Mating system in a clonal Douglas fir (Pseudotsuga menziesii (Mirb) Franco) seed orchard. II. Effective pollen dispersal (original) (raw)
Related papers
1997
Reproductive patterns and effective pollen dispersal were investigated in a Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) clonal seed orchard using 11 isozyme loci as genetic markers. Progenies from 94 mother trees were analysed by the mixed-mating and the neighbourhood models and outcrossing rates were estimated as 0.96 and 0.97, respectively. The proportion of offspring resulting from pollination by males located outside the neighbourhood of each mother tree (30 m in radius) was estimated as 0.54, with 43 per cent of matings resulting from outcrossing with nearby males (within neighbourhoods). The effects of distance and direction of individual males from mother trees, pollen fecundity and phenological synchronization were all significant in determining outcross mating patterns within neighbourhoods. Generally, male reproductive success increased with proximity and phenology overlap with mother tree and pollen fecundity. The effect of different factors influencing male reproductive success varied among the three groups of mother trees divided according to the time of female receptivity (early, intermediate and late). Phenology was important in the early and intermediate groups whereas fecundity was important in the intermediate and late phenology groups. Both distance and directionality effects were significant in the early and late classes. The directionality effect could be partially explained by the wind patterns existing during the pollination period. The mean effective number of males mating with each female within neighbourhoods was 10.95 (49.31 per cent of males within neighbourhoods).
Bessega et al_2017_Implications of mating system and pollen dispersal.pdf
Implications of mating system and pollen dispersal indices for management and conservation of the semi-arid species Prosopis flexuosa (Leguminosae), 2017
Recruitment by fencing of semi-arid trees is a common woodland conservation strategy that may have both positive and negative implications. Domestic herbivores can act as efficient dispersal seed agents but they can also affect the survival and growth of the trees first stages. Prosopis flexuosa (algarrobo) woodlands represent the most important plant community in the Monte region in Argentina and as this resource is affected by deforestation, grazing, natural fires and replacement of natural ecosystems by croplands, in order to protect the ‘‘algarrobo” a reserve had been established. As efficient management and conservation program depends on the information on population structure and mating system, the objectives of this work were to estimate mating and pollen dispersal patterns in a wild P. flexuosa population from the Ñacuñan fenced to exclude domestic cattle for 40 years. This population is mainly outcrosser (tm = 0.996), sensitive to inbreeding depression at seed stage, having relative reduced pollen mediated gene dispersal distance (4.56–20.35 m), which favors inbreeding as a consequence of mating between related individuals. Our results suggest that for ex situ conservation the distance that would be enough to avoid full sib sampling among harvested seed-trees is about 20 m. Collecting seeds from different pods reduce the proportion of full sibs within progeny arrays. For in situ conservation it is important to take into account that forest patches separated by more than 250 m are expected to be iso- lated, increasing the risk of genetic variability loss, inbreeding increase and population extinction. The results are discussed in reference to the ‘‘algarrobo” management program; while in some case excluding big mammals from the stands should be advisable, the interaction with long dispersal big herbivores might be considered as a strategy to promote increased outbreeding reducing the rate of mating between related individuals.
Conservation Genetics, 2013
Extensive realized pollen and seed flow across populations reduces inbreeding and spatial genetic structure (SGS) and increases the genetic diversity and effective size within populations. Inbreeding, SGS and realized patterns of pollen and seed dispersal of the dioecious, wind pollinated Araucaria angustifolia were investigated based on microsatellite loci. The study was conducted in a 7.2 ha plot established within a continuous Araucaria Forest in Southern Brazil. In the plot, all 290 adult trees were mapped, measured (diameter at breast height, dbh), sexed, sampled and genotyped. We also sampled, measured (total height), mapped and genotyped 223 juveniles. A total of 86 alleles were detected in the sample (n = 513). Adults and juveniles showed a positive and significant fixation index (minimum of 0.096), suggesting inbreeding or Wahlund effect. Juveniles presented a significant aggregated distribution which was associated with a genetic aggregation (significant SGS up to 20 m), indicating that near neighbor trees may be related due the limited seed dispersal. However, the intensity of SGS was not significantly higher among juveniles (Sp = 0.0041) than adults (Sp = 0.0026). Realized pollen and seed immigration into the plot was low (pollen = 6 %; seeds = 5 %) and the patterns of pollen and seed dispersal were similar. Pollen was dispersed over long distances (343 m), but 50 % was dispersed up to 124 m. Seeds also reached long distances (318 m), with 50 % being dispersed up to 133 m. Our results are discussed in terms of auto-ecology and the genetic conservation of A. angustifolia populations.
Heredity, 2005
Patterns of pollen dispersal were investigated in a small, isolated, relict population of Pinus sylvestris L., consisting of 36 trees. A total-exclusion battery comprising four chloroplast and two nuclear microsatellites (theoretical paternity exclusion probability EP ¼ 0.996) was used to assign paternity to 813 seeds, collected from 34 trees in the stand. Longdistance pollen immigration accounted for 4.3% of observed matings. Self-fertilization rate was very high (0.25), compared with typical values in more widespread populations of the species. The average effective pollen dispersal distance within the stand was 48 m (or 83 m excluding selfs). Half of effective pollen was dispersed within 11 m, and 7% beyond 200 m. A strong correlation was found between the distance to the closest tree and the mean mating-distance calculated for single-tree progenies. The effective pollen dispersal distribution showed a leptokurtic shape, with a large and significant departure from that expected under uniform dispersal. A maximum-likelihood procedure was used to fit an individual pollen dispersal distance probability density function (dispersal kernel). The estimated kernel indicated fairly leptokurtic dispersal (shape parameter b ¼ 0.67), with an average pollen dispersal distance of 135 m, and 50% of pollen dispersed beyond 30 m. A marked directionality pattern of pollen dispersal was found, mainly caused by the uneven distribution of trees, coupled with restricted dispersal and unequal male success. Overall, results show that the number and distribution of potential pollen donors in small populations may strongly influence the patterns of effective pollen dispersal. Heredity (2005) 94, 13-22.
Canadian Journal of Forest Research, 1996
The reproductive success of orchard and nonorchard pollens was studied in seeds from megastrobili exposed during different stages of pollen shedding in a Pinussylvestris L. seed orchard. Wind pollination was controlled experimentally by isolating and then temporarily exposing the megastrobili to four different stages of pollen shedding by orchard trees. The amount of pollen contamination in the seed crop was determined using isozyme markers and an undetected gamete model. The estimated level of pollen contamination was 48% when megastrobili were exposed during the entire pollination season. Contamination was highest (60%) when megastrobili were exposed before actual pollen shedding by orchard trees, and lowest (27%) in seeds from megastrobili exposed during maximum pollen shedding by orchard trees. Reproductive success was measured several ways: as the total number of seeds produced in each treatment, as the ratio or proportion of mature cones per megastrobilus, and as the number of...
Scientific Reports, 2018
Seed orchards main function is delivering breeding programs’ gains in the form of genetically improved seedlings. They are unique experimental populations, perfectly suited for studying various pollination environments (natural or otherwise), affecting their mating system parameters. Here, under different pollination environment (natural and intrusive (pollen augmentation and/or bloom-delay)), the mating system of a second generation, wind-pollinated, coastal Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco) seed orchard was evaluated over four years. Using DNA microsatellite markers and bulk seed samples, we conducted pedigree reconstruction to assign each seed’s male and female parents, followed by determining the extent of pollen contamination (external gene flow), selfing rate, and, parental gametic contribution for each year. Overall, external pollen contamination rates ranged between 10 and 28%, selfing rate varied between 12 and 17%, and 80% of the seed crops ...
Factors Affecting Pollen Dispersal in High-density Apple Orchards
Hortscience, 2001
Knowledge of pollen dispersal is essential for maximizing cross-fertilization in apples (Malus ×domestica Borkh.) and achieving optimal orchard design. Using allozyme markers, we examined dispersal of pollen from trees of a single cultivar ('Idared') throughout two apple orchards. In each orchard, the percentage of seeds sired by 'Idared' was estimated for trees sampled at regular intervals along three transects, extending up to 18 rows (86 m) from the closest donor trees. The percentage of seed sired by 'Idared' pollen ranged from 76% to 1% of seed sampled for a row. No differences in pollen dispersal were found among transects, despite differences in proximity to the bee colonies. Variation in 'Idared' siring success was attributable to the cultivar of the fruit-bearing trees as well as their distance to the nearest 'Idared' tree. Cultivar effects were associated with differences in flowering overlap, but not cross-compatibility with the pollenizer. Furthermore, flowering overlap was a good predictor of siring success only when the flowering times of competing pollenizer cultivars were also considered. The implications for orchard design are discussed.
Short distance pollen movement in a wind-pollinated tree, Quercus lobata (Fagaceae)
Forest Ecology and Management, 2009
Pollen movement has two important aspects that must be taken into account when conserving or managing tree populations at a local or regional scale: the local distribution of genotypes via short distance dispersal (SDD) and genetic connectivity across landscapes via long distance dispersal (LDD) (Sork and Smouse, 2006). Wright (1943, 1946) recognized that local dispersal could lead to population subdivision as an outcome of restricted propagule flow. The neighbourhood size (N e), the effective number of randomly mating individuals in a population within an area defined by the scale of dispersal, is the entity of contemporary evolutionary processes. The size of the local pollen neighbourhood is influenced by the short distance part of the pollen dispersal curve. The shape of the dispersal kernel is critical, because the steeper it is, near the origin, the more near-neighbour matings will dominate the pollen pool. Meanwhile the fatness or thinness of the tail will indicate whether long distance dispersal is common or rare (Austerlitz
Molecular Ecology, 2005
Knowing the extent of gene movements from parents to offspring is essential to understand the potential of a species to adapt rapidly to a changing environment, and to design appropriate conservation strategies. In this study, we develop a nonlinear statistical model to jointly estimate the pollen dispersal kernel and the heterogeneity in fecundity among phenotypically or environmentally defined groups of males. This model uses genotype data from a sample of fruiting plants, a sample of seeds harvested on each of these plants, and all males within a circumscribed area. We apply this model to a scattered, entomophilous woody species, Sorbus torminalis (L.) Crantz, within a natural population covering more than 470 ha. We estimate a high heterogeneity in male fecundity among ecological groups, both due to phenotype (size of the trees and flowering intensity) and landscape factors (stand density within the neighbourhood). We also show that fat-tailed kernels are the most appropriate to depict the important abilities of long-distance pollen dispersal for this species. Finally, our results reveal that the spatial position of a male with respect to females affects as much its mating success as ecological determinants of male fecundity. Our study thus stresses the interest to account for the dispersal kernel when estimating heterogeneity in male fecundity, and reciprocally.