Abstract Detail



Ecology

Yakimowski, Sarah [1], Ferrish, Justin [2], Samis, Karen [2].

On the evolution of salt tolerance: divergence in fitness and physiology phenotypes between freshwater and marine populations of Cakile edentula.

Little is known about the extent to which the suite of traits that contribute to salt tolerance may vary among populations, and evolve in response to differences in environmental salinity. In this study we investigate salt tolerance traits at evolutionary ecology and physiological levels under ecologically-relevant saline environments for populations of the dune plant Cakile edentula. We compare populations from saline marine populations (C. edentula ssp. edentula) to non-saline freshwater populations (C. edentula var. lucsutris) under control vs. medium (190 mM NaCl; expected optimal for marine plants) and high (304 mM NaCl; 80% of seawater concentration) salinity conditions under common growth chamber conditions. From a physiological perspective, we found that individuals from marine populations experience less stress under salinity: individuals from marine dunes exhibit significantly lower RVF (ratio of variable fluorescence), indicative of lower osmotic stress, at moderate salinity compared to non-saline conditions. Marine plants also exhibit a beneficial plastic response increasing their leaf thickness at moderate salinity relative to non-salinity, whereas plants from freshwater environments decreased leaf thickness with increasing salinity. However, plants from both marine and freshwater environments exhibited >3x more seed under non-saline conditions than under moderate saline conditions. Therefore, from an evolutionary ecology perspective these marine populations may not be locally adapted to salinity, exhibiting higher seed fitness under non-saline conditions, consistent with the expansion of C. edentula from marine to freshwater habitat. Finally, we detected higher palisade cell height, potentially indicative of higher light absorption capacity, in freshwater than marine populations, suggesting that freshwater populations may have evolved ecotypic differences, released from the maintenance of costly physiological mechanisms in saline environments. Overall this study raises the possibility that despite possessing physiological mechanisms to commonly occupy saline dune habitat, the demographic reprieve in non-saline environments is substantial.  


1 - Queen's University, Biology, 116 Barrie St., Biosciences Complex, Kingston, Ontario, K7L 3N6, Canada
2 - University of Prince Edward Island, Biology

Keywords:
Salt stress
evolution
Biogeography
Ecophysiology.

Presentation Type: Oral Paper
Number: ECO5006
Abstract ID:784
Candidate for Awards:None


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