Search

The efficient conversion of tissues into reproductive success is a crucial aspect affecting the evolution of life histories. Masting, the interannually variable and synchronous seed production in perennial plants, is a strategy that can enhance reproductive efficiency by mitigating seed predation and pollen limitation. However, evaluating benefits is insufficient to establish whether efficiency has improved, as such assessments neglect the associated costs of masting, particularly during the critical seed‐to‐seedling stage. We conducted a parentage analysis of seedlings and adults in a population of 209 Sorbus aucuparia trees, monitored over 23 years, providing pioneering documentation of the effects of masting on the fitness of individual trees beyond the seed stage. Our results show high costs of interannual variation that can be mitigated by high synchrony and reveal the existence of phenotypes that appear to reap the benefits of masting while avoiding its costs through regular reproduction. [ABSTRACT FROM AUTHOR]

Seed production is known to reveal high individual variation in tree populations, shaping regeneration and competition patterns. In isolated populations, individual variation in seed production drives genetic drift and inbreeding, increasing the risk of local extinction. In this study, we investigated the variation in seed production within a natural remnant population of a dioecious conifer, Taxus baccata. The observed individual seed counts were highly variable and showed excessive zeros. The observed zeros were well explained by the small trunk circumference and the absence of neighboring males. Non-zero seed counts increased with female trunk circumference, neighboring male circumference, and female heterozygosity. In addition, seed production decreased with elevation, presumably reflecting water availability at the site. We did not observe an effect of canopy closure but, since trunk circumference showed a strong relationship with canopy closure, light availability may indirectly influence seed production by determining resources available for reproduction. Overall, the study shows that seed production in yew is strongly pollen-limited. However, for similarly sized and pollen-supplemented trees, seed production may be further determined by an individual genotype and micro-environmental factors. Whether the observed variation in seed production drives density-dependent effects (e.g. mortality) in recruited seedlings remains a matter for future studies. [ABSTRACT FROM AUTHOR]

Quercus pubescens on its only stand in Poland, in the Bielinek Reserve, was for years treated as atypical, being an effect of hybridizing with co-occurring Q. petraea and Q. robur. In the study, the leaves of these three species and their hybrids in Bielinek were characterized with 20 macro-morphological and eight micro-morphological traits, and statistically compared with Q. pubescens from Italy. Genetic assignments revealed a low number of hybrids. Quercus pubescens leaves from Bielinek and Italy were visually similar, the significant differences between them concerned mainly the size of the leaves. It was accepted that the characteristics of Q. pubescens from Bielinek were within the range of species variability and were similar to the doubtful species Q. virgiliana (Q. pubescens s.l.). Differences between Q. pubescens from Bielinek and Italy could have resulted from the acclimatization to the local conditions, or origination form a different refugium, and long-term isolation. The group of Q. petraea leaves joining morphological features of Q. petraea and Q. pubescens was detected, blurring the morphological differences between species and impeding the recognition of hybrids. This phenomenon is explained by the acclimatization of part of the population to the local micro-climate or by the ancient hybridization. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Assessing the distribution of chloroplast DNA (cpDNA) haplotype variation is useful for studying the phylogeography of angiosperms. In the last two decades the cpDNA phylogeography of white oaks in Europe has been extensively studied, mostly based on the PCR-RFLP technique. However, PCR-RFLPs have low mutation rates and are primarily useful for reconstructing patterns at large geographical scales and lack resolution at fine spatial scales. Here we evaluate the usefulness of chloroplast microsatellites (cpSSR) as an alternative to PCRRFLPs in Polish oak populations which have been underrepresented in previous studies. Eighty-five cpSSR haplotypes were detected using 14 cpSSR loci and a broad collection of 6680 trees sampled throughout Poland. Haplotype diversity was significantly lower in Q. petraea (He = 0.798) than in Q. robur (He = 0.820). Only 17 haplotypes (H01-H17) were found in 13 or more individuals, comprising together 97.9% of the sample. Most frequent cpSSR haplotypes were related to PCR-RFLP haplotypes, establishing the cross-references between the two marker systems. There was significant concordance between the matrices of genetic distances obtained by PCR-RFLP haplotypes and cpSSR haplotypes. Phylogenetic relationships among cpSSR haplotypes supported the existence of the three predominant maternal lineages of oaks in Poland: Iberian (7.8%), Apennine (20.6%) and Balkan (65.5%). The results are discussed with regards to the usefulness of cpSSR markers for phylogeographic studies. [ABSTRACT FROM AUTHOR]

Masting (synchronous and interannually variable seed production) is frequently called a reproductive strategy; yet it is unclear whether the reproductive behaviour of individuals has a heritable component. To address this, we used 22 years of annual fruit production data from 110 Sorbus aucuparia L. trees to examine the contributions of genetic factors to the reproductive phenotype of individuals, while controlling for environmental variation. Trees sharing close genetic relationships and experiencing similar habitat conditions exhibited similar levels of reproductive synchrony. Trees of comparable sizes displayed similar levels of year-to-year variation in fruiting, with relatedness contributing to this variation. External factors, such as shading, influenced the time intervals between years with abundant fruit production. The effects of genetic relatedness on the synchrony of reproduction among trees and on interannual variation provide long-awaited evidence that the masting phenotype is heritable, and can respond to natural selection.