Phenotypic selection and regulation of reproduction in different environments in wild barley

Abstract

Plasticity of the phenotypic architecture of wild barley, Hordeum spontaneum, was studied in response to water and nutrient stress. Direct and indirect selection on several vegetative and reproductive traits was estimated and path analysis used to reveal how regulating pathways via maternal investment differed between environments. Vegetative traits displayed differential regulating effect on fitness across experimental environments: (1) increase in size was selected for under optimal conditions and under water stress, but not under nutrient stress; (2) allocation to root biomass was selected for under optimal conditions, but it had no effect under nutrient stress and was strongly selected against when water was limiting; (3) delayed onset of reproduction was selected under nutrient limitation whereas earlier onset was selected under water stress. The regulating effect of reproductive traits on final reproductive output also differed across treatments, operating either at the ‘early’ stage of plant development through varying the number of initiated spikelets per spike (no stress and water stress treatment) or at the ‘late’ developmental stage adjusting the fertile spikelet weight (no stress and nutrient stress treatment). Reproductive output was regulated via seed abortion under no stress and water stress treatments. Although the underlying mechanism of the regulation through abortion has yet to be discovered, the specific mechanism of abortion under water stress appears to be different from that under optimal conditions. Our results demonstrate that not only is the character architecture in wild barley plastic and sensitive to changing availability of water and nutrients, but the regulating mechanism of maternal investment is also environmentally sensitive.

Introduction beyond a species range: a relationship between population origin, adaptive potential and plant performance

“…This means that plants from the species core were preadapted better to extremely arid Beer Sheva location. Negative selection on days to flowering and positive selection on individual spikelet weight under water stress was also observed in a methodologically similar study done on wild barley (Volis et al, 2004). Selection on seed size is complex, and optimal seed size appears to be a compromise between two selective forces acting in opposite directions (selection for seedling vigor and seed predation effect) (Gomez, 2004).…”

“…Selection for advance of flowering was found in several studies with experimentally induced drought stress (Stanton et al, 2000;Volis et al, 2004;Franks et al, 2007) and in a reciprocal transplant experiment with one desert and one Mediterranean site (Volis et al, . Although effects of flowering and maturation time on fitness in our study were found to be indirect and mediated by other traits, under drought, plants that flowered and set seeds earlier had higher fitness.…”

Distinguishing adaptive from nonadaptive genetic differentiation: comparison of QST and FST at two spatial scales

“…These traits were previously analyzed for phenotypic plasticity (Volis et al, 2002e) and involvement in the adaptative process (Volis et al, 2004), including involvement in region-specific adaptation (Volis et al, 2002c), using plants from one (pivot) population per region. In these experiments, DAW, SPL, SWT, AWL and TH were significant predictors of individual plant fitness.…”

Epistasis in natural populations of a predominantly selfing plant

“…Soil nitrogen was used as such a proxi to soil spatial heterogeneity in numerous studies (for example, Lechowicz and Bell, 1991;Miller et al, 1995;Schlesinger et al, 1996). Specifically in wild barley, very large differences in soil nutrient status between sites of locally adapted populations were detected (Verhoeven et al, 2004) and selective role of nutrient status in population divergence was shown experimentally (Verhoeven et al, 2004;Volis et al, 2004b).…”