Spatial and temporal distribution of chloroplast DNA polymorphism in a tropical tree species

The level and the spatial organization of chloroplast DNA polymorphism were investigated in Dicorynia guianensis Hamshoff (Caesalpiniaceae) at different spatial and temporal scales. D. guianensis is a canopy tree of the rain forest that is distributed throughout the Guiana plateau in small aggregates. Twelve different haplotypes were identified using restriction analysis of polymerase chain reaction (PCR) amplified fragments of the chloroplast genome. When populations from different areas of French Guiana were compared, a clear geographical pattern of haplotype frequencies was identified along the Atlantic coast. This pattern is most likely the result of the restriction-expansion dynamics of the tropical forest during the Quaternary. At the local level, D. guianensis was characterized by a high level of within population diversity. Maintenance of within population diversity results from the dynamics of the aggregates; stochastic demography associated with the turnover of aggregates generates genetic differentiation among them. At the stand level, a strong spatial aggregation of haplotypes persisted from the adult to the seedling cohort indicating limited seed flow. There was also a strong difference in levels of diversity between the cohorts which suggested that recruitment over several years is needed in order to maintain genetic diversity during regeneration.     

Impact of selective logging on inbreeding and gene dispersal in an Amazonian tree population of Carapa guianensis Aubl

Selective logging may impact patterns of genetic diversity within populations of harvested forest tree species by increasing distances separating conspecific trees, and modifying physical and biotic features of the forest habitat. We measured levels of gene diversity, inbreeding, pollen dispersal and spatial genetic structure (SGS) of an Amazonian insect-pollinated Carapa guianensis population before and after commercial selective logging. Similar levels of gene diversity and allelic richness were found before and after logging in both the adult and the seed generations. Pre- and post-harvest outcrossing rates were high, and not significantly different from one another. We found no significant levels of biparental inbreeding either before or after logging. Low levels of pollen pool differentiation were found, and the pre- vs. post-harvest difference was not significant. Pollen dispersal distance estimates averaged between 75 m and 265 m before logging, and between 76 m and 268 m after logging, depending on the value of tree density and the dispersal model used. There were weak and similar levels of differentiation of allele frequencies in the adults and in the pollen pool, before and after logging occurred, as well as weak and similar pre- and post-harvest levels of SGS among adult trees. The large neighbourhood sizes estimated suggest high historical levels of gene flow. Overall our results indicate that there is no clear short-term genetic impact of selective logging on this population of C. guianensis.     

Population structure delineated with microsatellite markers in fragmented populations of a tropical tree, carapa guianensis (Meliaceae)

Deforestation and selective logging in the tropics may have serious consequences on genetic processes in tropical tree populations, affecting long-term survival of a given species as well as tropical forest communities. Because understanding the effects of human-induced changes on genetic processes is of utmost importance in formulating sound conservation and management plans for tropical forest communities, we developed microsatellite or simple sequence repeat (SSR) markers for the tropical tree Carapa guianensis (Meliaceae) and assessed the polymorphism of SSRs in adult and sapling populations in a large contiguous forest and in selectively logged and fragmented forests. The number of alleles in polymorphic loci ranged between 4 and 28. No inbreeding was detected in saplings or adult cohorts, but the allelic richness was lower in the sapling cohort of the isolated fragment. Genetic distances, Nei's D and (delta&mgr;)2, and RST values among saplings were greater than among adult cohorts, suggesting restriction of gene flow due to deforestation and habitat fragmentation. These SSR loci may be used to address many related questions regarding the population and conservation genetics of tropical trees.     

Genetic diversity,spatial genetic structure and realised seed and pollen dispersal of Himatanthus drasticus (Apocynaceae) in the Brazilian savanna

We assessed the pollen and seed dispersal patterns, genetic diversity, inbreeding and spatial genetic structure of Himatanthus drasticus (Apocynaceae), a tree native to the Brazilian Savanna (Cerrado) that is heavily exploited for its medicinal latex. The study was conducted in the Araripe National Forest, Ceará State, Brazil. Within a one-hectare plot, samples were collected from all adult trees, adult trees located in the immediate vicinity of the plot, and seedlings. All sampled individuals were mapped and genotyped using microsatellite markers. High levels of polymorphism and significant levels of inbreeding were found, which indicates that self-fertilisation and mating among relatives occur in this population. Both the adults and seedlings had significant spatial genetic structure up to ~40 m and our results confirmed the occurrence of isolation by distance. Pollen and seeds were dispersed over short distances and immigration of pollen and seeds into the plot was estimated at 13 and 9 %, respectively. Taking into consideration the degree of inbreeding, relatedness, intrapopulation spatial genetic structure and pollen dispersal distance, we recommend collecting seeds from a large number of trees spaced at least 150 m apart to avoid collecting seeds from related individuals and an overlap of pollen pools among seed trees.     

Long‐distance pollen and seed dispersal and inbreeding depression in Hymenaea stigonocarpa (Fabaceae: Caesalpinioideae) in the Brazilian savannah

Hymenaea stigonocarpa is a neotropical tree that is economically important due to its high‐quality wood; however, because it has been exploited extensively, it is currently considered threatened. Microsatellite loci were used to investigate the pollen and seed dispersal, mating patterns, spatial genetic structure (SGS), genetic diversity, and inbreeding depression in H. stigonocarpa adults, juveniles, and open‐pollinated seeds, which were sampled from isolated trees in a pasture and trees within a forest fragment in the Brazilian savannah. We found that the species presented a mixed mating system, with population and individual variations in the outcrossing rate (0.53–1.0). The studied populations were not genetically isolated due to pollen and seed flow between the studied populations and between the populations and individuals located outside of the study area. Pollen and seed dispersal occurred over long distances (>8 km); however, the dispersal patterns were isolated by distance, with a high frequency of mating occurring between near‐neighbor trees and seeds dispersed near the parent trees. The correlated mating for individual seed trees was higher within than among fruits, indicating that fruits present a high proportion of full‐sibs. Genetic diversity and SGS were similar among the populations, but offspring showed evidence of inbreeding, mainly originating from mating among related trees, which suggests inbreeding depression between the seed and adult stages. Selfing resulted in a higher inbreeding depression than mating among relatives, as assessed through survival and height. As the populations are not genetically isolated, both are important targets for in situ conservation to maintain their genetic diversity; for ex situ conservation, seeds can be collected from at least 78 trees in both populations separated by at least 250 m.     

Fine-scale genetic structure of the threatened rosewood Dalbergia nigra from the Atlantic Forest: comparing saplings versus adults and small fragment versus continuous forest

Assessing the population genetic structure of threatened species is important for developing successful conservation strategies. In this study, we evaluated the fine-scale spatial genetic structure (SGS) of Dalbergia nigra from a regenerating secondary forest fragment and compared it with previous data from a primary forest of a large reserve. A total of 107 adult and 111 saplings were mapped and genotyped for seven microsatellite loci. The genetic diversity was high and similar in adults (H _e?=?0.682) and saplings (H _e?=?0.680). The spatial extent of SGS was higher in adults than in saplings. Overlapping generations in the potentially reproductive individuals is the likely explanation for the higher SGS in adults (Sp?=?0.016) in relation to the saplings (Sp?=?0.010). The SGS in the adults from the secondary forest fragment was similar to that found in the primary forest. Considering the SGS found in adults, from both the secondary and primary forests, seeds for ex situ conservation should be collected from trees at least 80 m apart to reduce the genetic similarity between samples. These results highlight the importance of preserving small forest fragments to allow successful regeneration and maintenance of the genetic diversity in D. nigra.     

Effects of seed- and pollen-mediated gene dispersal on genetic structure among Quercus salicina saplings

We evaluated the effects of seed- and pollen-mediated gene dispersal on genetic structure among Quercus salicina saplings. Parentage analysis using 10 microsatellite markers indicated that the 111 adult trees located within a 11.56 ha plot in the Tatera Forest Reserve, Japan, included only one parent of 44.2% and both parents of 40.7% of the 226 saplings located in a 1-ha core plot at its center. Coancestry (F(ij)) estimates indicated that there was strong genetic structure among the saplings. The numbers of pairs of full- and half-siblings were high among neighboring saplings, suggesting that there was strong maternal half-sibling family structure among the saplings around their seed parents, probably generated by the spatially limited seed dispersal and the small extent of overlapping seed shadows owing to the low density of adults. The frequencies also suggest that the maternal half-sibling families are interspersed with full-siblings, produced by correlated mating, probably because pollination frequency depends on the distance between parents. The frequencies of pairs of half-siblings decreased as the distance between saplings increased, but did not fall to zero even at distances up to the 90-95 m class, suggesting that paternal half-siblings originating from correlated paternity were widely distributed owing to extensive pollen flow. We separately examined the genetic structure for maternal and paternal alleles in the saplings. Unsurprisingly, very strong genetic structure was detected for maternal alleles. However, weak (but significant) genetic structure was also detected for paternal alleles. Therefore, pollen dispersal may affect the extent of genetic structure as well as seed dispersal.     

Tree recovery and seed dispersal by birds: Comparing forest, agroforestry and abandoned agroforestry in coastal Ecuador

We used a highly replicated study to examine vegetation characteristics between patches of intervened forest, abandoned agroforestry systems with coffee and actively managed agroforestry systems with coffee in a tropical landscape. In all habitats, plant structural characteristics, individual abundance, species richness and composition were recorded for the three plant size classes: adult trees, saplings and seedlings. Furthermore, bird species richness and composition, and seeds dispersed by birds were recorded. Tree abundance was higher in forest habitats while saplings and seedlings were more abundant in abandoned coffee sites. Although species richness of adult trees was similar in the three habitats, species richness of saplings and seedlings was much higher in forest and abandoned coffee than in managed coffee sites. However, in spite of their relatively low species richness, managed coffee sites are an important refuge for tree species common to the almost disappeared mature forest in the area. Floristic similarity for adult trees was relatively low between land use types, but clearly higher for seedlings, indicating homogenizing processes at the landscape level. More than half of the saplings and seedling were not represented by adults in the canopy layer, suggesting the importance of seed dispersal by birds between habitats. Our results show that each of the studied ecosystems plays a unique and complementary role as seed source and as habitat for tree recovery and tree diversity.     

Spatial patterns and associations in a Quercus‐Betula forest in northern China

Question: Are species‐specific regeneration strategies and competition the dominant processes facilitating species coexistence in a Quercus liaotungensis dominated temperate deciduous forest? Location: Dongling Mountains, North China, 1300 m a.s.l. Methods: Ripley's K‐function was used to characterize the spatial patterns and spatial associations of two dominant tree species, Quercus liaotungensis and Betula dahurica, and a common subcanopy species, Acer mono, at different growth stages (adult, sapling, seedling). Results: Seedlings, saplings and adults of all three species exhibited clumped distributions at most spatial scales. Quercus seedlings and saplings were positively associated with conspecific adult trees and spatially independent of dead trees suggesting that seed dispersal and vegetative regeneration influenced the spatial patterning of Quercus trees. Betula seedlings and saplings were positively associated with both live and dead trees of conspecific adults at small scales (<5 m) but negatively associated with live and dead trees of other species indicating sprouting as an important mechanism of reproduction. Saplings of Acer had a strong spatial dependence on the distribution of conspecific adult trees indicating its limited seed dispersal range. Negative associations between adult trees of Betula and Quercus demonstrated interspecific competition at local scales (<5 m). Conclusions: Different regeneration strategies among the three species play an important role in regulating their spatial distribution patterns, while competition between individuals of Betula and Quercus at the adult stage also contributes to spatial patterning of these communities. The recruitment limitations of Betula and Quercus may affect the persistence of these species and the long‐term dynamics of the forest.     

Spatial genetic structure in wild cherry (Prunus avium L.): I. variation among natural populations of different density

Conservation of forest genetic resources requires intensive knowledge of the spatial arrangement of genetic diversity. In this study, we used four natural Prunus avium stands in Germany with contrasting for densities to understand patterns of spatial genetic structure. To this end, we genotyped adults and saplings at eight microsatellite markers, 54 AFLP loci and at the gametophytic incompatibility locus. We estimated levels of clonal propagation, spatial genetic structure and gene dispersal. High mortality occurred among young clonal individuals, as depicted by the lower clonal diversity in saplings. Contrasting levels of spatial genetic structure were observed among markers, ontogenic stages and populations. AFLP were more efficient for detecting spatial autocorrelation but did not allow us to differentiate low and high density populations, while high density populations showed substantially stronger spatial genetic structure at microsatellite loci. Furthermore, kinship decreased with tree age only in low density stands. We discuss the present results in terms of population history, pollen and seed dispersal and population density. Although conspecific density seems to be an interesting indicator of genetic diversity for conservation programmes, we still need to disentangle the relative influence of clonal propagation and density on the strength of spatial genetic structure. Simulation studies are needed to further address this question.     

Genetic and reproductive consequences of forest fragmentation for populations of <Emphasis Type="Italic">Magnolia obovata</Emphasis>

In order to evaluate the consequences of forest fragmentation on populations of Magnolia obovata, we compared genetic diversity and reproductive characteristics at two nearby sites, one conserved and one fragmented. The genetic diversity between adults trees of the different sites was not significantly different. However, saplings in the conserved site showed a significantly higher genetic diversity than both adult trees in the conserved site and saplings in the fragmented sites; this was found to be the result of the larger gene flow into the conserved site. The density of the adult trees was significantly related to all of the reproductive traits analyzed (fertilization of ovules, insect attack to seeds, ovules that developed into seeds and outcrossing at the stage of seeds) at both sites. At both sites, fertilization of ovules and insect attack on seeds were positively correlated to adult tree density while outcrossing rate was negatively correlated to adult tree density. The fertilization of ovules and outcrossing were more dependent on adult tree density in the fragmented site than in the conserved site. The probability of ovules developing into outcrossed seeds showed a negative correlation with adult tree density at both sites, indicating the advantage of low density for this species and possibly implying a resilience to habitat fragmentation. A two-generation-analysis did not identify significant differences between sites in terms of the structure of the pollen pool and the number of pollen donors. Although fragmentation affected reproductive characteristics, the effect on seedling establishment and subsequent survival remains to be determined. Proposals for future studies that will assist in the development of management strategies for forests suffering fragmentation are made.     

Linking seed dispersal and genetic structure of trees: a biogeographical approach

Aim Natural and human‐induced differences in frugivore assemblages can influence the seed dispersal distances of trees. An important issue in seed dispersal systems is to understand whether differences in seed dispersal distances also affect the genetic structure of mature trees. One possible approach to test for a relationship between seed dispersal and the genetic structure of mature trees is to compare the genetic structure of two closely related tree species between two biogeographical regions that differ in frugivore assemblages and seed dispersal distances. Previous studies on two Commiphora species revealed that Commiphora guillauminii in Madagascar has a much lower seed dispersal distance than Commiphora harveyi in South Africa. We tested whether the lower seed dispersal distance might have caused decreased gene flow, resulting in a stronger genetic structure in Madagascar than in South Africa. Location Madagascar and South Africa. Methods Using amplified fragment length polymorphism markers we investigated the genetic structure of 134 trees in Madagascar and 158 trees in South Africa at a local and a regional spatial scale. Results In concordance with our hypothesis, kinship analysis suggests that gene flow was restricted mostly to 3 km in Madagascar and to 30 km in South Africa. At the local spatial scale, the genetic differentiation among groups of trees within sample sites was marginally significantly higher in Madagascar (F_ST = 0.069) than in South Africa (F_ST = 0.021). However, at a regional spatial scale genetic differentiation was lower in Madagascar (F_ST = 0.053) than in South Africa (F_ST = 0.163). Main conclusions Our results show that lower seed dispersal distances of trees were linked to higher genetic differentiation of trees only at a local spatial scale. This suggests that seed dispersal affects the genetic population structure of trees at a local, but not at a regional, spatial scale.     

Patterns of pollen flow in a dense population of the insect-pollinated canopy tree species Castanopsis sieboldii

Insect pollinations of tree species with high-density populations have rarely been studied. Since the density of adults can affect effective pollen dispersal, short-distance pollination, even by insects, may frequently occur in high-density populations. To test this prediction, we investigated pollination patterns in a high-density population of the insect-pollinated canopy tree species Castanopsis sieboldii by paternity analysis using genotypes at 8 microsatellite loci of 145 adult trees and 439 seeds from 11 seed parents in a 4-ha plot. We then explored their genetic effects on the population by calculating other population genetics parameters. Although C. sieboldii has high potential for long-distance dispersal of pollen (as indicated by a fat-tailed dispersal kernel), the cumulative pollination at the local scale was spatially limited and strongly dependent on the distance between parents due to the high density of adults. Genetic diversity estimates for pollen pools accepted by each seed parent converged on a maximum as the effective number of pollen parents increased. The genetic diversity of pollen pool bulked over all the seed parents from inside the plot did not differ from that of the total pollen pools. Therefore, although pollen flow from distant pollen parents may help to maintain the genetic diversity of offspring, pollen parents neighboring seed parents may be the main contributors to the genetic diversity of the offspring at the seed stage.     

Microsatellite analysis of seed dispersal and parentage of saplings in bur oak, Quercus macrocarpa

Microsatellite analysis was used to examine parentage and spatial distributions of 62 adult bur oaks Quercus macrocarpa, and 100 saplings in a single stand. Using genotypes scored by PCR products at four microsatellite loci, we determined that 94 saplings matched at least one parent in the stand. Saplings often occur as dense clusters of half-sibs around the presumed maternal parent, and only four adults were seed parents to a large proportion of the saplings sampled. A stump apparently was the seed parent of the largest cluster of half-sibs, which occupied a sizeable light gap opened up by the death of their maternal tree. Approximately half of the saplings appeared to have grown from seeds that had not been removed after falling from the tree, and half from seeds that were dispersed beyond the crown of their maternal parent. Long-distance seed dispersal may be more common than has been previously reported. Extremely high levels of long-distance pollination were indicated, and pollen donors within the stand were generally distributed randomly around maternal trees. More than half of the saplings had paternal parents outside of the stand. This study demonstrates the utility of microsatellite analysis for studying mating systems, seed dispersal and seedling establishment in natural plant populations.     

Are all seeds equal? Spatially explicit comparisons of seed fall and sapling recruitment in a tropical forest

Understanding demographic transitions may provide the key to explain the high diversity of tropical tree communities. In a faunally intact Amazonian forest, we compared the spatial distribution of saplings of 15 common tree species with patterns of conspecific seed fall, and examined the seed-to-sapling transition in relation to locations of conspecific trees. In all species, the spatial pattern of sapling recruitment bore no resemblance to predicted distributions based on the density of seed fall. Seed efficiency (the probability of a seed producing a sapling) is strongly correlated with distance from large conspecific trees, with a >30-fold multiplicative increase between recruitment zones that are most distant vs. proximal to conspecific adults. The striking decoupling of sapling recruitment and conspecific seed density patterns indicates near-complete recruitment failure in areas of high seed density located around reproductive adults. Our results provide strong support for the spatially explicit predictions of the Janzen-Connell hypothesis.     

Fine‐scale Spatial Genetic Structure of Ten Dipterocarp Tree Species in a Bornean Rain Forest

Fine‐scale spatial genetic structure is increasingly recognized as an important factor in the studies of tropical forest trees as it influences genetic diversity of local populations. The biologic mechanisms that generate fine‐scale spatial genetic structure are not fully understood. We studied fine‐scale spatial genetic structure in ten coexisting dipterocarp tree species in a Bornean rain forest using microsatellite markers. Six of the ten species showed statistically significant fine‐scale spatial genetic structure. Fine‐scale spatial genetic structure was stronger at smaller spatial scales (≤ 100 m) than at larger spatial scales (> 100 m) for each species. Multiple regression analysis suggested that seed dispersal distance was important at the smaller spatial scale. At the larger scale (> 100 m) and over the entire sample range (0–1000 m), pollinators and spatial distribution of adult trees were more important determinants of fine‐scale spatial genetic structure. Fine‐scale spatial genetic structure was stronger in species pollinated by less mobile small beetles than in species pollinated by the more mobile giant honeybee (Apis dorsata). It was also stronger in species where adult tree distributions were more clumped. The hypothesized mechanisms underlying the negative correlation between clump size and fine‐scale spatial genetic structure were a large overlap among seed shadows and genetic drift within clumped species.     

Is farther seed dispersal better? Spatial patterns of offspring mortality in three rainforest tree species with different dispersal abilities

The paradigm that tropical trees with farther seed dispersal experience lower offspring mortality is currently based on within-species studies documenting higher survival of offspring located farther from conspecific adults and/or closer to light gaps. We determined whether the paradigm also holds among species by comparing spatial patterns of offspring mortality among three sympatric Neotropical rainforest tree species with the same seed dispersers but with different dispersal abilities. First, we assessed spatially non-random mortality for each species by measuring spatial shifts of the population recruitment curve (PRC) with respect to conspecific adults and light gaps across three early life stages: dispersed seeds, young seedlings and old seedlings. Then, we determined whether PRC shifts were greater for the species with short dispersal distances than for the species with greater dispersal distances. We found that the PRC shifted away from conspecific adults consistently across life stages, but we found no consistent PRC shifts towards gaps, suggesting that mortality was related more to the proximity of conspecifics than to absence of light gaps. PRC shifts away from adults were greatest in the species with the lowest dispersal ability, supporting the paradigm. Differential PRC shifts caused the spatial distribution of offspring to become almost independent with respect to adult trees and gaps in all three species, despite large differences in seed dispersal distance among these species. Our results provide direct empirical support for the paradigm that among tropical trees, species with farther seed dispersal are less impacted by spatially non-random mortality than are similar species with shorter dispersal distances. Thus, greater dispersal effectiveness merits extra investments of trees in seed dispersal ability, even at the cost of fecundity.     

Assessment of spatial discordance of primary and effective seed dispersal of European beech (Fagus sylvatica L.) by ecological and genetic methods

Spatial discordance between primary and effective dispersal in plant populations indicates that postdispersal processes erase the seed rain signal in recruitment patterns. Five different models were used to test the spatial concordance of the primary and effective dispersal patterns in a European beech (Fagus sylvatica) population from central Spain. An ecological method was based on classical inverse modelling (SSS), using the number of seed/seedlings as input data. Genetic models were based on direct kernel fitting of mother‐to‐offspring distances estimated by a parentage analysis or were spatially explicit models based on the genotype frequencies of offspring (competing sources model and Moran‐Clark's Model). A fully integrated mixed model was based on inverse modelling, but used the number of genotypes as input data (gene shadow model). The potential sources of error and limitations of each seed dispersal estimation method are discussed. The mean dispersal distances for seeds and saplings estimated with these five methods were higher than those obtained by previous estimations for European beech forests. All the methods show strong discordance between primary and effective dispersal kernel parameters, and for dispersal directionality. While seed rain was released mostly under the canopy, saplings were established far from mother trees. This discordant pattern may be the result of the action of secondary dispersal by animals or density‐dependent effects; that is, the Janzen‐Connell effect.     

Fine-scale genetic dynamics of a dominant neotropical tree in the threatened Brazilian Atlantic Rainforest

We present a case study of the relationship between spatial genetic structure (SGS) and age structure in Protium spruceanum (Burseraceae), an insect-pollinated, mass-fruiting, and secondary bird-dispersed tree, as determined through variation in allozyme loci. Using ten polymorphic loci, we investigated spatial and temporal patterns of a genetic structure within a 40?m?×?60?m plot in a small (1.0?ha) fragment of Atlantic Rainforest to investigate the processes shaping the distribution of genetic diversity. Individuals (n?=?345) from seedlings to adults were grouped and analyzed in four diameter classes. The results showed a high average level of genetic diversity (H _e?=?0.438), but genetic diversity parameters did not vary significantly among cohorts. The spatial distribution pattern analysis of individuals showed significant levels of aggregation among small- and medium-diameter classes and random distribution among the highest diameter class, likely due to processes of competitive thinning. There was an association between demographic and SGS at short distances (less than 10?m) which is likely the consequence of restricted seed dispersal. The degree of SGS decreased across small- to large-diameter classes. We inferred that limited seed dispersal and subsequent density-dependent mortality from the family clusters are responsible for the observed changes in fine-scale SGS across different demographic classes.     

Different age and spatial structure of two spontaneous subpopulations of Taxus baccata as a result of various intensity of colonization process

The aim of the present work was a comparison of the age and spatial structure of two populations of Taxus baccata in the Kórnik Arboretum, formed spontaneously under different initial conditions. The first of them (plot one) comes from at least 11, while the second (plot two) from only two, potential mother tress at a distance up to about 100 m. The influence of the local climate conditions on the seedlings was also analyzed.Age structure of the population formed from 11 mother trees was found to be typical for young, but developing populations of shade tolerant trees about 40 years after the first cohorts were founded. The youngest seedlings formed the most numerous age class, still without saplings. The class ranking next consisted of tree-like specimens of the highest age. Obviously, the population of the first plot was formed by only few cohorts of seeds, in period of about 20 years. Seedlings may have appeared every year, but most often nearly all of them died. The sub-population on the second plot, developed as offspring from only two close-by growing mother trees, was formed during much a longer period and is characterized by a different age structure. The oldest individuals are less numerous as those in sub-population one. There is also a number of saplings, which are still joining the main stand; such saplings were not found in the other sub-population. The spatial structure of two sub-populations is also different. The first of them, which comes from several mother trees, is characterized as rather uniform, while the second which can be traced back to two mother trees, shows a clump distribution of tree-like yews.The climate parameter limiting the number of surviving seedlings in particular years appears to be a minimal temperature below −7.5 °C in November. Temperatures of winter and spring, as well as the drought/precipitation regime during the vegetation period do not restrict the survival rate of the seedlings.Obviously, the distribution of individuals of the ornithochoric species T. baccata is strongly determined by the availability of mother trees in a distance suitable to be bridged by birds. Long distances limit seed supply heavily and retard and prolong the period of colonization. As a consequence, dispersal distances influence strongly age and spatial structure of cohorts founded from isolated (groups of) mother trees.