Patterns of Effective Pollen Dispersal in Larch: Linking Levels of Background Pollination with Pollen Dispersal Kernels

Abstract

Monitoring patterns of mating and pollen dispersal in forest tree populations subjected to nature conservation is essential to understanding the dynamics of their reproductive processes and might be helpful in making management decisions aimed at conserving genetic diversity and integrity over the long term. However, little is known about effective pollen dispersal in natural populations of conifers, particularly in subdominant species such as larch. We investigated patterns of pollen dispersal in the Polish larch population ofŚwiętokrzyski National Park. The studied population was located on Chełmowa Mountain in a forest complex 160 ha in size, which is relatively isolated from other forest stands. We assessed if local pollen dispersal inferred from pollen dispersal kernels could provide indications of the level of background pollination from sources located outside of the forest complex. The analysis focused on two plots, each encompassing 126 adult trees, and seed samples (n = 600) collected from 20 trees. Using 11 nuclear microsatellites and spatially explicit mating models, we identified details of mating patterns. The rate of self-fertilization was low (0.0268). Background pollination was moderate (0.4058), and the mean pollen dispersal was found to be 167 m and 111 m, based on exponential-power and Weibull dispersal kernels, respectively. Specific simulations performed based on the estimated pollen dispersal kernels provided background pollination levels comparable to those observed for real data, suggesting that the pollen contributing to background pollination likely originated from the studied forest complex and not from other surrounding populations. These results confirm the high potential for maintaining the genetic integrity of the larch population and support efforts aimed at promoting regeneration of the stands, either natural or through the artificial planting of seedlings derived from trees growing in the core larch population of the protected area.

Patterns of Fine-Scale Spatial Genetic Structure and Pollen Dispersal in Giant Sequoia (Sequoiadendron giganteum)

“…Thus, a more extensive sampling of mother trees, or a detailed parentage analysis, is likely needed to determine the existence of gene-flow across these populations. Empirical studies consistently suggest that "fat-tailed" pollen dispersal curves are typical for many wind-dispersed tree species [16,17,19,[46][47][48]77]. Although we found evidence of the leptokurtic dispersal of kernels for giant sequoia pollen, its capacity for LDD may be more limited than many conifers with which it shares a habitat, which have more buoyant pollen.…”

“…Our results indicate that the majority of pollination in giant sequoia occurs over short distances <253 m, which is typical for many tree species, including Pinus pinaster, Quercus lobata, Nothofagus nervosa, and Larix decidua [16,46,48,64]. Moreover, gene dispersal (a measure of the effective pollen and seed average) also appeared to occur over short distances <370 m. Assuming an isolation-by-distance model, Crawford [65] showed that the dispersal parameter (σ 2 e ) is comprised of a seed and pollen dispersal component given by…”

“…For both KinDist and TwoGener, we applied the two parameter (a and b) exponential power distribution to fit the pollen distribution curve, as recommended by Austerlitz et al [45]. This distribution allows for the leptokurtic pattern of pollen dispersal that is commonly observed in wind-pollinated trees [16,17,[45][46][47][48]. We estimated the scale (a) and shape (b) parameters of the dispersal kernel and calculated mean pollen dispersal distances (d) according to Austerlitz et al [45].…”

Pedigree Reconstruction and Spatial Analysis for Genetic Testing and Selection In A Larix Kaempferi (Lamb.) Carrière Plantation

“…De cit of heterozygosity has been detected in Larix sibirica and Larix gmelinii, and attributed to inbreeding [38]. Furthermore, in a study on the larch mating system, the distance of pollen dispersal was reported to be relatively short [32,39,40], and the genetic structure of European larch over its entire distribution was more obvious than those of other conifers [41].…”

Measuring recent effective gene flow among large populations in Pinus sylvestris: Local pollen shedding does not preclude substantial long-distance pollen immigration

“…In particular, the potential for gene exchange among wind-pollinated conifer populations is high, as they are well known for long-distance pollen transport over hundreds of kilometers [1]. However, direct evidences of effective long-distance pollen transport resulting in actual gene flow events are still scarce [7][8][9]. Although observed background pollination from unknown sources into isolated stands is likely to be the result of long distance dispersal events (e.g.…”