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Abstract Detail


McAllister, Chrissy [1], Clewell, Sarah [2], Bookout, Bess [2], Biang, Kathrines [2], McKain, Michael [3], Kellogg, Elizabeth [4].

Diaspore diversity and climate variation in the grass tribe Andropogoneae.

Species in the genera Diheteropogon, Andropogon, Schizachyrium, and Hyparrhenia are ecological dominants in grasslands in warm areas of the Old and New Worlds. Together they make up a clade, along with several smaller genera, of about 250 species in the grass tribe Andropogoneae; the formal name of the clade is Andropogoninae but it has also been called the DASH clade, an acronym for the included genera. The species vary considerably in numerous morphological characteristics (e.g. plant height, leaf and floral morphology). However, like all Andropogoneae, members of the DASH clade have paired spikelets, one sessile and one pedicellate. Several of the morphological characteristics of the spikelet pairs may be adaptations for dispersal. For example, in most species, the sessile spikelet bears a twisted geniculate awn. Many species also have spikelets covered with dense, downy hairs. The broad geographic range of the clade includes extremes of temperature and precipitation, but whether any of these potentially dispersal-related morphological features correlate with ecological variables is unknown. In this study we have combined image-based analysis of herbarium specimens, GIS-based analysis of the environment, and a molecular phylogeny of whole chloroplast genomes in a study with near-complete species sampling (ca. 200 of 250 species). The phylogeny is robust and shows that Andropogon is polyphyletic, Diheteropogon is monophyletic, and Schizachyrium and Hyparrhenia may be paraphyletic. Preliminary principal components analyses suggest that awnless species occur primarily in wetter sites with less seasonal variability in precipitation. We found no correlation between awn length and any of the climatic variables. Preliminary phylogenetic least squares (PGLS) analysis indicates awn length and size of the sessile spikelet are not correlated with each other, indicating that they are evolving in distinct ways and in response to different selective pressures. When corrected for phylogeny, awn length correlates weakly with maximum annual temperature and possibly with fire frequency. Sessile spikelet size was negatively correlated with temperature, and positively with an index of soil nutrient availability. Further analysis of phylogenetically-informed relationships between morphological variation and climate variation are ongoing.

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1 - 1 Maybeck Place, Principia College, Elsah, IL, 62028, USA
2 - Principia College, 1 Maybeck Place, Principia College, Elsah, Illinois, 62028, United States
3 - Donald Danforth Plant Science Center, Plant Biology, 975 N. Warson Rd., St. Louis, MO, 63132, USA
4 - Donald Danforth Plant Science Center, Department Of Biology, 975 North Warson Road, St. Louis, MO, 63132, USA

morphological evolution

Presentation Type: Poster
Session: P, Systematics
Location: Exhibit Hall/Omni Hotel
Date: Monday, June 26th, 2017
Time: 5:30 PM This poster will be presented at 6:15 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PSY014
Abstract ID:432
Candidate for Awards:None

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