentified A. virginicum and A. heterophyllum. Accessions identified to be the newly published Hexastylis sorriei bridge ordination space between (A. heterophyllum + A. virginicum) and A. minus. A. memmingeri, once separate from A. virginicum, is shown to be distinct. This work represents the first use of morphometric methods to quantitatively assess and categorize calyx shape in Asarum. These results provide direction for additional morphological and molecular analyses.
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1 - Ohio State University, Department of Evolution, Ecology, and Organismal Biology, 1315 Kinnear Rd, Columbus, OH, 43212, USA
2 - Ohio State University, MUSEUM OF BIOLOGICAL DIVERSITY, 1315 KINNEAR RD, COLUMBUS, OH, 43212-1157, USA
Radial Fourier Analysis
Presentation Type: Oral Paper:Papers for Sections
Location: Delaware B/Hyatt
Date: Wednesday, July 11th, 2012
Time: 4:30 PM