The relationship between individual seed quality and maternal plant body size in crowded herbaceous vegetation

Aims In most natural plant populations, there is a strong right-skewed distribution of body sizes for reproductive plants—i.e. the vast majority are relatively small, suppressed weaklings that manage not just to survive effects of crowding/competition and other hazards but also to produce offspring. Recent research has shown that because of their relatively large numbers, these relatively small resident plants collectively contribute most of the seed offspring production available for the population in the next generation. However, the success of these offspring will depend in part on their quality, e.g. reflected by seed size and resource content. Accordingly, in the present study, we used material from natural populations of herbaceous species to test the null hypothesis that there is no significant relationship between body size variation in resident plants—resulting from between-site variation in the intensity of crowding/competition—and variation in the mass or N content of their individual seeds.Methods Using populations of 56 herbaceous species common in eastern Ontario, total above-ground dry plant mass, mean mass per seed and mean nitrogen (N) content per seed were recorded for a sample of the largest resident plants and also for the smallest reproductive plants growing in local neighbourhoods with the most severe crowding/competition from near neighbours.Important findings Mass per seed was numerically smaller from the smallest resident plants for most study species, but with few exceptions, this was not significantly different (P> 0.05) from mass per seed from the largest resident plants. The results therefore showed no general effect of maternal plant body size on individual seed mass, or N content. This suggests that the reproductive output of the smaller half of the resident plant size distribution within these populations is likely to contribute not just most of the seed production available for the next generation but also seed offspring that are just as likely—on a per individual basis—to achieve seedling/juvenile recruitment success as the seed offspring produced by the largest resident plants. This conflicts with the traditional 'size-advantage' hypothesis for predicting plant fitness under severe competition, and instead supports the recent 'reproductive-economy-advantage' hypothesis, where competitive fitness is promoted by capacity to produce offspring that—despite severe body size suppression imposed by neighbour effects—in turn have capacity to produce grand-offspring.     

Seed size variation: magnitude,distribution, and ecological correlates

Summary We examined seed-mass variation in 39 species (46 populations) of plants in eastern-central Illinois, USA. The coefficient of variation of seed mass commonly exceeded 20%. Significant variation in mean seed mass occurred among conspecific plants in most species sampled (by hierarchical ANOVA), averaging 38% of total variance. For most species, within-plant variation was the larger component of total variance, averaging 62% of total variance. Variation in seed mass among fruits within crops was significant in most species tested.We conclude that variation in seed mass among and within plants is widespread and common. There was little evidence of trade-offs between number of seeds and mean or variance of seed mass, and little correlational evidence of local competition for maternal resources. No consistent ecological (dispersal mode and growth form) correlates of variance of seed mass were evident.     

Effects of seed mass on seedling height and competition in European white oaks

The relationship between seed size and fitness in plants may depend on offspring density, especially in cases where seed size affects the outcome of competition. We investigated the relationship between seed mass, germination, intraspecific competition and seedling height in a glasshouse experiment on three European white oak species (Quercus robur, Q. petraea, Q. pubescens). Within offspring families, seed mass showed a moderate, but statistically significant effect on seedling height, i.e. seedlings from heavier seeds were slightly taller. In contrast, competition caused pronounced inequality in seedling height in pairs of competing seedlings, but in only 55.2% of all pairs the dominant competitor arose from the heavier seed. It is thus possible that a positive effect of seed mass on seedling growth can be mediated through the density of conspecific seedlings and that heterogeneity in offspring density will contribute to the maintenance of seed mass variation in oak populations.     

Understanding height-structured competition in forests: is there an R* for light?

Tree species differ from one another in, and display trade-offs among, a wide range of attributes, including canopy and understorey growth and mortality rates, fecundity, height and crown allometry, and crown transmissivity. But how does this variation affect the outcome of interspecific competition and hence community structure? We derive criteria for the outcome of competition among tree species competing for light, given their allometric and life-history parameters. These criteria are defined in terms of a new simple whole life-cycle measure of performance, which provides a simple way to organize and understand the many ways in which species differ. The general case, in which all parameters can differ between species, can produce coexistence, founder control or competitive exclusion: thus, competition for light need not be hierarchical as implied by R^* theory. The special case in which species differ only in crown transmissivity produces neutral dynamics. The special case in which species differ in all parameters except crown transmissivity gives hierarchical competition, where the equivalent of R^* is Zˆ*, the height at which trees enter the canopy in an equilibrium monoculture.     

Aggregated seed arrival alters plant diversity in grassland communities

Aims Species aggregation is commonly seen in plant communities and may increase diversity by causing intraspecific competition to exceed interspecific competition. One potential source of this spatial aggregation is seed dispersal but it is unclear to what extent aggregated seed distributions affect plant diversity in real communities. Using a field experiment, I tested whether uniform or aggregated seed arrival alters community structure and whether these effects vary with sowing density.Methods The experiment consisted of two spatial seeding treatments (uniform and aggregated) that were fully crossed with three seed density treatments. Sixty, 3 × 4-m plots were arrayed in a low-diversity grassland located in Kansas, USA. Each plot was divided into forty-eight, 0.5 × 0.5-m patches. For aggregated seeding treatments, each of the 15 species was sown into three randomly selected patches within the plot (3×15 = 45). To create a uniform species arrival but control for the seed addition method, all 15 species were sown into 45 individual patches (with three patches remaining unsown) within each plot. Seed mass for each species was held constant at the plot scale between uniform or aggregated treatments within a given level of the sowing density treatment. After two growing seasons, plant density was quantified for all sown species in 15 randomly selected patches from each plot.Important findings I found evidence for shifts in community structure in response to the different spatial seeding patterns. The evenness of added species was higher under aggregated than uniform sowing patterns. There was no detectable effect of aggregated seed sowing on species richness at 3.75 m 2 scale. However, when species richness was extrapolated to larger scales (11.25 m 2), aggregated sowing was predicted to have greater richness than uniform sowing. Effects of seed aggregation on community structure were apparent only at moderate to high sowing rates, yet the latter are within the range of measured seed dispersal in similar grasslands. Additionally, as sowing density increased, seed mass became an increasingly effective predictor of relative abundances for added species, but only under uniform sowing patterns supporting the idea that aggregated dispersal may buffer weaker (smaller seeded) species from competition during colonization. This is the first experiment to show that aggregated seed dispersal patterns can increase at least some components of plant diversity in undisturbed grasslands and suggests that previous seed dispersal experiments, which utilize uniform seed sowing, may underestimate the potential effect of dispersal on plant community structure.     

Using exclusion rate to unify niche and neutral perspectives on coexistence

The competitive exclusion principle is one of the most influential concepts in ecology. The classical formulation suggests a correlation between competitor species similarity and competition severity, leading to rapid competitive exclusion where species are very similar; yet neutral models show that identical species can persist in competition for long periods. Here, we resolve the conflict by examining two components of similarity – niche overlap and competitive similarity – and modeling the effects of each on exclusion rate (defined as the inverse of time to exclusion). Studying exclusion rate, rather than the traditional focus on binary outcomes (coexistence versus exclusion), allows us to examine classical niche and neutral perspectives using the same currency. High niche overlap speeds exclusion, but high similarity in competitive ability slows it. These predictions are confirmed by a well‐known model of two species competing for two resources. Under ecologically plausible scenarios of correlation between these two factors, the strongest exclusion rates may be among moderately similar species, while very similar and highly dissimilar competitors have very low exclusion rates. Adding even small amounts of demographic stochasticity to the model blurs the line between deterministic and probabilistic coexistence still further. Thus, focusing on exclusion rate, instead of on the binary outcome of coexistence versus exclusion, allows a variety of outcomes to result from competitive interactions. This approach may help explain species coexistence in diverse competitive communities and raises novel issues for future work.     

Effect of light on seed germination and seedling shape of succulent species from Mexico

Aims Light requirements for cactus seed germination have been considered to be associated with their adult plant height and seed mass, but this has not been thoroughly studied for other succulent species. In order to understand seed photosensitivity from desert species belonging to Asparagaceae (subfamily Agavoideae) and Cactaceae, we performed a germination experiment with and without light for 12 species and 2 varieties from 1 species from the Southern Chihuahuan Desert. We also determined if adult growth is totally determined by seedling 'growth form' in cacti.Methods We performed a germination experiment using light and darkness for 13 species from Southern Chihuahuan Desert: 10 rosette species (Asparagaceae), as well as 1 globose, 1 columnar and 2 varieties from 1 depressed-globose species (Cactaceae). The response variables were seed germination percentage and relative light germination (RLG). In addition, in order to determine if adult-globose cacti could have cylindrical seedlings, we calculated the shape index (height/width ratio) for Coryphanta clavata and Mammillaria compressa .Important findings All species were considered neutral photoblastic. Eleven species had similar seed germination in both light and dark conditions, and three taxa (M. compressa and the two varieties of Ferocactus latispinus) showed higher germination with light than without it. Agave salmiana, M. compressa and the two varieties of F. latispinus had higher RLG than the other species. Seed mass was an important factor because with higher seed mass there was lower dependence to light. These findings support the hypothesis that small seed mass and light requirements have coevolved as an adaptation to ensure germination. One adult-globose cactus species, M. compressa, and one adult-columnar species, C. clavata, had small seeds and neutral fotoblasticism. Seedlings from these two species exposed to light were cylindrical and those under darkness conditions were columnar. Perhaps seeds from this species are able to germinate in the dark because they produce columnar seedlings with the ability to emerge from greater soil depths where sunlight cannot penetrate.     

Functional trade‐offs and the phylogenetic dispersion of seed traits in a biodiversity hotspot of the Mountains of Southwest China

The diversity of traits associated with plant regeneration is often shaped by functional trade‐offs where plants typically do not excel at every function because resources allocated to one function cannot be allocated to another. By analyzing correlations among seed traits, empirical studies have shown that there is a trade‐off between seedling development and the occupation of new habitats, although only a small range of taxa have been tested; whether such trade‐off exists in a biodiverse and complex landscape remains unclear. Here, we amassed seed trait data of 1,119 species from a biodiversity hotspot of the Mountains of Southwest China and analyzed the relationship between seed mass and the number of seeds and between seed mass and time to germination. Our results showed that seed mass was negatively correlated with seed number but positively correlated with time to germination. The same trend was found regardless of variation in life‐form and phylogenetic conservatism. Furthermore, the relation between seed mass and other seed traits was randomly dispersed across the phylogeny at both the order and family levels. Collectively, results suggest that there is a functional trade‐off between seedling development and new habitat occupation for seed plants in this region. Larger seeds tend to produce fewer seedlings but with greater fitness compared to those produced by smaller seeds, whereas smaller seeds tend to have a larger number of seeds that germinate faster compared to large‐seeded species. Apart from genetic constraints, species that produce large seeds will succeed in sites where resource availability is low, whereas species with high colonization ability (those that produce a high number of seeds per fruit) will succeed in new niches. This study provides a mechanistic explanation for the relatively high levels of plant diversity currently found in a heterogeneous region of the Mountains of Southwest China.     

Niches, rather than neutrality, structure a grassland pioneer guild

Pioneer species are fast-growing, short-lived gap exploiters. They are prime candidates for neutral dynamics because they contain ecologically similar species whose low adult density is likely to cause widespread recruitment limitation, which slows competitive dynamics. However, many pioneer guilds appear to be differentiated according to seed size. In this paper, we compare predictions from a neutral model of community structure with three niche-based models in which trade-offs involving seed size form the basis of niche differentiation. We test these predictions using sowing experiments with a guild of seven pioneer species from chalk grassland. We find strong evidence for niche structure based on seed size: specifically large-seeded species produce fewer seeds but have a greater chance of establishing on a per-seed basis. Their advantage in establishment arises because there are more microsites suitable for their germination and early establishment and not directly through competition with other seedlings. In fact, seedling densities of all species were equally suppressed by the addition of competitors' seeds. By the adult stage, despite using very high sowing densities, there were no detectable effects of interspecific competition on any species. The lack of interspecific effects indicates that niche differentiation, rather than neutrality, prevails.     

Co-evolution of seed size and seed predation

Using the evolutionarily stable strategy (ESS) approach in a model for the co-evolution of seed size and seed predation, I show that seed size variation within individual plants is favoured if there is a trade-off in the predator's attack rate for different seed sizes. A single seed size is not evolutionarily stable because a predator that is optimally adapted to one particular seed size cannot prevent invasion by plants with a different seed size. The model generates the following predictions. The ESS consists of a continuous range of seed sizes. Small seeds tend to be attacked more frequently than big seeds. Plants with many resources and plants with low (frequency-independent) juvenile mortality have more variable seeds than plants with few resources and a high juvenile mortality. Seed size variation is higher in fluctuating populations regulated by seed predation alone than in stable populations (partially) regulated by seedling competition. Predator searching behaviour does not directly affect the ESS seed size range, but may have an indirect effect by affecting population stability or the significance of seedling competition as a population regulating mechanism. Moreover, seed size distributions are found to be more skewed in favour of small seeds if predation is spatially non-uniform than if predation is more even. Application of the model to systems of several co-evolving plant and predator species is discussed.     

Geographical gradients in seed mass in relation to climate

Aim To determine whether latitudinal and longitudinal gradients in seed mass are related to variation in climatic features including temperature, solar radiation and rainfall. Location Australia. Methods Seed mass was estimated from over 1600 provenances covering the latitudinal and longitudinal extents of 34 perennial Glycine taxa in Australia. Climatic data were obtained from ANUCLIM 5.1 for collection locations based on long‐term meteorological records across Australia. These climatic data were subject to principal components analysis to extract three components as climatic indices. Generalized linear models were used in three separate sets of analyses to evaluate whether seed mass–latitude and seed mass–longitude relationships persisted after taking climatic variation into account. First, relationships were examined across species in analyses that did not explicitly consider phylogenetic relationships. Secondly, phylogenetic regressions were performed to examine patterns of correlated evolutionary change throughout the Glycine phylogeny. Within‐species analysis was also performed to examine consistency across different taxonomic levels. Results Geographical variation in seed mass among species was related primarily to temperature and solar radiation, while rainfall was much less influential upon seed mass. Partialing out the influence of temperature and solar radiation in models resulted in the disappearance of significant seed mass–latitude and seed mass–longitude relationships. Patterns within species were generally consistent with patterns among species. However, in several species, factors additional to these climatic variables may contribute to the origin and maintenance of geographical gradients in seed mass, as significant seed mass–latitude and seed mass–longitude relationships remained after controlling for the influence of climatic variables. Main conclusions Our empirical results support the hypotheses that (1) seed mass is larger at low latitudes and in the interior of the Australian continent due to increased metabolic costs at high temperatures, and that (2) higher levels of solar radiation result in an increase in the availability of photosynthate, which in turn leads to an increase in biomass for the production of large seeds. In effect, our findings show that greater energy is available precisely where needed, that is, where high temperatures require large seed mass on the basis of metabolic requirements.     

Low-dimensional trade-offs fail to explain richness and structure in species-rich plant communities

Mathematical models and ecological theory suggest that low-dimensional life history trade-offs (i.e. negative correlation between two life history traits such as competition vs. colonisation) may potentially explain the maintenance of species diversity and community structure. In the absence of trade-offs, we would expect communities to be dominated by ‘super-types’ characterised by mainly positive trait expressions. However, it has proven difficult to find strong empirical evidence for such trade-offs in species-rich communities. We developed a spatially explicit, rule-based and individual-based stochastic model to explore the importance of low-dimensional trade-offs. This model simulates the community dynamics of 288 virtual plant functional types (PFTs), each of which is described by seven life history traits. We consider trait combinations that fit into the trade-off concept, as well as super-types with little or no energy constraints or resource limitations, and weak PFTs, which do not exploit resources efficiently. The model is parameterised using data from a fire-prone, species-rich Mediterranean-type shrubland in southwestern Australia. We performed an exclusion experiment, where we sequentially removed the strongest PFT in the simulation and studied the remaining communities. We analysed the impact of traits on performance of PFTs in the exclusion experiment with standard and boosted regression trees. Regression tree analysis of the simulation results showed that the trade-off concept is necessary for PFT viability in the case of weak trait expression combinations such as low seed production or small seeds. However, species richness and diversity can be high despite the presence of super-types. Furthermore, the exclusion of super-types does not necessarily lead to a large increase in PFT richness and diversity. We conclude that low-dimensional trade-offs do not provide explanations for multi-species co-existence contrary to the prediction of many conceptual models.     

Competition in variable environments: experiments with planktonic rotifers

1. In a constant environment, competition often tends to reduce species diversity. However, several theories predict that temporal variation in the environment can slow competitive exclusion and allow competing species to coexist. This study reports on laboratory competition experiments in which two pairs of planktonic rotifer species competed for a phytoplankton resource under different conditions of temporal variability in resource supply.
2. For both species pairs, Keratella cochlearis dominated under all conditions of temporal variability, and the other species ( Brachionus calyciflorus or Synchaeta sp.) almost always went extinct. Increasing temporal variation in resource supply slowed competitive exclusion but did not change competitive outcome or allow coexistence.
3. Rotifers show a gleaner–opportunist trade-off, because gleaner species have low threshold resource levels ( R *) and low maximum population growth rates, while opportunist species have the opposite characteristics. In the competition experiments, the gleaner always won and the opportunists always lost. Thus, a gleaner–opportunist trade-off was not sufficient to facilitate coexistence under conditions of resource variability. Instead, the winning species had both the lowest R * and the greatest ability to store resources and ration their use during times of extreme resource scarcity.     

Host‐parasitoid dynamics in periodic boreal moths

We analyse the population and spatial structures of coastal annual-plant communities, across ten dunes and three years, to explore the role of seed mass in structuring these communities. One suggestion is that annual-plant communities are structured by competition-colonization trade-offs driven by difference among species in seed-allocation strategies, while another perspective is that seed mass influences the ways in which species respond to environmental variation. In support of the competition-colonization trade-off, the two largest-seeded species found on the dunes ( Erodium cicutarium and Geranium molle ) were negatively associated with the other guild members at the 10-mm scale in 1995, suggesting they locally excluded smaller-seeded species in that year (when population densities were high). In support of the environmental response hypothesis, populations of annual plants declined between 1995 and 1996 on eight of the ten dunes, underscoring the importance of year-to-year environmental fluctuations in determining population sizes. The species that became relatively uncommon also became more aggregated in space, and this effect was most pronounced among the small-seeded species. Thus, small-seeded species may be forced to retreat into refuges when conditions are unfavourable, where reduced frequencies of interspecific contacts may increase their chances of persistence. We also show that small-seeded species sometimes reach much higher population densities than larger-seeded species, consistent with earlier findings, but reason that this abundance/seed mass relationship could have resulted from either a competition-colonization trade-off or from different responses of small- and large-seeded species to environmental variation. We conclude that dune-annual species with contrasting seed masses respond differently to environmental variation, while the competition-colonization trade-off plays a lesser role in community dynamics than previously considered.     

Latitude, seed predation and seed mass

Aim We set out to test the hypothesis that rates of pre‐ and post‐dispersal seed predation would be higher towards the tropics, across a broad range of species from around the world. We also aimed to quantify the slope and predictive power of the relationship between seed mass and latitude both within and across species. Methods Seed mass, pre‐dispersal seed predation and post‐dispersal seed removal data were compiled from the literature. Wherever possible, these data were combined with information regarding the latitude at which the data were collected. Analyses were performed using both cross‐species and phylogenetic regressions. Results Contrary to expectations, we found no significant relationship between seed predation and latitude (log₁₀ proportion of seeds surviving predispersal seed predation vs. latitude, P = 0.63; R² = 0.02; n = 122 species: log₁₀ proportion of seeds remaining after postdispersal seed removal vs. latitude, P = 0.54; R² = 0.02; n = 205 species). These relationships remained non‐significant after variation because of seed mass was accounted for. We also found a very substantial (R² = 0.21) relationship between seed mass and latitude across 2706 species, with seed mass being significantly higher towards the tropics. Within‐species seed mass decline with latitude was significant, but only about two‐sevenths, as rapid as the cross‐species decline with latitude. Results of phylogenetic analyses were very similar to cross‐species analyses. We also demonstrated a positive relationship between seed mass and development time across ten species from dry sclerophyll woodland in Sydney (P < 0.001; R² = 0.77; Standardized Major Axis slope = 0.14). These data lend support to the hypothesis that growing period might affect the maximum attainable seed mass in a given environment. Main conclusions There was no evidence that seed predation is higher towards the tropics. The strong relationship between seed mass and latitude shown here had been observed in previous studies, but had not previously been quantified at a global scale. There was a tenfold reduction in mean seed mass for every c. 23° moved towards the poles, despite a wide range of seed mass within each latitude.     

Ecological niche and phylogeny explain distribution of seed mass in the central European flora

Seed size is a crucial life‐history trait determining the amount of reserves that are available to establishing seedlings. The most frequently observed patterns in seed size distribution are a higher frequency of large‐seeded species in shaded habitats and a positive correlation of seed size with plant size. We analysed to what extent realised niche dimensions, as expressed by Ellenberg indicator values and plant functional traits such as plant height and life form, explained seed mass variation in the central European flora. By including information on phylogenetic relatedness of the species, not only contemporary ecology but also the evolutionary history of plant species could be taken into account. Seed mass evolution was slow and was best explained by selection‐inertia models with multiple adaptive peaks as a function of either habitat or life form. The highest seed mass optima were observed in the deciduous forest and saltwater and seashore habitats, and in phanerophytes in case of models with optima as a function of life form. The analyses showed that Ellenberg values were more important than habitat and life form in explaining seed mass distribution in the central European flora. The often observed relation between shade and large seeds was also evident in our study, but we found an equally important relation between large seeds and drought and a positive relation between seed mass and salinity. Our results indicate that not only plant size and competition for light but a complex set of factors influence the ecology of seed size, and that a more precise delineation of species’ niches improves the understanding of seed size evolution.     

Do large‐seeded herbs have a small range size? The seed mass–distribution range trade‐off hypothesis

We aimed to introduce and test the “seed mass–distribution range trade‐off” hypothesis, that is, that range size is negatively related to seed mass due to the generally better dispersal ability of smaller seeds. Studying the effects of environmental factors on the seed mass and range size of species, we also aimed to identify habitats where species may be at risk and need extra conservation effort to avoid local extinctions. We collected data for seed mass, global range size, and indicators for environmental factors of the habitat for 1,600 species of the Pannonian Ecoregion (Central Europe) from the literature. We tested the relationship between species’ seed mass, range size, and indicator values for soil moisture, light intensity, and nutrient supply. We found that seed mass is negatively correlated with range size; thus, a seed mass–distribution range trade‐off was validated based on the studied large species pool. We found increasing seed mass with decreasing light intensity and increasing nutrient availability, but decreasing seed mass with increasing soil moisture. Range size increased with increasing soil moisture and nutrient supply, but decreased with increasing light intensity. Our results supported the hypothesis that there is a trade‐off between seed mass and distribution range. We found that species of habitats characterized by low soil moisture and nutrient values but high light intensity values have small range size. This emphasizes that species of dry, infertile habitats, such as dry grasslands, could be more vulnerable to habitat fragmentation or degradation than species of wet and fertile habitats. The remarkably high number of species and the use of global distribution range in our study support our understanding of global biogeographic processes and patterns that are essential in defining conservation priorities.     

Life History Evolution in Amphicarpic Plants

Abstract Plants with dimorphic flowers or seeds provide excellent material for the study of life history evolution because the dimorphism often involves measurable differences in morphology, size, number, or genetic relatedness. For amphicarpic plants, the proportion of aerial: subterranean morphs produced is highly variable (from 0 to > 100) and related to both environmental and genetic factors. Plants from aerial seeds produce lower ratios of aerial: subterranean morphs than those from subterranean seeds. Despite substantial variation, subterranean seeds are generally heavier than aerial seeds (but fewer) and produce vigorous seedlings with high survivorship and high fitness. Adaptive advantages of subterranean seeds include retention of offspring in favorable parental microhabitats, protection of seeds from herbivory, predation, or fire, and avoidance of desiccating conditions on the soil surface; potential disadvantages include lack of gene exchange, high energy costs, limited dispersal, and sibling competition. For the few species studied, aerial reproduction is more plastic than subterranean reproduction and more likely to be affected by environmental conditions. Quantitative genetic analyses of a population of the annual grass Amphicarpum purshii have revealed lower heritabilites for subterranean relative to aerial reproductive traits. Subterranean seed number and mass show genetic correlations with shoot mass while aerial seed number and mass do not; seed set percentages of both seed types as well as percentage allocation to both reproductive morphs show negative genetic correlations with shoot mass. In this Amphicarpum population, directional selection on shoot mass may indirectly select for increased subterranean (but not aerial) seed output.     

Root:shoot ratio in developing seedlings: How seedlings change their allocation in response to seed mass and ambient nutrient supply

Root:shoot (R:S) biomass partitioning is one of the keys to the plants' ability to compensate for limiting resources in the environment and thus to survive and succeed in competition. In adult plants, it can vary in response to many factors, such as nutrient availability in the soil or reserves in the roots from the previous season. The question remains whether, at the interspecific level, reserves in seeds can affect seedlings' R:S ratio in a similar way. Proper allocation to resource‐acquiring organs is enormously important for seedlings and is likely to determine their survival and further success. Therefore, we investigated the effect of seed mass on seedling R:S biomass partitioning and its interaction with nutrient supply in the substrate. We measured seedling biomass partitioning under two different nutrient treatments after 2, 4, 6, and 12 weeks for seventeen species differing in seed mass and covering. We used phylogenetically informed analysis to determine the independent influence of seed mass on seedling biomass partitioning. We found consistently lower R:S ratios in seedlings with higher seed mass. Expectedly, R:S was also lower with higher substrate nutrient supply, but substrate nutrient supply had a bigger effect on R:S ratio for species with higher seed mass. These findings point to the importance of seed reserves for the usage of soil resources. Generally, R:S ratio decreased over time and, similarly to the effect of substrate nutrients, R:S ratio decreased faster for large‐seeded species. We show that the seed mass determines the allocation patterns into new resource‐acquiring organs during seedling development. Large‐seeded species are more flexible in soil nutrient use. It is likely that faster development of shoots provides large‐seeded species with the key advantage in asymmetric above‐ground competition, and that this could constitute one of the selective factors for optimum seed mass.