Ballard Jr, Harvey .
Delineating taxon boundaries in two confusing species complexes of Mesoamerican Hybanthus (Violaceae).
Two confusing species complexes with morphologically overlapping taxa reside under Hybanthus. Neither has been adequately studied to date but collectively represent a considerable percentage of Mesoamerican hybanthoid specimens in herbaria. To clarify taxonomic boundaries in each complex, we used traditional herbarium methods, phenetic analysis and pollen stainability as evidence for decisions. The Hybanthus thiemei complex, with long filiform pedicels and petioles and strongly zygomorphic corollas, consists of H. longipes and H. thiemei, putatively differing in pedicel length and capsule pubescence. After assigning specimens to glabrous versus puberulent capsules, features of stem, petiole and leaf blade, and mature flowers, were measured and subjected to canonical variates analysis. The capsule pubescence phenotypes were fully intergradient, with highly variable petiole and pedicel length, and no feature besides capsule pubescence provided separation, suggesting that H. longipes should be synonymized under H. thiemei. The Hybanthus elatus complex, with beaked capsules and elliptical to lanceolate leaves, consists of H. elatus in western Guatemala, H. potosinus in northern Mexico, H. verbenaceus in central and southern Mexico, and H. brevis in Chiapas and western Guatemala. The last has mostly been ignored since description or synonymized under H. elatus. Distinctive pubescence type and distribution were used to assign specimens to taxa. Canonical variates analysis largely separated specimens based on leaf shape and blade margin, and it consistently placed H. brevis between specimens of lower-elevation H. verbenaceus and higher-elevation H.elatus. Analysis of floral and fruit features further distinguished all four taxa. Pollen stainability was high (>86%) in H. elatus, H. potosinus and H.verbenaceus but statistically lower (52-77%) in H. brevis. Morphological intermediacy, intermediate montane slope position, monospecific populations, and depressed fertility but substantial seed production raise the possibility that H. brevis is a partially stabilized hybrid derivative of H. elatus and H. verbenaceus.
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1 - Ohio University, ENVIR & PLANT BIOLOGY-PORTER H, 315 Porter Hall, Athens, OH, 45701-2979, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Lindell C/Chase Park Plaza
Date: Tuesday, July 12th, 2011
Time: 9:15 AM