Abstract Detail



Systematics

Wallace, Lisa [1], Bailey, Nicholas [2], Wettewa, Eranga [3].

Comparative analysis of phylogeny and morphology in two polyploid orchids of Platanthera .

The ubiquity and importance of polyploidization in generating plant biodiversity is incredible. Studies documenting evolutionary origins and ecology of polyploid species provide a greater understanding of plant diversity and improved conservation of native biodiversity. Here, we characterized genetic and morphological variation in two morphologically similar polyploid orchid species, Platanthera huronensis and Platanthera hyperborea, with the intent of evaluating their evolutionary history with respect to one another and related diploid species. Platanthera hyperborea is considered to have a more restricted distribution than the P. huronensis, as it occurs only on Greenland and Iceland. Platanthera huronensis is widespread in mesic areas across Canada and the northern U.S. Given their morphological similarity, it has been hypothesized that these polyploid species evolved from the same parental species, and P. hyperborea persists on Greenland and Iceland where it is today the only species of Platanthera in these areas. In this project, we tested this hypothesis and evaluated the evolutionary history of the two forms using genetic and morphological data sets. We found that P. hyperborea contains numerous unique plastid types that were not detected in any other species tested. By contrast, P. huronensis plastid types resembled sequences from diploid species, P. dilatata and P. aquilonis, a relationship that has been confirmed in previous studies as well. At nuclear markers, Icelandic P. hyperborea samples most closely match those of P. dilatata, a widespread diploid species. By contrast, nuclear sequences from P. huronensis could be traced to both P. dilatata and P. aquilonis, also a diploid species with a widespread distribution. Morphological differences were noted between the P. huronensis and P. hyperborea, especially in flower color and lip shape, but intraspecific variation can impede identification when morphology alone is considered. For example, some individuals in the data set were sampled from North America and resemble P. hyperborea in morphology and P. huronensis in genetics. Based on these results, we conclude that the taxa are evolutionarily distinct and likely originated from morphologically similar parents. Platanthera huronensis contains much genetic and morphological variation, which likely reflects multiple polyploidization events across North America. Further characterization of the genetic and morphological diversity of P. huronensis across North America may reveal additional cryptic taxa worthy of taxonomic recognition.   


1 - Old Dominion University, Biological Sciences, Mills Godwin Building Rm. 110, Norfolk, VA, 23529, United States
2 - University of Memphis, Biological Sciences, Memphis, TN, 38152, USA
3 - Mississippi State University, Biological Sciences, P.O. Box GY, Mississippi State, MS, 39762, USA

Keywords:
Orchidaceae
Platanthera
Polyploidy
phylogenetic affinities
morphological variation.

Presentation Type: Oral Paper
Number:
Abstract ID:395
Candidate for Awards:None


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