Linking plant spatial aggregation with reproductive traits and near-source seed dispersal: ecological adaptation to heavy grazing

植物的生态适应策略一直备受生态学者的关注,然而很少有研究能够整体地、系统地揭示植物适应草食动物的生态过程。本研究以内蒙古荒漠草原建群种短花针茅为研究对象,分析了重度放牧和不放牧处理下短花针茅的繁殖个体性状、种子性状以及土壤种子库和种群空间格局。研究结果表明,生殖个体性状方面,生殖枝数量对营养枝数量有正向影响;土壤种子库方面,短花针茅生殖个体基部的土壤种子库中短花针茅密度显著高于旁边裸地土壤种子库中短花针茅的密度,且与种子性状和裸地土壤种子库显著负相关;在种群空间格局方面,重度放牧下短花针茅种群空间聚集分布。我们的结果认为在重度放牧处理下,生殖活动在短花针茅的资源分配中处于主导地位;短花针茅植物种群通过调控种子形态特征,采用就近扩散的生态策略,促进了幼年种群与成年种群在较小的尺度上空间正关联,从而形成“安全岛”。     

Local population genetic structure of the montane caddisfly Drusus discolor is driven by overland dispersal and spatial scaling

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Sex inequality driven by dispersal

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Tau aggregation is driven by a transition from random coil to beta sheet structure

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Pollen dispersal and gene flow within and into a population of the alpine monocarpic plant Campanula thyrsoides

Background and Aims

Gene flow by seed and pollen largely shapes the genetic structure within and among plant populations. Seed dispersal is often strongly spatially restricted, making gene flow primarily dependent on pollen dispersal within and into populations. To understand distance-dependent pollination success, pollen dispersal and gene flow were studied within and into a population of the alpine monocarpic perennial Campanula thyrsoides.

Methods

A paternity analysis was performed on sampled seed families using microsatellites, genotyping 22 flowering adults and 331 germinated offspring to estimate gene flow, and pollen analogues were used to estimate pollen dispersal. The focal population was situated among 23 genetically differentiated populations on a subalpine mountain plateau (<10 km²) in central Switzerland.

Key Results

Paternity analysis assigned 110 offspring (33·2 %) to a specific pollen donor (i.e. ‘father’) in the focal population. Mean pollination distance was 17·4 m for these offspring, and the pollen dispersal curve based on positive LOD scores of all 331 offspring was strongly decreasing with distance. The paternal contribution from 20–35 offspring (6·0–10·5 %) originated outside the population, probably from nearby populations on the plateau. Multiple potential fathers were assigned to each of 186 offspring (56·2 %). The pollination distance to ‘mother’ plants was negatively affected by the mothers'' degree of spatial isolation in the population. Variability in male mating success was not related to the degree of isolation of father plants.

Conclusions

Pollen dispersal patterns within the C. thyrsoides population are affected by spatial positioning of flowering individuals and pollen dispersal may therefore contribute to the course of evolution of populations of this species. Pollen dispersal into the population was high but apparently not strong enough to prevent the previously described substantial among-population differentiation on the plateau, which may be due to the monocarpic perenniality of this species.