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50 results for “pollen dispersal”

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Data from: Fire-induced population reduction and landscape opening increases gene flow via pollen dispersal in Pinus halepensis

Population reduction and disturbances may alter dispersal, mating patterns and gene flow. Rather than taking the common approach of comparing different populations or sites, here we studied gene flow via wind-mediated effective pollen dispersal on the same plant individuals before and after a fire-induced population drop, in a natural stand of Pinus halepensis. The fire killed 96% of the pine trees in the stand and cleared the vegetation in the area. Thirteen trees survived in two groups separated by ~80 m, and seven of these trees had serotinous (closed) pre-fire cones that did not open despite the fire. We analyzed pollen from closed pre- and post-fire cones using microsatellites. The two groups of surviving trees were highly genetically differentiated, and the pollen they produced also showed strong among-group differentiation and very high kinship both before and after the fire, indicating limited and very local pollen dispersal. The pollen not produced by the survivors also showed significant pre-fire spatial genetic structure and high kinship, indicating mainly within-population origin and limited gene flow from outside, but became spatially homogeneous with random kinship after the fire. We suggest that post-fire gene flow via wind-mediated pollen dispersal increased by two putative mechanisms: 1) a drastic reduction in local pollen production due to population thinning, effectively increasing pollen immigration; 2) an increase in wind speeds in the vegetation-free post-fire landscape. This research shows that dispersal can alleviate negative genetic effects of population size reduction, and that disturbances might enhance gene flow, rather than reduce it.

opencc-zeroDec 2012View details →

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Data from: Pollen dispersal in fragmented populations of the dioecious wind-pollinated tree, Allocasuarina verticillata (drooping sheoak, drooping she-oak; Allocasuarinaceae)

Vegetation clearing, land modification and agricultural intensification have impacted on many ecological communities around the world. Understanding how species respond to fragmentation and the scales over which functionality is retained, can be critical for managing biodiversity in agricultural landscapes. Allocasuarina verticillata (drooping sheoak, drooping she-oak) is a dioecious, wind-pollinated and -dispersed species with key conservation values across southeastern Australia. But vegetation clearing associated with agricultural expansion has reduced the abundance and spatial distribution of this species in many regions. Spatial genetic structure, relatedness among trees, pollen dispersal and mating patterns were examined in fragmented A. verticillata populations selected to represent the types of remnants that now characterise this species. Short scale spatial genetic structure (5–25 m) and relatedness among trees were observed in most populations. Unexpectedly, the two male trees closest to each female did not have a reproductive advantage accounting for only 4–15% of the seed produced in larger populations. Biparental inbreeding was also generally low (<4%) with limited evidence of seed crop domination by some male trees. More male trees contributed to seed crops in linear remnants (mean 17) compared to those from patch remnants (mean 11.3) which may reflect differences in pollen dispersal within the two remnant types. On average, pollen travels ~100 m irrespective of remnant type but was also detected to have dispersed as far as 1 km in open landscapes. Low biparental inbreeding, limited reproductive assurance for near-neighbour and probably related males and variability in the distances over which females sample pollen pools suggest that some mechanism to prevent matings between relatives exists in this species.

opencc-zeroDec 2014View details →

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Data from: Limited pollen dispersal, small genetic neighborhoods, and biparental inbreeding in Vallisneria americana Michx. (Hydrocharitaceae)

Premise of the study: Pollen dispersal is a key process that influences ecological and evolutionary dynamics of plant populations by facilitating sexual reproduction and gene flow. Habitat loss and fragmentation have the potential to reduce pollen dispersal within and among habitat patches. We assessed aquatic pollen dispersal and mating system characteristics in Vallisneria americana -- a water-pollinated plant with a distribution that has been reduced from historic levels. Methods: We examined pollen neighborhood size, biparental inbreeding, and pollen dispersal, based on seed paternity using the indirect paternity method KinDist, from samples of 18 - 39 mothers and 14 - 20 progeny per mother from 3 sites across 2 years. Key Results: On average, fruits contained seeds sired by 7 fathers. We found significant biparental inbreeding and limited pollen dispersal distances (0.8 - 4.34 m). However, in a number of cases correlated paternity did not decline with distance and dispersal could not be reliably estimated. Conclusions: Frequent pollen dispersal is not expected among patches, and even within patches gene flow via pollen will be limited. Limited pollen dispersal establishes genetic neighborhoods which, unless overcome by seed and propagule dispersal, will lead to genetic differentiation even in a continuous population. Unless loss and fragmentation drive populations to extreme sex bias, local pollen dispersal is likely to be unaffected by habitat loss and fragmentation per se because the spatial scale of patch isolation already exceeds pollen dispersal distances. Therefore, managing specifically for pollen connectivity is only relevant over very short distances.

opencc-zeroDec 2017View details →

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Data from: Population density and size influence pollen dispersal pattern and mating system of the predominantly outcrossed Banksia nivea (Proteaceae) in a threatened ecological community

Gene flow is a critical component of plant mating systems and influences population fitness, yet pollen dispersal can be highly variable and influenced by natural and anthropogenic fragmentation. Gene flow through pollen dispersal was investigated in two populations of contrasting size and habitat context in Banksia nivea ssp. uliginosa, a rare species in the Busselton ironstone threatened ecological community with a naturally fragmented distribution. Paternity analysis was conducted with seven microsatellite loci to determine mating system parameters and patterns of pollen dispersal. Outcrossing was high in both populations with a similar level of selfing for both populations despite differences in population size, density and vegetation matrix. Most mating occurred within 10 m of a mother plant in the small, clumped population, while more dispersed mating, up to 50 m from a mother plant, was recorded in the large, less dense population. Our results show that population density and size are important influences on mating system parameters and level of pollen dispersal.

opencc-zeroDec 2017View details →

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Data from: Short distance pollen dispersal and low genetic diversity in a subcanopy tropical rainforest tree, Fontainea picrosperma (Euphorbiaceae)

Gene flow via pollen movement affects genetic variation in plant populations and is an important consideration in plant domestication. Fontainea picrosperma is a subcanopy rainforest tree that is of commercial interest because it is the source of tigilanol tiglate, a natural product used for the treatment of solid tumors. We identify patterns of pollen-mediated gene flow within natural populations of F. picrosperma and estimate genetic parameters and genetic structure between adult and juvenile groups using microsatellite markers. Our results show pollination events occur over much shorter distances than reported for tropical canopy species. At least 63 % of seeds are sired by male trees located within 30 m of the mother. On average, 27 % of the local male population contributed to successful reproduction of F. picrosperma with most fathers siring a single seed, however, the contributions to reproduction were uneven. Larger male trees with more flowers had gre ater reproductive success than those with less flowers (P < 0.05). There were comparatively low levels of genetic variation across the species (HE = 0.405 for adult trees and 0.379 for juveniles) and we found no loss of genetic diversity between adult and juvenile trees. Short distance pollen flow and low genetic diversity is theoretically a prelude to genetic impoverishment, however F. picrosperma has persisted through multiple significant climatic oscillations. Nevertheless, the remaining low genetic diversity is of concern for domestication programs which require maximal genetic diversity to facilitate efficient selective breeding and genetic improvement of this commercially significant species.

opencc-zeroDec 2018View details →

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