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Abstract Detail


Wettewa, Eranga [1], Wallace, Lisa [1].

Floral micromorphology across Platanthera section Limnorchis (Orchidaceae).

Platanthera (Orchidaceae) is one of the largest genera of temperate orchids, with more than 200 species occurring in north temperate areas. Platanthera section Limnorchis is monophyletic and has long been recognized to be morphologically distinct from other Platanthera in North America. However, the recognition of several new species recently and morphological similarity of U.S. species with congenerics in Mexico and Asia have hindered a thorough understanding of species diversity and phylogenetic relationships in Limnorchis. Incorporating ultra structural features into a phylogentic analysis would enable understanding important fitness traits leading to evolutionary diversifications Floral morphological features like length of the spur and column structure is important as they can strongly influence reproductive isolation and fitness through cryptic variation. Although a trend in evolution from shorter to longer nectar spurs in Platanthera has been noted, my preliminary phylogenetic analyses suggest spur length is evolutionarily labile in Limnorchis. In this project, we developed six novel exon-primed-intron-crossing (EPIC) markers to estimate the phylogeny of section Limnorchis. Preliminary results are presented to test two hypotheses 1) Section Limnorchis is monophyletic relative to other Platanthera species, 2) Species diagnosed by morphological characters are genetically divergent and represent distinct evolutionary lineages. A major part of this project covered collecting micromorphological data on the flowers across section Limnorchis to determine whether variation mirrors that seen in macromorphological traits of flowers. The data collected from SEM images allowed to study the micromorphology, mainly in spur, column, pollinia and labellum. Variations were observed in the spur and the labellum within the section. Compared to the spur morphology in Orchidaceae, members in section Limnorchis showed consistent patterns in striations and papillate cell layer inside the spur. These results will assist in resolving the section boundaries and revising the taxonomy of section Limnorchis, studying the evolution of flower morphology, and testing biogeographic hypotheses of diversification across North America.

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1 - Mississippi State University, Department of Biological Sciences, PO Box GY, Starkville, MISSISSIPPI, 39762, United States

Floral micromorphology

Presentation Type: Oral Paper
Session: 14, Systematics I: Basal Dicots, Monocots & Rosids
Location: Sundance 1/Omni Hotel
Date: Monday, June 26th, 2017
Time: 2:30 PM
Number: 14005
Abstract ID:499
Candidate for Awards:George R. Cooley Award

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