Abstract Detail


Baskauf, Carol [1], Lindsey, Annie [2], Rogers, Will [6], Boyd, Jennifer [3], Anderson, Jill [4], Brzyski, Jessica [5], Cruse-Sanders, Jennifer [6].

Comparison of phenotypic plasticity and genetic diversity of a rare and a widespread species of Boechera (Brassicaceae), B. perstellata and B. laevigata.

Various factors have been hypothesized to be associated with a species’ geographic distribution, including widespread species having higher phenotypic plasticity and/or greater genetic diversity as compared to rare species.  Such factors are best examined by comparing congeneric species as phylogenetic and potentially ecological “controls”.  Four populations of the federally endangered Boechera perstellata (Brassicaceae) were compared with three populations of its widespread relative B. laevigata in three different growth chamber experiments examining the plants’ phenotypic responses to various environmental conditions during growth (low or moderate light, two different temperature regimes, and low or high soil moisture). The genetic variability of the study plants was also assayed at 17 shared microsatellite loci.  Survival was lower for both species under the high water treatment. Regardless of treatment, the two species differed for some traits such as leaf number and specific leaf area (SLA), with B. perstellata consistently being “leafier” as well as generally having higher SLA.  However, the two species had different responses to the low water treatment in terms of root length, with roots generally lengthening markedly for B. laevigata but not for B. perstellata, resulting in a significant species x water treatment interaction for root length, with B. laevigata showing greater plasticity for this trait.  In fact, most differences in plasticity between the two species involved root traits, as indicated by significant interactions (species x environmental treatment) for various root-related dependent variables, such as the “root mass fraction” (RMF, root mass/total biomass) and the root-to-shoot ratio for mass (RSR-mass), for which the interactions were significant under all experimental treatments, and root mass, for which the interactions were significant under both the temperature and water treatments.  There was also a significant species x water interaction for  “specific leaf area” (SLA, leaf area to leaf mass), and a species x temperature interaction for “specific root length” (SRL, root length/root biomass).  In all cases the widespread B. laevigata displayed greater plasticity than the rare B. perstellata. In most cases the plasticity trends were in the expected direction, with B. laevigata increasing allocation to roots under low soil water conditions.  Under higher temperature conditions, though, RSR-mass and RMF both decreased for B. laevigata, with some increase in shoot mass and decrease in root mass.  Means for genetic variability at microsatellite loci, averaged across populations, were much lower for surviving B. perstellata plants as compared with B. laevigata plants, with the widespread B. laevigata having roughly twice as many alleles per locus, twice as high levels of polymorphic loci, four times higher expected heterozygosity, and 100 times higher observed heterozygosity. However, there was great divergence in diversity levels among the three B. laevigata populations, with one population having extremely high levels of observed heterozygosity (perhaps due to apomixis) while individuals from another population showed no variability whatsoever.  Overall, though, the widespread B. laevigata has both greater phenotypic plasticity and higher levels of genetic diversity (at least at the species level) as compared with its rare congener.

1 - Biology, 681 Summer St., Clarksville, TN, 37040, United States
2 - Austin Peay State University, Biology, Clarksville, TN, 37044
3 - University Of Tennessee At Chattanooga, Dept 2653, 615 McCallie Avenue, Chattanooga, TN, 37403, United States
4 - University Of Georgia, Genetics, 120 E Green St, Athens, GA, 30602, United States
5 - Seton Hill University, 1 Seton Hill Dr, Greensburg, PA, 15601-1548, United States
6 - University of Georgia, State Botanical Garden of Georgia , 2450 S. Milledge Ave., Athens, GA, 30605

rare species
widespread species
Boechera perstellata
Boechera laevigata
Phenotypic plasticity
genetic variability.

Presentation Type: Oral Paper
Number: EPH3011
Abstract ID:833
Candidate for Awards:None

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