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Abstract Detail


Ladner, Jamie [1], Mayfield, Mark H. [1], Prather, L. Alan [2], Ferguson, Carolyn J. [1].

Polyploidy and diversity in Phlox: genome size variation in tetraploid P. nana Nutt. (Polemoniaceae).

Polyploidy is prominent in the genus Phlox, and some species exhibit variation in ploidy levels, or cytotypic variation. Phlox nana is of particular interest because diploid, tetraploid and hexaploid populations occur across parts of the species distribution in the southwestern United States. A recent study highlighted two areas wherein inference of cytotypic patterns was challenging: the Davis Mountains region of West Texas, and a site on the Pecos Plains of New Mexico (“Caprock”). Study of plants in these areas yielded unusual genome size measurements that did not enable clear inference of ploidy levels, potentially due to presence of multiple ploidy levels, variation in genome size at homoploid levels, and/or presence of B chromosomes. This study intensively sampled plants in spring of 2015 and 2016, including nine sites in the Davis Mountains (generally five individuals per population) and 13 individuals at the Caprock site. Flow cytometry was used to estimate the genome size of samples, and mitotic chromosome counts were conducted on root tips from eight of the 10 sites. Flow cytometry indicated that populations are uniform for ploidy level. Both diploid (2n=14; ca. 9 pg) and tetraploid (2n=28; ca. 19pg) populations occur in the Davis Mountains, sometimes in close geographic proximity, and Caprock individuals are tetraploid (2n=28; ca. 16pg). The tetraploid genome size is larger in the Davis Mountains than in plants from Caprock. B chromosomes were detected in one or more chromosome counts from each area; however, most chromosome counts from the Davis Mountains did not reveal presence of B chromosomes, suggesting the larger genome size in the region is due to other factors. The importance of linking flow cytometry data to actual chromosome counts for a given study species is well established, and this approach enables appropriate and rapid inference of ploidy levels across natural populations. Our study, however, also highlights that genome size measurements for plants of a single ploidy level may vary across the distribution of a species. Overall, this study clarifies patterns of cytotypic diversity in P. nana, and contributes to a framework for ongoing study examining genetic, ecological, and morphological diversity relative to polyploidy in this system.

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1 - Kansas State University, Herbarium and Division of Biology, Ackert Hall, Manhattan, KS, 66506, USA
2 - Michigan State University, PLANT BIOLOGY, Plant Biology Laboratories, 612 Wilson Rd, Rm 48, East Lansing, MI, 48824-1312, USA
3 - Kansas State University, Herbarium and Division of Biology, Ackert Hall, Manhattan, KS, 66506, USA

chromosome number
flow cytometry

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 5:30 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: PSY019
Abstract ID:505
Candidate for Awards:None

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