Structure Of Plant Populations Research Articles

Effects of zoochory on the spatial genetic structure of plant populations.

Spatial genetic structure (SGS) of plants results from the nonrandom distribution of related individuals. SGS provides information on gene flow and spatial patterns of genetic diversity within populations. Seed dispersal creates the spatial template for plant distribution. Thus, in zoochorous plants, dispersal mode and disperser behaviour might have a strong impact on SGS. However, many studies only report the taxonomic group of seed dispersers, without further details. The recent increase in studies on SGS provides the opportunity to review findings and test for the influence of dispersal mode, taxonomic affiliation of dispersers and their behaviour. We compared the proportions of studies with SGS among groups and tested for differences in strength of SGS using Sp statistics. The presence of SGS differed among taxonomic groups, with reduced presence in plants dispersed by birds. Strength of SGS was instead significantly influenced by the behaviour of seed dispersal vectors, with higher SGS in plant species dispersed by animals with behavioural traits that result in short seed dispersal distances. We observed high variance in the strength of SGS in plants dispersed by animals that actively or passively accumulate seeds. Additionally, we found SGS was also affected by pollination and marker type used. Our study highlights the importance of vector behaviour on SGS even in the presence of variance created by other factors. Thus, more detailed information on the behaviour of seed dispersers would contribute to better understand which factors shape the spatial scale of gene flow in animal-dispersed plant species.

Pleistocene megafaunal extinctions and the functional loss of long‐distance seed‐dispersal services

Pleistocene extinctions affected mainly large‐bodied animals, determining the loss or changes in numerous ecological functions. Evidence points to a central role of many extinct megafauna herbivores as seed dispersers. An important step in understanding the legacy of extinct mutualistic interactions is to evaluate the roles and effectiveness of megafauna herbivores in seed dispersal. Here we use morphological and ecophysiological allometries to estimate both quantitative and qualitative aspects of seed‐dispersal services likely provided by extinct megafauna. We developed a mechanistic model that encompasses four stages of seed dispersal – seed ingestion, gut retention, animal movement, and seed deposition. We estimate seed‐dispersal kernels through simulations to infer the role of Pleistocene megafauna in promoting long‐distance dispersal and examine how seed dispersal was affected by extinctions. Simulations suggest extinct large‐bodied frugivores would frequently disperse large seeds over a thousand meters, whereas smaller‐bodied frugivores are more likely to deposit the seeds over a few hundred meters. Moreover, events of long‐distance seed dispersal by the extinct megafauna would be up to ten times longer than long‐distance dispersal by smaller‐sized extant mammals. By estimating the combined distribution of seed dispersal distances considering all large‐bodied mammalian frugivores in specific South American Pleistocene assemblages we found that long‐distance dispersal contracted by at least two thirds after the megafauna died out. The disruption of long‐distance dispersal is expected to have consequences for recruitment, spatial and genetic structure of plant populations, population persistence and community composition. Promoting long‐distance seed dispersal was one among other salient features of extinct Pleistocene megafauna that reveal their influence on natural ecosystems. Modeling the consequences of megafaunal extinctions can offer quantitative predictions on the consequences of ongoing defaunation to plant populations and ecological communities.

Accounting for biotic spatial variability in fields: Case of resistance screening against sunflower Verticillium wilt.

In breeding for disease resistance, the magnitude of the genetic response is difficult to appreciate because of environmental stresses that interact with the plant genotype. We discuss herein the fundamental problems in breeding for disease resistance with the aim being to better understand the interactions between plant, pathogen, and spatial patterns. The goal of this study is to fine tune breeding decisions by incorporating spatial patterns of such biotic factors into the definition of disease-occurrence probability. We use a preexisting statistics method based on geostatistics for a descriptive analysis of biotic factors for trial quality control. The plant-population structure used for spatial-pattern analysis consists of two F1-hybrid cultivars, defined as symptomatic and asymptomatic controls with respect to the studied pathogen. The controls are inserted at specific locations to establish a grid arrangement over the field that include the F1-hybrid cultivars under evaluation. We characterize the spatial structure of the pathogen population and of the general plant environment—with undetermined but present abiotic constraints—not by using direct notation such as flower time or rainfall but by using plant behavior (i.e., leaf symptom severity, indirect notation). The analysis indicates areas with higher or lower risk of disease and reveals a correlation between the symptomatic control and the effective level of disease for sunflowers. This result suggests that the pathogen and/or abiotic components are major factors in determining the probability that a plant develops the disease, which could lead to a misinterpretation of plant resistance.

Genetic diversity and structure of the treeManilkara zapotain a naturally fragmented tropical forest

Abstract:Forest fragmentation, habitat loss and isolation may have a strong effect on biodiversity in tropical forests. This can include modification of the genetic diversity and structure of plant populations. In this study, we assessed the genetic diversity and structure of the treeManilkara zapotain 15 naturally formed fragments of semi-evergreen tropical forest, as well as in an adjacent continuous forest for comparison. Forest fragments were scattered within a matrix of wetlands and were highly variable in terms of size and degree of isolation. The naturally fragmented populations ofM.zapotahad slightly less allelic diversity (Ar: 3.4) than those of the continuous forest (Ar: 3.6), when corrected for sample size. However, populations in the fragments and continuous forest had very similar heterozygosity levels (HE: 0.59 in both cases). Low levels of genetic differentiation were observed among populations (FST: 0.026) and genetic structure was not consistent with isolation by distance, indicating high levels of gene flow. Genetic diversity was not explained by fragment size or degree of isolation. The relatively high genetic diversity and low inter-population genetic differentiation observed inM. zapotamay be the result of long-distance pollen and seed dispersal, as well as the high proximity among patches.

Changes of the genetic structure in chronically irradiated scots pine populations

Summary: Background. The vast forest areas were affected by radioactive fallout of the Chernobyl accident. Data about the long-term effects of chronic radiation exposure are insufficient, as well as knowledge about its influence on the genetic structure of populations. Study of isozyme polymorphism allows us to identify how chronic low-dose radiation exposure affects the genetic structure of plant populations and to develop new methods for assessing the biological effects of anthropogenic impact on terrestrial ecosystems.
 Materials and methods. The study was conducted in six sites in the Bryansk region (4 radioactively contaminated and 2 reference ones). The method of vertical electrophoresis in PAAG was used for estimation of polymorphism of three enzymes involved in metabolic pathways. Activity of enzymes in seeds of Scots pine was assessed by spectrophotometry.
 Results. The frequency of mutations in isozymes loci increased along the level of radiation exposure (7-130 mGy/year), as well as some characteristics of the genetic structure of populations. Biochemical activity of studied enzymes does not depend on the level of dose absorbed in the generative organs of pine.
 Conclusions. It was found that the frequency of mutational events in loci of catabolic/anabolic enzymes and in the loci of previously studied antioxidant enzymes increases along the level of radiation exposure. The degree of the biological effect of chronic exposure was different in groups of catabolic/anabolic enzymes and antioxidant enzymes. Radiation exposure contributes to changes in the genetic structure of Scots pine populations.

Plant-disperser mutualisms in a semi-arid habitat invaded by Lantana camara L.

Dispersal is an important ecological process that affects plant population structure and community composition. Invasive plants with fleshy fruits rapidly form associations with native and invasive dispersers, and may affect existing native plant-disperser associations. We asked whether frugivore visitation rate and fruit removal was associated with plant characteristics in a community of fleshy-fruited plants and whether an invasive plant receives more visitation and greater fruit removal than native plants in a semi-arid habitat of Andhra Pradesh, India. Tree-watches were undertaken at individuals of nine native and one invasive shrub species to assess the identity, number and fruit removal by avian frugivores. Network analyses and generalised linear mixed-effects models were used to understand species and community-level patterns. All plants received most number of visits from abundant, generalist avian frugivores. Number of frugivore visits and time spent by frugivores at individual plants was positively associated with fruit crop size, while fruit removal was positively associated with number of frugivore visits and their mean foraging time at individual plants. The invasive shrub, Lantana camara L. (Lantana), had lower average frugivore visit rate than the community of fleshy-fruited plants and received similar average frugivore visits but greater average per-hour fruit removal than two other concurrently fruiting native species. Based on the results of our study, we infer that there is little evidence of competition between native plants and Lantana for the dispersal services of native frugivores and that more data are required to assess the nature of these interactions over the long term. We speculate that plant associations with generalist frugivores may increase the functional redundancy of this frugivory network, buffering it against loss of participating species.

Keeping it in the family: strong fine-scale genetic structure and inbreeding in Lodoicea maldivica, the largest-seeded plant in the world

The fine-scale spatial genetic structure (FSGS) of plant populations is strongly influenced by patterns of seed dispersal. An extreme case of limited dispersal is found in the charismatic yet endangered palm Lodoicea maldivica, which produces large fruits (up to 20 kg) dispersed only by gravity. To investigate patterns of seed dispersal and FSGS in natural populations we sampled 1252 individual adults and regenerating offspring across the species’ natural range in the Seychelles archipelago, and characterised their genotypes at 12 microsatellite loci. The average dispersal distance was 8.7 ± 0.7 m. Topography had a significant effect on seed dispersal, with plants on steep slopes exhibiting the longest distances. FSGS was intense, especially in younger cohorts. Contrary to what might be expected in a dioecious species, we found high levels of inbreeding, with most neighbouring pairs of male and female trees (≤10 m) being closely related. Nonetheless, levels of genetic diversity were relatively high and similar in the various sampling areas, although these differed in disturbance and habitat fragmentation. We discuss potential trade-offs associated with maternal resource provisioning of progeny, seed dispersal and inbreeding, and consider the implications of our findings for managing this globally significant flagship species.

Genetic population structure of sugarcane aphid, Melanaphis sacchari, in sorghum, sugarcane, and Johnsongrass in the continental USA

AbstractIn 2013, an outbreak of Melanaphis sacchari Zehntner (Hemiptera: Aphididae) was reported in sorghum in Texas, USA. Although this aphid has been reported in the continental USA for nearly a century, its occurrence was limited to Florida and Louisiana sugarcane. After 2013 and within just 3 years M. sacchari was reported in almost all sorghum growing regions from south central to southeastern states in the USA. Sorghum fields in affected areas have sustained considerable losses. This aphid has also been reported on Johnsongrass and other feral grasses. The speed at which this aphid has spread raises serious concerns about future infestations. Many aphid species present genetically distinct populations when feeding on different host plants. Thus, it was hypothesized that the recent outbreak in sorghum could be explained by a recent introduction of a sorghum‐specialized genotype. In this study, we genetically characterized M. sacchari in three of its most common host plants – sorghum, sugarcane, and Johnsongrass – across its geographic distribution in the continental USA. Although M. sacchari specimens were grouped within three genetically distinct clusters, we did not find evidence of host plant or geographic population structure. Our characterization of the genetic structure of this pest provides baseline data aimed to help explain its recent outbreak in sorghum, as well as information that may aid in the design of sustainable control strategies.

Parent-parent and parent-offspring distances inSpondias radlkoferiseeds suggest long-distance pollen and seed dispersal: evidence from latrines of the spider monkey

Abstract:Pollen and seed dispersal are key ecological processes, directly impacting the spatial distribution, abundance and genetic structure of plant populations; yet, pollen- and seed-dispersal distances are poorly known. We used molecular markers to identify the parental origin (n = 152 adult trees) of 177Spondias radlkoferi(Anacardiaceae) seeds deposited by the spider monkey (Ateles geoffroyi) in latrines located beneath 17 sleeping-trees in two continuous forest sites (CF) and two forest fragments (FF) in the Lacandona rain forest, Mexico. We estimated mean parent-offspring (PO) distances per latrine and, for those seeds (54% of seeds) with more than one candidate parent (i.e. the potential maternal and parental parents), we also estimated parent-parent (PP) distances per latrine, and tested if PO and PP distances differed between forest types. Global PO and PP distances per latrine averaged 682 m (range = 83–1741 m) and 610 m (range = 74–2339 m), respectively, and did not differ significantly between CF and FF. This suggests that pollen dispersal is extensive in both forest types and that long seed dispersal distances (>100 m) are common, thus supporting the hypothesis that the spider monkey is an effective seed disperser ofS. radlkoferiin continuous and fragmented forests.

Composition, Population Structure and Regeneration of Rhododendron arboreum Sm. Temperate Broad-Leaved Evergreen Forest in Garhwal Himalaya, Uttarakhand, India

The present studied was carried out in four districts of Garhwal Himalaya. Survey and sampling of vegetation were completed used standard ecological method with aim to study of plant composition, population structure and regeneration at different site in the four districts viz. Pauri, Rudrapryag, Tehri and Chamoli of Garhwal Himalaya. Each district represents two sites, falls an altitude in Pauri (1850-2070 m), Rudrapryag (1775-2147 m), Tehri (1938–2459 m) and Chamoli (1711–1960 m). Among the altitudes over all range is (1711-2459 m) altitudes in all eight sites, total 16 tree species has been recorded. Total tree density varies from 670-1510 Ind ha-1, total seedling density from 220-1540 Ind ha-1 and total sapling density 165-1300 Ind ha-1 was recorded in all sites among the attitudes. Species diversity (H-) was observed between 0.12-0.19 for trees, 0.04-0.40 for seedling and 0.07-0.15 for sapling in all sites among the attitudes.

Studying of Plants Populations in the Conditions of Industrial Pollution in the Neighborhood of the Cities of the Karaganda Region

Objective In the article the results of studying of structure of plant populations are given in the neighborhood of the industrial cities of Temirtau, Balkhash, Zhezkazgan and in adjacent territories. Methods Field researches were conducted route-recognostic and semiportable methods. For each vegetable community established full floristic structure, determined phases of phenological development of separate species, their vital state, abundance (by a scale of Drudae), placement, morphometric parameters (height, development). Population density was estimated on the basis of data on a projective covering of vegetation. The age structure of communities we studied with application of methodological recommendations of R. Rabotnov. Reference of plants to this or that age state - based on a complex of qualitative morphological features the fresh and herbarizated plants. Results It has defined that round the industrial cities there is a loss longterm long vegetative elements, the share the ruderal grassy oneyear elements increases. Conclusion The carried-out analysis of a ratio a bio morph showed considerable changes and in the ratio trees, bushes, semi-low shrubs, grassy perennials and annual and biennial plants

Clonal structure and high genetic diversity at peripheral populations of Sorbus torminalis (L.) Crantz.

Abstract: Knowing the level of genetic diversity and structure in marginal plant populations is essential for managing their genetic resources. This is particularly important for rare scattered tree species, such as Sorbus torminalis (L.) Crantz. We investigated the genetic diversity and its spatial distribution in peripheral populations of S. torminalis. As the species is known to reproduce vegetatively, we also evaluated clonal structure within populations. Using 13 nuclear microsatellite loci designed in two multiplexes, we genotyped 172 individuals revealing the existence of 100 distinct genotypes. Number of ramets per genotype was variable across populations with an average of 1.72. Examples of somaclonal variation at particular loci were detected. Measures of genetic diversity of the total sample were relatively high (mean allelic richness AR = 10.293; expected heterozygosity He = 0.756), as compared to other S. torminalis populations. We noticed a slightly negative inbreeding coefficient (FIS = -0.029) indicating a small excess of heterozygotes, which is typical for self-incompatible plants. Genetic differentiation among populations was low (FST = 0.048), but Bayesian clustering methods revealed the existence of three distinct genetic clusters only in part related to population structure. Significant spatial genetic structure within populations was also detected (Sp = 0.0125) indicating fine-scale pattern of isolation by distance. Our study demonstrated that peripheral populations of S. torminalis may exhibit relatively high levels of genetic diversity despite the existence of vegetative propagation. Nevertheless, if the studied or similar populations are expected to be utilized as seed sources for ex-situ or in-situ conservation purposes, the existence of clonal structure and spatial genetic structure must be taken into account in order to avoid excessive sampling of the same or closely related genets.

Germination requirements and the influence of buffelgrass invasion on a population of Mammillaria grahamii in the Sonoran Desert

Buffelgrass invasion in the Sonoran Desert affects the regeneration of plant species and the diversity of plant communities. To study the impact of buffelgrass (Cenchrus ciliaris) invasion on the cactus Mammillaria grahamii, we compare density, population structure and association with nurse plants between an undisturbed natural site and an adjacent buffelgrass invaded site, in the Sonoran desert, Mexico. As germination and establishment are important phases determining species survival, we also studied germination requirements of M. grahamii seeds under controlled conditions. Five 5 × 20 m plots were used to compare plant cover, density, population structure and association in each site. A total of 128 individuals in 500 m2 were found in the natural area; 33 were in open areas and 95 under trees. About 71% of individuals under canopies were associated with two nurse species. In the invaded area 7 individuals were found under trees. M. grahamii seeds required light for germination, water potentials higher than - 0.6 MPa and temperatures above 25 °C. Seeds do not germinate after one minute exposure ≥100 °C. Results suggest that buffelgrass invasion affect cacti populations by changing the structure of a desert scrub, burning native plants, decreasing nurse plants, tree cover and changing microclimate.

Effects of density dependence in a temperate forest in northeastern China.

Negative density dependence may cause reduced clustering among individuals of the same species, and evidence is accumulating that conspecific density-dependent self-thinning is an important mechanism regulating the spatial structure of plant populations. This study evaluates that specific density dependence in three very large observational studies representing three successional stages in a temperate forest in northeastern China. The methods include standard spatial point pattern analysis and a heterogeneous Poisson process as the null model to eliminate the effects of habitat heterogeneity. The results show that most of the species exhibit conspecific density-dependent self-thinning. In the early successional stage 11 of the 16 species, in the intermediate successional stage 18 of the 21 species and in the old growth stage all 21 species exhibited density dependence after removing the effects of habitat heterogeneity. The prevalence of density dependence thus varies among the three successional stages and exhibits an increase with increasing successional stage. The proportion of species showing density dependence varied depending on whether habitat heterogeneity was removed or not. Furthermore, the strength of density dependence is closely related with species abundance. Abundant species with high conspecific aggregation tend to exhibit greater density dependence than rare species.

Reduced fine-scale spatial genetic structure in grazed populations of Dianthus carthusianorum.

Strong spatial genetic structure in plant populations can increase homozygosity, reducing genetic diversity and adaptive potential. The strength of spatial genetic structure largely depends on rates of seed dispersal and pollen flow. Seeds without dispersal adaptations are likely to be dispersed over short distances within the vicinity of the mother plant, resulting in spatial clustering of related genotypes (fine-scale spatial genetic structure, hereafter spatial genetic structure (SGS)). However, primary seed dispersal by zoochory can promote effective dispersal, increasing the mixing of seeds and influencing SGS within plant populations. In this study, we investigated the effects of seed dispersal by rotational sheep grazing on the strength of SGS and genetic diversity using 11 nuclear microsatellites for 49 populations of the calcareous grassland forb Dianthus carthusianorum. Populations connected by rotational sheep grazing showed significantly weaker SGS and higher genetic diversity than populations in ungrazed grasslands. Independent of grazing treatment, small populations showed significantly stronger SGS and lower genetic diversity than larger populations, likely due to genetic drift. A lack of significant differences in the strength of SGS and genetic diversity between populations that were recently colonized and pre-existing populations suggested that populations colonized after the reintroduction of rotational sheep grazing were likely founded by colonists from diverse source populations. We conclude that dispersal by rotational sheep grazing has the potential to considerably reduce SGS within D. carthusianorum populations. Our study highlights the effectiveness of landscape management by rotational sheep grazing to importantly reduce genetic structure at local scales within restored plant populations.

Microsatellite genetic diversity and mating systems in the columnar cactus Pachycereus pringlei (Cactaceae)

Mating systems and long-term climatic fluctuations have large impact on genetic diversity and population structure of plants; however, the genetic consequences have been poorly documented in species with geographic variation in mating systems. Here we used genetic variation from microsatellite markers to investigate the biogeographic pattern of Pachycereus pringlei, a columnar cactus with exceptional assortment of mating systems and wide range of distribution in the Sonoran Desert. Bayesian and multivariate analyses distinguished five genetic populations associated with differences in mating systems. Two hermaphroditic populations restricted to Cerralvo and Catalana islands were highly differentiated (ΦPT=0.26 and 0.21, respectively). Cerralvo Island showed the lowest genetic diversity (HO=0.26). Two other populations showed wide geographical distribution: a mostly gynodioecious population in the North comprising mostly hermaphrodite and female individuals, and a trioecious population in the South comprising unisexual and hermaphrodite individuals. The latter population exhibited the lowest level of genetic differentiation (ΦPT=0.14) and highest genetic diversity (HO=0.45). Cabo San Lucas, another trioecious population restricted to the southern end of the Baja California Peninsula, exhibits prevalence of unisexual individuals (0.76) but highly differentiated (ΦPT=0.19) and relatively moderate genetic diversity (HO=0.38). Latitudinal decrease of genetic diversity and isolation by distance supports northwards range expansion and southern BCP refugia, while Ecological Niche Models supported suitable climatic conditions during the Last Glacial Maximum in this region. These results suggest that the current biogeographic pattern of P. pringlei has been driven by longstanding climatic fluctuations associated with differential colonization abilities of genders and geographic variation of selfing and outcrossing rates. In conclusion, P. pringlei is not a panmictic assemblage and the interaction of historical vicariance and dispersal processes with mating systems may well explain present-day patterns of genetic variation.

In an arid urban matrix, fragment size predicts access to frugivory and rain necessary for plant population persistence

AbstractCities annex wilderness and alter the interactions between the plant and animal assemblages embedded in the remaining nature fragments. Here, we explore consequences of habitat fragmentation for dispersal of cactus by fruit‐eating mammals in the Sonoran Desert landscape. We use the barrel cactus, Ferocactus wislizeni, as a model system to diagnose (1) how fruit utilization by a mammal assemblage changes with fragment area and isolation, (2) what characteristics make individual plants particularly susceptible to frugivore failure, and (3) how inter‐fragment differences in plant–frugivore interactions influence the seedlings’ susceptibility to other stressors (granivores and drought). We described the type and phenology of plant–animal interactions in 20 fragments along a 0.05–500 ha size continuum within a large city (Tucson, Arizona, USA), and combined allometric scaling models of mammalian home ranges and descriptions of plant size distributions to predict the fraction of the fruit crops accessible to resident mammalian frugivores in each fragment. Fruit removal rates generally increased along a continuum of fragment sizes, and older, taller plants were particularly susceptible to frugivore failure and more likely to have fruits attacked by granivorous rodents. As a result, thresholds where the nature and/or phenology of a plant's interactions with animals changes can be accurately predicted by integrating descriptions of fragment size, fragment isolation, and plant population structure. Last, we found support for the hypothesis that fragmentation‐induced changes in the phenology of fruit removal compromise the seedlings’ ability to exploit precipitation delivered in winter and spring. Specifically, as a result of slower fruit removal, the seed crops in small fragments forfeit access to an increasing proportion of the rains between October and March, which determine whether cactus seedlings can survive the following dry season (April, May, June). We expect these inter‐site differences in the type and phenology of interactions to compromise the integrity of plant populations in smaller fragments, to become increasingly influential in ecological settings in the Sonoran Desert where access to precipitation is essential, and to become increasingly prevalent as the plants in newly fragmented plant populations age (grow) to sizes that are more susceptible to frugivore failure in the defaunated landscapes.

Impact of logging activities in a tropical mangrove on ecosystem diversity and sediment heavy metal concentrations

Productivity of mangrove ecosystems is compromised by anthropogenic activities including over-exploitation of wood. This study set out to understand how different wood harvesting regimes have affected the biodiversity of a tropical ecosystem and to identify relationships between the heavy metal concentrations in the mangrove sediments and tree felling. Soil samples were collected and plant diversity studies carried out on seven sites in the mangrove. Physico-chemical, chemical and mineralogical analyses were done on soil samples and plant population structure, species richness, evenness and diversity index at these sites were calculated. Results showed that soils across sites were characteristically clayey and acidic, with high organic matter content. Minerals identified included quartz, gibbsite, goethite, hematite and kaolinite. Heavy metal concentrations were higher in Sites 6 and 7 with a longer history of anthropogenic activity. There were strong negative correlations between the duration of logging and NO3-N (r = −0.838, p = 0.019), total N (r = −0.837, p = 0.019), NH4 +-N (r = −0.844, p = 0.017), Mg = (−0.789, p = 0.035), K (r = −0.819, p = 0.024), and Na (r = −0.988, p = 0.002). Sites which had experienced logging for longer periods (sites 3, 6, and 7) had lower nutrient content and lower values for species richness and diversity index. Logging in mangrove ecosystems could alter soil characteristics, decreasing plant diversity and abundance. Logging dynamics around mangrove ecosystems should be considered in the wider strategy for management and conservation of similar mangrove ecosystems.

Evolutionary Metabolomics Reveals Domestication-Associated Changes in Tetraploid Wheat Kernels.

Domestication and breeding have influenced the genetic structure of plant populations due to selection for adaptation from natural habitats to agro-ecosystems. Here, we investigate the effects of selection on the contents of 51 primary kernel metabolites and their relationships in three Triticum turgidum L. subspecies (i.e., wild emmer, emmer, durum wheat) that represent the major steps of tetraploid wheat domestication. We present a methodological pipeline to identify the signature of selection for molecular phenotypic traits (e.g., metabolites and transcripts). Following the approach, we show that a reduction in unsaturated fatty acids was associated with selection during domestication of emmer (primary domestication). We also show that changes in the amino acid content due to selection mark the domestication of durum wheat (secondary domestication). These effects were found to be partially independent of the associations that unsaturated fatty acids and amino acids have with other domestication-related kernel traits. Changes in contents of metabolites were also highlighted by alterations in the metabolic correlation networks, indicating wide metabolic restructuring due to domestication. Finally, evidence is provided that wild and exotic germplasm can have a relevant role for improvement of wheat quality and nutritional traits.

What causes conspecific plant aggregation? Disentangling the role of dispersal, habitat heterogeneity and plant–plant interactions

Spatial patterns of plant species are determined by an array of ecologica factors including biotic and abiotic environmental constraints and intrinsic species traits. Thus, an observed aggregated pattern may be the result of short‐distance dispersal, the presence of habitat heterogeneity, plant–plant interactions or a combination of the above. Here, we studied the spatial pattern of Mediterranean alpine plant Silene ciliata (Caryophyllaceae) in five populations and assessed the contribution of dispersal, habitat heterogeneity and conspecific plant interactions to observed patterns. For this purpose, we used spatial point pattern analysis combined with specific a priori hypotheses linked to spatial pattern creation. The spatial pattern of S. ciliata recruits was not homogeneous and showed small‐scale aggregation. This is consistent with the species’ short‐distance seed dispersal and the heterogeneous distribution of suitable sites for germination and establishment. Furthermore, the spatial pattern of recruits was independent of the spatial pattern of adults. This suggests a low relevance of adult‐recruits interactions in the spatial pattern creation. The difference in aggregation between recruits and adults suggests that once established, recruits are subjected to self‐thinning. However, seedling mortality did not erase the spatial pattern generated by seed dispersal, as S. ciliata adults were still aggregated. Thus, the spatial aggregation of adults is probably due to seed dispersal limitation and the heterogeneous distribution of suitable sites at seedling establishment rather than the presence of positive plant–plant interactions at the adult stage. In fact, a negative density‐dependent effect of the conspecific neighbourhood was found on adult reproductive performance. Overall, results provide empirical evidence of the lack of a simple and direct relationship between the spatial structure of plant populations and the sign of plant–plant interactions and outline the importance of considering dispersal and habitat heterogeneity when performing spatial analysis assessments.