Oaks (Quercus) are major components of temperate forest ecosystems in the Northern Hemisphere where they form intermediate or climax communities. Sessile oak (Quercus petraea) forests represent the ...climax vegetation in eastern Germany and western Poland. Here, sessile oak forms pure stands or occurs intermixed with Scots Pine (Pinus sylvestris). A large body of research is available on gene flow, reproduction dynamics, and genetic structure in fragmented landscapes and mixed populations. At the same time, our knowledge regarding large, contiguous, and monospecific populations is considerably less well developed. Our study is an attempt to further develop our understanding of the reproduction ecology of sessile oak as an ecologically and economically important forest tree by analyzing mating patterns and genetic structure within adult trees and seedlings originating from one or two reproduction events in an extensive, naturally regenerating sessile oak forest. We detected positive spatial genetic structure up to 30 meters between adult trees and up to 40 meters between seedlings. Seed dispersal distances averaged 8.4 meters. Pollen dispersal distances averaged 22.6 meters. In both cases, the largest proportion of the dispersal occurred over short distances. Dispersal over longer distances was more common for pollen but also appeared regularly for seeds. The reproductive success of individual trees was highly skewed. Only 41 percent of all adult trees produced any offspring while the majority did not participate in reproduction. Among those trees that contributed to the analyzed seedling sample, 80 percent contributed 1–3 gametes. Only 20 percent of all parent trees contributed four or more gametes. However, these relatively few most fertile trees contributed 51 percent of all gametes within the seedling sample. Vitality and growth differed significantly between reproducing and nonreproducing adult trees with reproducing trees being more vital and vigorous than nonreproducing individuals. Our study demonstrates that extensive, apparently homogenous oak forests are far from uniform on the genetic level. On the contrary, they form highly complex mosaics of remarkably small local neighborhoods. This counterbalances the levelling effect of long‐distance dispersal and may increase the species’ adaptive potential. Incorporating these dynamics in the management, conservation, and restoration of oak forests can support the conservation of forest genetic diversity and assist those forests in coping with environmental change.
Extensive, apparently homogenous oak forests are far from uniform on the genetic level. On the contrary, they form highly complex mosaics of remarkably small local neighborhoods. This counterbalances the levelling effect of long‐distance dispersal and may increase the species’ adaptive potential. Incorporating these dynamics into the management, conservation, and restoration of oak forests can support the conservation of forest genetic diversity and assist those forests in coping with environmental change.
In Germany, Douglas fir (
Pseudotsuga menziesii
Franco) is seen as a valuable species for future cultivation in times of climate change. Local seed production in seed stands and seed orchards may ...secure that local adaptation is transferred to the next generation, but small population sizes could lower genetic diversity and thus future adaptability. Here we analyse the transfer of genetic diversity from parent to offspring generation in four older German seed orchards. We detected low pollen contamination rates due to high levels of spatial isolation. Even with a relatively low number of 40 clones, seed orchard design with randomized and repeated planting of clones led to low selfing rates, and despite uneven parental contributions, the number of successful parents and the level of genetic intermixture were high enough to allow the transfer of an adequate part of the genetic diversity to the next generation. Larger numbers, however, might be needed to reliably conserve the entire genetic diversity over succeeding generations. Conclusions on the establishment of future seed orchards and regarding areas requiring further research are drawn at the end of the paper.
This paper introduces a new approach-the Principal Component Gradient Analysis (PCGA)-to detect ecological gradients in time-series populations, i.e. several time-series originating from different ...individuals of a population. Detection of ecological gradients is of particular importance when dealing with time-series from heterogeneous populations which express differing trends. PCGA makes use of polar coordinates of loadings from the first two axes obtained by principal component analysis (PCA) to define groups of similar trends. Based on the mean inter-series correlation (rbar) the gain of increasing a common underlying signal by PCGA groups is quantified using Monte Carlo Simulations. In terms of validation PCGA is compared to three other existing approaches. Focusing on dendrochronological examples, PCGA is shown to correctly determine population gradients and in particular cases to be advantageous over other considered methods. Furthermore, PCGA groups in each example allowed for enhancing the strength of a common underlying signal and comparably well as hierarchical cluster analysis. Our results indicate that PCGA potentially allows for a better understanding of mechanisms causing time-series population gradients as well as objectively enhancing the performance of climate transfer functions in dendroclimatology. While our examples highlight the relevance of PCGA to the field of dendrochronology, we believe that also other disciplines working with data of comparable structure may benefit from PCGA.
Plant-associated mycobiomes in extreme habitats are understudied and poorly understood.
We analysed Illumina-generated ITS1 sequences from the needle mycobiome of white spruce (Picea glauca) at the ...northern treeline in Alaska (USA). Sequences were obtained from the same DNA that was used for tree genotyping. In the present study, fungal metabarcoding and tree microsatellite data were compared for the first time.
In general, neighbouring trees shared more fungal taxa with each other than trees growing in further distance. Mycobiomes correlated strongly with phenological host traits and local habitat characteristics contrasting a dense forest stand with an open treeline site. Genetic similarity between trees did not influence fungal composition and no significant correlation existed between needle mycobiome and tree genotype.
Our results suggest the pronounced influence of local habitat conditions and phenotypic tree traits on needle-inhabiting fungi. By contrast, the tree genetic identity cannot be bench-marked as a dominant driver for needle-inhabiting mycobiomes, at least not for white spruce in this extreme environment.
•Evaluation of different sized approved Douglas-fir seed stands in Germany.•Improvement of the quality of forest reproductive material.•Selfing rate increased in correlation with inbreeding ...effects.•The loss of alleles at descending size cannot be compensated by pollen from outside.•The basic requirements should be adapted for approved seed stands in Germany.
Douglas-fir (Pseudotsuga menziesii), native to western North America, was introduced to Europe about 150 years ago. Nowadays it represents the most frequent non-native forest tree species in Germany, covering about 2% of the forest area. While seeds were initially imported from its natural distribution range, the German seed market is now mainly supplied with seeds from local stands. In this study we examined four representative, different sized artificial Douglas-fir stands. We used microsatellite markers to characterise adults and offspring by analysing the genetic diversity and mating system. We detected a negative correlation of population size and genetic diversity. The loss of alleles with descending population sizes cannot be compensated by pollen from outside of the stand. The results showed an increased selfing rate (1–13%) correlated with increased inbreeding effects like a high percentage of empty seeds. Diversity parameters calculated as averages across the analysed loci should always be completed with the calculation of effective population sizes considering sibship structures based on multilocus genotypes. The combined approaches are an improved basis for drawing practical conclusions. We recommend that the current regulations for forest reproductive material should be adapted. For wind-pollinated stand-forming tree species a minimum number of 100 adult trees should be required to form approved seed stands in the category “Selected”.
Abstract Metabarcoding is emerging as an alternative to morphological methods in noninvasive carnivore diet analysis based on scats. A number of metabarcoding markers have been developed but their ...comparative performance to recover DNA from scats remains mostly untested. We tested three markers covering a wide taxonomic range of prey items and compared them with the results of a morphological analysis. Morphological and genetic methods performed comparably regarding the identity of detected prey species, but the number of identified species varied strongly between markers. Only one, 12S-V5, amplified successfully in all samples and proved to be robust and reliable when working with the highly degraded DNA obtained from scats.
Eighteen microsatellite primer pairs previously developed at Oak Ridge National Laboratory for Populus tremuloides Michx. and Populus trichocarpa Tort. ＆ Gray were screened for amplification in ...Euphrates poplar, Populus euphratica Oliv. Thirteen loci were found to express polymorphisms ranging from two to 17 alleles. The eight most variable loci were selected to set up and optimize two multiplex polymerase chain reaction （PCR） assays. Three populations containing altogether 436 trees were used to characterize the selected loci and ascertain their applicability for parentage analysis and genotyping studies. Through cross-checking of clonal identity against sex of the genotyped trees we estimated the maximum error rate for merging genotypes to be less than 0.045.
Adult individuals and seeds of two mixed stands of coastal and interior Douglas-fir (
Pseudotsuga menziesii
(Mirb.) Franco) were analysed for genetic differentiation between the two varieties and ...evidence of intervarietal pollination. Clear genetic discrimination between the two varieties was observed based on multilocus evaluation of nine microsatellite markers using other Douglas-fir stands of known variety composition for comparison. Analysis of pollination distances showed that 80% of pollinations took place within a distance of about 44–55 m. Analysis of stand structure showed clearly separated areas of mainly coastal or interior Douglas-fir within both stands. Together with short pollination distances this led to an apparent dominance of intravarietal pollinations. However, analysis of pollination partners of trees growing near the border of the variety specific areas, does not indicate the existence of reproductive barriers between trees of the two varieties growing in mixed stands. Therefore, commercial seed harvesting in mixed stands should be avoided if the production of seed lots of pure coastal or interior Douglas-fir is intended.
► Study on structure, gene flow, and clonality of Euphrates poplar forests in China. ► Even highly fragmented and isolated stands are reproductively connected. ► No genetic differentiation between ...forests close to the river and isolated stands. ► Clonal growth produces contiguous forests, but only if groundwater supply is good. ► Dispersal abilities and groundwater supply important for management/conservation.
To investigate the influence of groundwater and river dynamics on genetic diversity and clonal growth of Populus euphratica forests along the Tarim river system (Xinjiang Prov., China), we genotyped nine old stands in three study areas of various distance to the main river. Using seven microsatellite loci, 850 genotypes were found among 1701 analyzed trees, with 204 of these comprising at least two trees. Population genetic analyses revealed a low degree of genetic differentiation (Dest=0.014, Gst=0.005), and no restriction to gene flow between stands. The forests can therefore be described by the infinite island model of gene flow. Stands in the three study areas differed strongly in clonality: in area I 82% of all trees grew from root suckers, clones averagely comprised 10.5±2.0 trees; figures in area II were 45% and clones of 4.5±1.0 trees, respectively. Area III had the largest trees, but was almost non-clonal (less than 3% of all trees were root suckers). By measuring current ground water depth and reconstructing river courses over more than one century, the varying ground water supply was identified as the most likely reason for the different degree of clonal growth. Neither survival nor lifespan of a stand depends on clonal growth. In the harsh environments inhabited by P. euphratica, the most important function of clonal growth may be the enhanced reproductive impact of large clones.
Genetic diversity is considered to be a prerequisite for adaptation and adaptability as it is a key element of biological diversity. However, the monitoring of genetic diversity has tended to be ...ignored in biodiversity monitoring. We report a comprehensive genetic monitoring effort in two dominant forest tree species, which was started with a baseline survey in 12 European beech populations and 10 Norway spruce populations in Germany. The standardized experimental design is based on collecting samples of at least 250 adult trees, and 400 natural regeneration and 400 seed samples and their genotyping with 15–16 high-resolution SSR markers. In addition to commonly used mean values across the markers to quantify genetic diversity, we placed special emphasis on various marker-based, pedigree-based and demographic models for estimating the contemporary effective population size N
e
of the different generations. In both beech and spruce, no variation in genetic diversity with mean values across markers was detectable between the studied stands and between age cohorts. We detected that stable allelic diversity in progeny generations is ensured by sufficient gene flow from surrounding forests. However, estimates of effective population size show marked differentiation among populations and among age cohorts. Natural regeneration samples appear to converge on the parent generation, while seed samples show a clear bottleneck effect. The N
e
parameter can be used to derive conclusions for sustainable natural regeneration management in forest stands and for seed stand approvals including adequate seed collections for appropriate artificial regenerations.The sibship frequency-based method for N
e
estimates is presented as much more robust than the widely used LD estimates, which often fail for samples with too weak relatedness. Despite the distinct kinship structure in our monitoring plots, the contemporary effective population size proves to be an essential parameter for assessing the integrity of the reproductive system.
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