Abstract Detail

Biogeography

Ramsey, Justin [1], Ramsey, Tara [2].

Climatic and edaphic adaptation of tetraploid wild yarrow (Achillea millefolium aggregate, Asteraceae) in the Black Hills and Great Plains, USA.

Polyploidy is widely acknowledged as a speciation mechanism, based on postzygotic reproductive barriers it confers. Polyploidy is also hypothesized to be a mechanism of adaptive evolution. Thus, polyploidization may alter anatomical and growth characteristics that coincidentally prove beneficial in certain habitats, or set the stage for cytotype divergence by reinforcement. Adaptive significance of polyploid genetics (multisomic inheritance, increased gene dosage and allele number per locus) are complicated and not easily generalized. Autopolyploids may exhibit high mean fitness (based on masking of deleterious alleles) and responses to selection, but theory suggests these tendencies depend on mode of gene action, inbreeding, and population interconnectivity. Because of their complexities, autopolyploids are avoided by ecological genetics studies. However, autopolyploids have desirable research features – wide geographic distribution, clonal reproduction, cross-ability of populations and varieties – and empirical work is needed to evaluate genetic factors affecting their ecological success. Here we report on the character and spatial scale of adaptation in tetraploid yarrow (Achillea borealis) along a 250 km transect in the Black Hills and Great Plains. Twenty-five study sites include shortgrass prairie, sagebrush flats, sand dunes, open pine forest, aspen forest, montane grassland and mountain summits (770-2,200 m elevation); transect populations are tetraploid and represent several taxonomic varieties (lanulosa, pacifica, alpicola, occidentalis). Yarrows on the transect differ markedly in size and architecture, with diminutive plants in low-elevation shortgrass prairie and mountain summits, and large plants in mid-elevation meadows and deciduous forests. Populations showed 10-fold leaf-area variation (population means 12.7-131.1 cm²) in 2015 while stem length and flower head number had 5- and 3-fold variation. Relative plant sizes in populations are consistent over time but replicated surveys indicated year and year x site effects. Garden experiments (2016-2018) suggest a genetic component for studied traits. Correlation in size-related traits of populations measured in the field vs. garden was highly significant (P<0.001, R²>0.800), and plants of low-elevation sites flowered ~3-6 weeks before others. Nonetheless, uniform growing conditions reveal diminutive size is more 'hard-wired' in shortgrass prairie than mountain summits: both were similar mid-season but the latter achieved larger size end-season in the absence of water stress. Transpiration rates were 6-fold greater for large vs. small plants, highlighting physiological significance of growth traits. These findings suggest strong differentiation of autotetraploid populations that mirrors local climate and edaphic features. Hybrid pedigrees are under construction between divergent populations to generate plants segregating for growth and phenology traits.

1 - Black Hills State University, School Of Natural Sciences, 1200 University Street, Unit 9095, Spearfish, SD, 57799, United States
2 - Black Hills State University, School Of Natural Sciences, 1200 University Street, Unit 9095, Spearfish, SD, 57799, USA

Keywords:
polyploidy
adaptation
phenology
ecophysiology
Asteraceae.

Presentation Type: Poster
Session: P, Biogeography Posters
Location: Arizona Ballroom/Starr Pass
Date: Monday, July 29th, 2019
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: PBG014
Abstract ID:1029
Candidate for Awards:None