Evaluating grazing response strategies in winter annuals : A multi-trait approach

Plants minimize fitness losses through grazing by three fundamental strategies: tolerance, avoidance and escape. Annual species have been traditionally assumed to escape grazing through their short life cycle and seed dormancy; however, their grazing response strategies remain almost unexplored. How traits and their coordination affect species' grazing responses, and whether the generalized grazing model, which posits convergent filtering by grazing and drought, is applicable to this ecologically and economically important species group thus remain unclear. We used a trait-based approach to evaluate grazing response strategies of winter annuals from the Middle East. Across 23 species, we examined the coordination of 16 traits hypothesized to be relevant for grazing responses, and linked them to species' fecundity responses, as proxy for fitness responses, to simulated grazing in controlled conditions, to species' abundance responses to grazing in the field and to species' distribution along a large-scale rainfall gradient. Winter annuals exhibited both grazing escape and to a lesser extent tolerance indicated by (a) independent coordination of escape and tolerance traits, and (b) maintenance of higher fecundity in species with more pronounced escape or tolerance traits under simulated grazing. In the natural habitat, species with a more pronounced escape but not tolerance strategy maintained higher abundance under grazing in dry habitats, indicating convergent favouring of escape by both grazing and drought. However, this finding at the local scale was not mirrored by a strategy shift along a large-scale rainfall gradient. Synthesis. The convergent favouring of escape traits by grazing and drought in annuals is consistent with the generalized grazing model. This model, which has been developed for perennials based on the avoidance strategy, can thus be extended to annuals based on escape, a finding that should facilitate projecting consequences of global change in drylands dominated by annuals. © 2021 The Authors. Journal of Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Societ

Evaluating grazing response strategies in winter annuals : A multi-trait approach

Plants minimize fitness losses through grazing by three fundamental strategies: tolerance, avoidance and escape. Annual species have been traditionally assumed to escape grazing through their short life cycle and seed dormancy; however, their grazing response strategies remain almost unexplored. How traits and their coordination affect species' grazing responses, and whether the generalized grazing model, which posits convergent filtering by grazing and drought, is applicable to this ecologically and economically important species group thus remain unclear. We used a trait-based approach to evaluate grazing response strategies of winter annuals from the Middle East. Across 23 species, we examined the coordination of 16 traits hypothesized to be relevant for grazing responses, and linked them to species' fecundity responses, as proxy for fitness responses, to simulated grazing in controlled conditions, to species' abundance responses to grazing in the field and to species' distribution along a large-scale rainfall gradient. Winter annuals exhibited both grazing escape and to a lesser extent tolerance indicated by (a) independent coordination of escape and tolerance traits, and (b) maintenance of higher fecundity in species with more pronounced escape or tolerance traits under simulated grazing. In the natural habitat, species with a more pronounced escape but not tolerance strategy maintained higher abundance under grazing in dry habitats, indicating convergent favouring of escape by both grazing and drought. However, this finding at the local scale was not mirrored by a strategy shift along a large-scale rainfall gradient. Synthesis. The convergent favouring of escape traits by grazing and drought in annuals is consistent with the generalized grazing model. This model, which has been developed for perennials based on the avoidance strategy, can thus be extended to annuals based on escape, a finding that should facilitate projecting consequences of global change in drylands dominated by annuals. © 2021 The Authors. Journal of Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Societ

Do cultivated varieties of native plants have the ability to outperform their wild relatives?

Vast amounts of cultivars of native plants are annually introduced into the semi-natural range of their wild relatives for re-vegetation and restoration. As cultivars are often selected towards enhanced biomass production and might transfer these traits into wild relatives by hybridization, it is suggested that cultivars and the wild × cultivar hybrids are competitively superior to their wild relatives. The release of such varieties may therefore result in unintended changes in native vegetation. In this study we examined for two species frequently used in re-vegetation (Plantago lanceolata and Lotus corniculatus) whether cultivars and artificially generated intra-specific wild × cultivar hybrids may produce a higher vegetative and generative biomass than their wilds. For that purpose a competition experiment was conducted for two growing seasons in a common garden. Every plant type was growing (a.) alone, (b.) in pairwise combination with a similar plant type and (c.) in pairwise interaction with a different plant type. When competing with wilds cultivars of both species showed larger biomass production than their wilds in the first year only and hybrids showed larger biomass production than their wild relatives in both study years. As biomass production is an important factor determining fitness and competitive ability, we conclude that cultivars and hybrids are competitively superior their wild relatives. However, cultivars of both species experienced large fitness reductions (nearly complete mortality in L. corniculatus) due to local climatic conditions. We conclude that cultivars are good competitors only as long as they are not subjected to stressful environmental factors. As hybrids seemed to inherit both the ability to cope with the local climatic conditions from their wild parents as well as the enhanced competitive strength from their cultivars, we regard them as strong competitors and assume that they are able to outperform their wilds at least over the short-term

Estimated parameter means for the tested plant types of <i>Plantago lanceolata</i> in competition treatments.

<p>The figure shows biomass production of the different plant types (labels on the x-axis) grown pairwise with different competitors (see legend, competitor “none”  =  control). Vertical bars represent 95% credible intervals, based on the quantiles of the particular posterior distribution. For significance of the results, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071066#pone-0071066-t002" target="_blank">Table 2</a>. A) Vegetative biomass [g] in the first growing season, B) generative biomass [g] in the first growing season, C) vegetative biomass [g] in the second growing season, D) generative biomass [g] in the second growing season.</p

Estimated parameter means for the tested plant types of <i>Lotus corniculatus</i> in competition treatments.

<p>The figure shows biomass production of the different plant types (labels on the x-axis) grown pairwise with different competitors (see legend, competitor “none”  =  control). Vertical bars represent 95% credible intervals, based on the quantiles of the particular posterior distribution. For significance of the results, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071066#pone-0071066-t002" target="_blank">Table 2</a>. A) Vegetative biomass [g] in the first growing season, B) generative biomass [g] in the first growing season, C) vegetative biomass [g] in the second growing season, D) generative biomass [g] in the second growing season.</p

Estimated differences of parameters for tested hypotheses.^*

*<p>Example for reading. Hypothesis: cultivar [wild] > wild [cultivar] means: cultivars produce more biomass in competition with wilds than wilds in competition with cultivars.</p><p><i>ß</i>  =  estimated coefficient (mean of posterior distribution), <i>q_2.5%</i> and <i>q_97.5%</i> = 2.5% and 97.5% quantiles of the posterior distribution (95% credible interval), <i>p</i> = posterior probability that the estimated coefficient is smaller (for negative estimates) or larger (for positive estimates) than 0 is given. Differences in parameters with <i>p</i>≥0.95 and with 95% credible intervals that do not include or narrowly include zero are judged as significant. Significant differences are shown in bold.</p

Schriftenschau

In der Schriftenschau zum Kochia-Band 6 werden 8 für die Flora von Deutschland relevante Neuerscheinungen aus den Jahren 2006 bis 2011 besprochen