A new family of standardized and symmetric indices for measuring the intensity and importance of plant neighbour effects

Díaz‐Sierra, Rubén; Verwijmeren, Mart; Rietkerk, Max; Dios, Víctor Resco de; Baudena, Mara

doi:10.1111/2041-210x.12706

Cited by 51 publications

(56 citation statements)

References 55 publications

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“…W −n was taken as the mean fitness of plants without neighbours within a growth chamber. RII is symmetric about zero enabling unbiased detection of competition and facilitation, and it is standardized so that the different competitive scenarios in this experiment can be directly compared (Diaz‐Sierra, Verwijmeren, Rietkerk, Dios, & Baudena, ; Weigelt & Jolliffe, ).…”

Section: Methodsmentioning

confidence: 99%

Phenological and fitness responses to climate warming depend upon genotype and competitive neighbourhood in Arabidopsis thaliana

2019

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Increasing temperatures during climate change are known to alter the phenology across diverse plant taxa, but the evolutionary outcomes of these shifts are poorly understood. Moreover, plant temperature‐sensing pathways are known to interact with competition‐sensing pathways, yet there remains little experimental evidence for how genotypes varying in temperature responsiveness react to warming in realistic competitive settings. We compared flowering time and fitness responses to warming and competition for two near‐isogenic lines (NILs) of Arabidopsis thaliana transgressively segregating temperature‐sensitive and temperature‐insensitive alleles for major‐effect flowering time genes. We grew focal plants of each genotype in intraspecific and interspecific competition in four treatments contrasting daily temperature profiles in summer and fall under contemporary and warmed conditions. We measured phenology and fitness of focal plants to quantify plastic responses to season, temperature and competition and the dependence of these responses on flowering time genotype. The temperature‐insensitive NIL was constitutively early flowering and less fit, except in a future‐summer climate in which its fitness was higher than the later flowering, temperature‐sensitive NIL in low competition. The late‐flowering NIL showed accelerated flowering in response to intragenotypic competition and to increased temperature in the summer but delayed flowering in the fall. However, its fitness fell with rising temperatures in both seasons, and in the fall its marginal fitness gain from decreasing competition was diminished in the future. Functional alleles at temperature‐responsive genes were necessary for plastic responses to season, warming and competition. However, the plastic genotype was not the most fit in every experimental condition, becoming less fit than the temperature‐canalized genotype in the warm summer treatment. Climate change is often predicted to have deleterious effects on plant populations, and our results show how increased temperatures can act through genotype‐dependent phenology to decrease fitness. Furthermore, plasticity is not necessarily adaptive in rapidly changing environments since a nonplastic genotype proved fitter than a plastic genotype in a warming climate treatment. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.13262/suppinfo is available for this article.

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Section: Methodsmentioning

confidence: 99%

Phenological and fitness responses to climate warming depend upon genotype and competitive neighbourhood in Arabidopsis thaliana

2019

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“…This measure is more suitable for quantifying competition and facilitation intensity than the more widely used relative interaction index (RII), which may underestimate facilitation (Díaz‐Sierra et al. ). The value NInt A was calculated for each subordinate species and pot using the equation

{normalNInt}_{normalA} = 2 Δ P / (P_{- N} + Δ P)

, where Δ P is the difference between aboveground biomass of the target subordinate species with neighbors ( P + N ) and without neighbors ( P − N ) of C. elata

(Δ P = P_{+ N} - P_{- N}) .

This index tends to a value of −1 for competitive exclusion and to +2 for obligate facilitation.…”

Section: Methodsmentioning

confidence: 99%

“…S2) are independent of the measure of species asynchrony used. To estimate the competition-facilitation balance (intensity of facilitation vs. competition) between the dominant and subordinate species across hydrological regimes, we used the additive intensity index (NInt A ; D ıaz- Sierra et al 2017). This measure is more suitable for quantifying competition and facilitation intensity than the more widely used relative interaction index (RII), which may underestimate facilitation (D ıaz- Sierra et al 2017).…”

Section: Statistical Analysesmentioning

confidence: 99%

“…To estimate the competition-facilitation balance (intensity of facilitation vs. competition) between the dominant and subordinate species across hydrological regimes, we used the additive intensity index (NInt A ; D ıaz- Sierra et al 2017). This measure is more suitable for quantifying competition and facilitation intensity than the more widely used relative interaction index (RII), which may underestimate facilitation (D ıaz- Sierra et al 2017). The value NInt A was calculated for each subordinate species and pot using the equation NInt A ¼ 2DP= P ÀN þ DP ð Þ , where DP is the difference between aboveground biomass of the target subordinate species with neighbors (P +N ) and without neighbors (P ÀN ) of C. elata ðDP ¼ P þN À P ÀN Þ: This index tends to a value of À1 for competitive exclusion and to +2 for obligate facilitation.…”

Section: Statistical Analysesmentioning

confidence: 99%

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Reduced competition enhances community temporal stability under conditions of increasing environmental stress

Douda

Doudová

Hulík

et al. 2018

Ecology

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The stress-gradient hypothesis predicts a switch from competition to facilitation, under increasing environmental stress. However, it is unclear how important is the change in competition-facilitation balance (i.e., the net outcome of plant-plant interactions) along the stress gradient in the regulation of community temporal stability (i.e., the inverse of temporal variability in total biomass). Increasing environmental stress may enhance community temporal stability by reduced competition or eventually by leading to facilitative interactions between the dominant and subordinate species. Here, we present the results of a 5-yr mesocosm experiment that demonstrates the effects of interspecific interactions on the temporal stability of a riparian community across different drought-stress scenarios. We constructed artificial communities of dominant species (Carex elata) and three subordinate species to simulate the independent effects of environmental stress and interspecific interactions. Using removal of the dominant species, we evaluated the interplay of various mechanisms regulating the temporal stability of the subordinate species (competition-facilitation balance, species asynchrony, and dominant species stability). By simultaneous testing of these stabilizing mechanisms, we show their importance differs depending on environmental variability and harshness. The predominant role is taken by species asynchrony in a seasonally dry environment, whereas in a permanently dry environment, the importance of reduced competition increases. Reduced competition was stabilizing, in particular through increased total community biomass, whereas species asynchrony increased total community biomass and decreased biomass variation. These results suggest experiments and simulations that exclude interspecific interactions may not offer realistic predictions of the effects of changing hydrological regimes on ecosystem functioning.

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“…Fisher’s exact test was used to compare the proportion of Crotalaria seedlings growing within or outside tussocks with the respective ratio of area taken up by tussocks and open soil. To quantify the interaction between Crotalaria and Stipagrostis , we calculated the Neighbor‐Effect Intensity Index (NInt A ) introduced by Díaz‐Sierra, Verwijmeren, Rietkerk, de Dios, and Baudena (2017) based on the average tussock area of Stipagrostis for each year. NInt A is defined as 2 *( dB )/( B 0 +| dB |), with B 0 = tussock area of Stipagrostis growing alone and dB = B 0 –tussock area of Stipagrostis growing with Crotalaria as competitor.…”

Section: Methodsmentioning

confidence: 99%

A dominance shift in arid savanna: An herbaceous legume outcompetes local C₄ grasses

Wagner

Richter

Joubert

et al. 2018

Ecology and Evolution

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The characteristic vegetation structure of arid savannas with a dominant layer of perennial grass is maintained by the putative competitive superiority of the C4 grasses. When this competitive balance is disturbed by weakening the grasses or favoring the recruitment of other species, trees, shrubs, single grass, or forb species can increase and initiate sudden dominance shifts. Such shifts involving woody species, often termed “shrub encroachment”, or the mass spreading of so‐called increaser species have been extensively researched, but studies on similar processes without obvious preceding disturbance are rare. In Namibia, the native herbaceous legume Crotalaria podocarpa has recently encroached parts of the escarpment region, seriously affecting the productivity of local fodder grasses. Here, we studied the interaction between seedlings of the legume and the dominant local fodder grass (Stipagrostis ciliata). We used a pot experiment to test seedling survival and to investigate the growth of Crotalaria in competition with Stipagrostis. Additional field observations were conducted to quantify the interactive effect. We found germination and growth of the legume seedlings to be facilitated by inactive (dead or dormant) grass tussocks and unhindered by active ones. Seedling survival was three times higher in inactive tussocks and Crotalaria grew taller. In the field, high densities of the legume had a clear negative effect on productivity of the grass. The C4 grass was unable to limit the recruitment and spread of the legume, and Crotalaria did outcompete the putative more competitive grass. Hence, the legume is able to spread and establish itself in large numbers and initiate a dominance shift in savannas, similar to shrub encroachment.

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A new family of standardized and symmetric indices for measuring the intensity and importance of plant neighbour effects

Cited by 51 publications

References 55 publications

Phenological and fitness responses to climate warming depend upon genotype and competitive neighbourhood in Arabidopsis thaliana

Phenological and fitness responses to climate warming depend upon genotype and competitive neighbourhood in Arabidopsis thaliana

Reduced competition enhances community temporal stability under conditions of increasing environmental stress

A dominance shift in arid savanna: An herbaceous legume outcompetes local C₄ grasses

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A new family of standardized and symmetric indices for measuring the intensity and importance of plant neighbour effects

Cited by 51 publications

References 55 publications

Phenological and fitness responses to climate warming depend upon genotype and competitive neighbourhood in Arabidopsis thaliana

Phenological and fitness responses to climate warming depend upon genotype and competitive neighbourhood in Arabidopsis thaliana

Reduced competition enhances community temporal stability under conditions of increasing environmental stress

A dominance shift in arid savanna: An herbaceous legume outcompetes local C4 grasses

Contact Info

Product

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A dominance shift in arid savanna: An herbaceous legume outcompetes local C₄ grasses