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Abstract Detail



Pteridological Section/AFS

Mchenry, Monique [1], Testo, Weston [1], Barrington, David [2].

Spore shape as a tool for the differentiation of diploid and tetraploid fern taxa with monolete spores.

The measurements of spore size that have contributed to inferences about ploidy in ferns have traditionally depended on length measurements. Though spore volume calculated from spore dimensions has been demonstrated to reflect ploidy better, it is rarely used. What is more, the relationship between spore shape and ploidy has never been investigated. We explored the relationship between spore shape and ploidy through an investigation of length and diameter of monolete spores from an array of homosporous ferns in the Eupolypods. We first gathered data on exospore length and diameter (perpendicular to the length in the plane of the laesura) for 51 species in five genera. These data revealed that spores of tetraploid species in the sample have significantly higher length-to-diameter ratios (l/d = 1.50, SD ± 0.10) than those of the sampled diploids (l/d = 1.34, SD ± 0.07). In all genera studied, spore length-to-diameter ratio was found to be a better predictor of ploidy level than the commonly used metric of spore length alone. Next we measured spore-shape change during growth from the end of meiosis to spore maturity in Dryopteris intermedia and its allotetraploid derivative D. campyloptera. Spores of both increased more than 5-fold in volume during this time; the increased volume of the tetraploid was added almost entirely through increase in length, yielding the higher length-to-diameter ratio. Finally, as a test case we explored spore shape in an array of polystichums from different elevations in the Andes with limited documentation of ploidy. With the partition of species into diploid and tetraploid groups based on shape we revealed an underlying strong pattern of larger spore size at higher elevations, consistent with the pattern of larger size in smaller habitat islands previously reported.

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1 - University of Vermont, Plant Biology, 111 Jeffords Hall, 63 Carrigan Drive, Burlington, VT, 05405, USA
2 - University of Vermont, Plant Biology, 111 Jeffords Hall, 63 Carrigan Dr., University of Vermont, Burlington, Vermont, 05405, United States

Keywords:
spore shape
Polyploidy
fern
spore development.

Presentation Type: Oral Paper:Papers for Sections
Session: 34
Location: Melrose/Riverside Hilton
Date: Tuesday, July 30th, 2013
Time: 2:30 PM
Number: 34005
Abstract ID:468
Candidate for Awards:None


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