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Priority effects provide an advantage to early establishing species and are thought to significantly affect the course of succession. We conducted a 20-year long experiment sowing high- and low-diversity mixtures in an ex-arable field. We ask how long the effect of sowing persists and which sown species affect the course of succession. The experiment was established in the Czech Republic in five replicate blocks, each containing three random 10 × 10 m plots with three treatments: natural colonisation, sowing low- and high-diversity seed mixtures. The species cover was annually estimated in 12 permanent 1 m 2 quadrates within each plot. To identify the effects of sowing, we used an innovative method analysing the data separately for each year using Redundancy analysis (RDA) with identity of sown species as explanatory variables. In the first year, the effect of sowing was small; the peak of explained variability occurred between third and fifth year. The legacy of sowing was detectable in the natural colonisers for 18 years and in the sown species for the whole 20-year period. For some species, the difference between the plots where they were and were not sown remained significant for the whole 20-year period (e.g. Lathyrus pratensis) although the plots were adjacent and the area was mown with the same machine. Other ones (e.g. Trisetum flavescens) colonised all the plots evenly. The long-lasting effect of the initial sowing confirms contingency of successional pathway on the propagule pressure in the time of start of succession due to the priority effects.

Diaspores of myrmecochorous plants consist of a seed (or fruit) and an attached appendage (elaiosome) which attracts ants. The elaiosome is a food resource for ants, whereas the seed is an energy source for subsequent germination and plant establishment. Although myrmecochory occurs in many phylogenetically unrelated lineages, multiple phylogenetic lineages display similar variation in elaiosome and seed metabolite composition due to convergent evolution. We focused on four families (Amaryllidaceae, Boraginaceae, Papaveraceae and Poaceae) each represented by two species from different genera. Diaspores of three populations per species were sampled and concentrations of 60 metabolites from five groups (amino acids, fatty acids, organic acids, polyols and sugars) were determined for both elaiosomes and seeds. Variability in metabolite composition was decomposed by hierarchical ANOVA and variation partitioning using redundancy analysis (reflecting both species nested within families, crossed with seed vs. elaiosome). Differences in the metabolite composition of elaiosomes and seeds were consistent across multiple phylogenetic origins (with more pronounced differences at the level of individual metabolites than at the level of metabolite groups) and supported the idea of convergent evolution under strong selection pressure. Elaiosomes contained higher amounts of easily digestible metabolites (especially amino acids) than seeds. Fatty acids were not more concentrated in elaiosomes, which contradicts the literal translation of "elaiosome" (= oil body). The differentiation of metabolite composition closely reflected taxonomic relatedness, particularly at the family level. Differences among populations within species were small, so the metabolite composition can thus be considered as a trait with relatively low intraspecific variability.

The functional structures of communities respond to environmental changes by both species replacement (turnover) and within-species variation (intraspecific trait variability; ITV). Evidence is lacking on the relative importance of these two components, particularly in response to both short- and long-term environmental disturbance. We hypothesized that such short- and long-term perturbations would induce changes in community functional structure primarily via ITV and turnover, respectively. To test this we applied an experimental design across long-term mown and abandoned meadows, with each plot containing a further level of short-term management treatments: mowing, grazing and abandonment. Within each plot, species composition and trait values [height, shoot biomass, and specific leaf area (SLA)] were recorded on up to five individuals per species. Positive covariations between the contribution of species turnover and ITV occurred for height and shoot biomass in response to both short- and long-term management, indicating that species turnover and intraspecific adjustments selected for similar trait values. Positive covariations also occurred for SLA, but only in response to long-term management. The contributions of turnover and ITV changed depending on both the trait and management trajectory. As expected, communities responded to short-term disturbances mostly through changes in intraspecific trait variability, particularly for height and biomass. Interestingly, for SLA they responded to long-term disturbances by both species turnover and intraspecific adjustments. These findings highlight the importance of both ITV and species turnover in adjusting grassland functional trait response to environmental perturbation, and show that the response is trait specific and affected by disturbance regime history.

While an increasing number of indices for estimating the functional trait diversity of biological communities are being proposed, there is a growing demand by ecologists to clarify their actual implications and simplify index selection. Several key indices relate to mean trait dissimilarity between species within biological communities. Among them, the most widely used include (a) the mean species pairwise dissimilarity (MPD) and (b) the Rao quadratic entropy (and related indices). These indices are often regarded as redundant and promote the unsubstantiated yet widely held view that Rao is a form of MPD. Worryingly, existing R functions also do not always simplify the use and differentiation of these indices. In this paper, we show various distinctions between these two indices that warrant mathematical and biological consideration. We start by showing an existing form of MPD that considers species abundances and is different from Rao both mathematically and conceptually. We then show that the mathematical relationship between MPD and Rao can be presented simply as Rao = MPD × Simpson, where the Simpson diversity index is defined as 1 - dominance. We further show that this relationship is maintained for both species abundances and presence/absence. This evidence dismantles the paradigm that the Rao diversity is an abundance-weighted form of MPD and indicates that both indices can differ substantially at low species diversities. We discuss the different interpretations of trait diversity patterns in biological communities provided by Rao and MPD and then provide a simple R function, called "melodic," which avoids the unintended results that arise from existing mainstream functions.

In their recent study, Borowicz and Armstrong (Oecologia 169:783-792, 2012) investigated effects of nutrient availability and competition for light on a perennial root hemiparasite Pedicularis canadensis. Their study showed a reduction of community productivity as a result of hemiparasite infection independently of a clear positive effect of increased nutrients. In contrast, there was a minimal effect of increased competition for light on growth of the parasite. Here, we summarize the available data on the influence of nutrient availability (closely related to productivity) on temperate grassland root hemiparasites thus expanding the discussion presented by Borowicz and Armstrong (Oecologia 169:783-792, 2012). Most studies show that root hemiparasites are highly sensitive to elevated competition for light in productive environments, which is manifested as an increase in mortality coupled to a decrease in population density. Such responses reflect increased mortality of hemiparasite seedlings that are physiologically inefficient in terms of photosynthesis and nutrient acquisition owing to a limited root network and consequently, are highly sensitive to competition for light. However, the susceptibility of hemiparasites to competition for light tends to decrease for individuals that survive the critical seedling stage. Moreover, survivors benefit from elevated nutrient availability, resulting in increased growth and fecundity. Elevated productivity can thus have opposing effects on the survival and growth of hemiparasites depending on life stage. We conclude that the findings by Borowicz and Armstrong (Oecologia 169:783-792, 2012) are not in conflict with this general view that root hemiparasite population ecology is strongly influenced by competition for light in highly productive environments.

Spatial pattern of enchytraeids (Oligochaeta: Enchytraeidae) was studied in an experimental plot in an apple orchard near Bavorov, South Bohemia, Czechoslovakia. A total of 450 soil cores were taken in 1982, all individuals were determined (juveniles to genus, mature individuals to species) and counted. In total, 17 species of 4 genera were found. Both juveniles and mature individuals exhibited a distinctly aggregated spatial pattern. The distribution of the number of individuals in a sampling unit may be effectively fitted by the negative binomial distribution. The fit of Neyman type A distribution was considerably poorer. Comparing juveniles and mature individuals of the same genus using Lloyd's index of patchiness we found mature individuals to be slightly more aggregated than juveniles. Comparing the observed distribution of species number with that expected under the assumption of independence we may conclude that individuals appear in multispecies aggregation centres. These two conclusions support the hypothesis that aggregations are environmentally conditioned (abiotic factors and/or food availability) rather than caused by the type of reproduction.