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3. Performance of three closely related Myosotis species in an experiment in which substrate quality and competition were manipulated

Creator:
Koutecká, Eva and Lepš, Jan
Type:
article and TEXT
Subject:
among-population variability, daughter rosettes, life span, pot experiment, rhizomes, stolons, and trade-off
Language:
English
Description:
Closely related species can be used for studying the ecological significance of their traits. The response in terms of survival, clonal growth and vegetative and generative characteristics of three related Myosotis species to competition and soil characteristics were studied in a three year pot experiment. Plants from four populations per species were cultivated in a factorial combination of substrate (nutrient-rich soil and mixtures with sand) and competition (with or without Holcus lanatus) treatments. Survival, clonal growth and the majority of the growth characteristics of all three Myosotis species were reduced by competition. The effect of substrate was less pronounced, and variable for various traits: the soil with sand mixture was more suitable for survival, clonal growth and seed germination whereas in the nutrient-rich soil plants were taller, but this effect was modified by competition. The differences among species corresponded well to expectation based on their known habitat preferences. Myosotis caespitosa, a species typical of short-term habitats such as emerged bottoms of ponds, exhibited the shortest life span and was also the most sensitive to competition: all plants of this species died in the competition treatment before the end of the second season. Nevertheless, the surviving plants (in the no-competition treatment) were able to form several daughter rosettes or stolons; some of them spread clonally till the third year. Myosotis palustris subsp. laxiflora, which inhabits the banks of rivers and brooks often disturbed by torrential floods, survived best and had the highest potential for clonal growth and spreading. Most plants of this species produced rhizomes and stolons and spread the furthest of all the three species. Myosotis nemorosa, which lives mostly in meadows, the most stable habitat of the studied congeners, but also a habitat with a strongly competitive matrix of species, was intermediate in terms of survival, and clonal growth, forming mainly short rhizomes. This species exhibited the highest among-population variability in all recorded characteristics, which might be due to its local adaptation to a wide spectrum of habitats. We argue that the details of prevailing disturbance regime, rather than some general disturbance intensity explain the clonal behaviour of the species compared.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/

4. Quantifying and interpreting functional diversity of natural communities

Creator:
Lepš, Jan, Bello, Francesco de, Lavorel, Sandra, and Berman, Sandra
Type:
article and TEXT
Subject:
biodiversity index, functional trait, grasslands, intraspecific and interspecific diversity, PCA, Rao index, resource use efficiency, sampling effect, SLA, and stable isotope
Language:
English
Description:
Quantifying the functional diversity in ecological communities is very promising for both studying the response of diversity to environmental gradients and the effects of diversity on ecosystem functioning (i.e. in “biodiversity experiments”). In our view, the Rao coefficient is a good candidate for an efficient functional diversity index. It is, in fact, a generalization of the Simpson’s index of diversity and it can be used with various measures of dissimilarity between species (both those based on a single trait and those based on several traits). However, when intending to quantify the functional diversity, we have to make various methodological decisions such as how many and which traits to use, how to weight them, how to combine traits that are measured at different scales and how to quantify the species’ relative abundances in a community. Here we discuss these issues with examples from real plant communities and argue that diversity within a single trait is often the most ecologically relevant information. When using indices based on many traits, we plead for careful a priori selection of ecologically relevant traits, although other options are also feasible. When combining many traits, often with different scales, methods considering the extent of species overlap in trait space can be applied for both the qualitative and quantitative traits. Another possibility proposed here is to decompose the variability of a trait in a community according to the relative effect of among- and within-species differentiation (with the latter not considered by current indices of functional diversity), in a way analogical to decomposition of Sum of squares in ANOVA. Further, we show why the functional diversity is more tightly related to species diversity (measured by Simpson index) when biomass is used as a measure of population abundance, in comparison with frequency. Finally, the general expectation is that functional diversity can be a better predictor of ecosystem functioning than the number of species or the number of functional groups. However, we demonstrate that some of the expectations might be overrated – in particular, the “sampling effect“ in biodiversity experiments is not avoided when functional diversity is used as a predictor.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/