1. Where conspecific seedlings occur at high densities, density‐dependent processes tend to depress their performance and survival relative to co‐occurring heterospecifics. We extend this observation to within‐species genetic diversity and relatedness. We posit that seedling growth and survival increase where there is higher genetic diversity, and lower relatedness, among seedling populations, under the expectation that increased genetic dissimilarity among conspecific seedlings affords greater resistance to pathogens.
2. We used estimates of individual seedling genetic diversity (multilocus heterozygosity (sMLH)) and genetic relatedness among conspecific seedlings (pairwise kinship coefficients (LRI)), under high and low conspecific seedling density, coupled with censuses of seedling growth and mortality over 30 months to explore the role of genetic diversity and relatedness on growth and mortality of 1,485 seedlings of four dipterocarp species in an undisturbed Bornean tropical rainforest. We hypothesized that more genetically diverse and less related co‐occurring seedlings would display higher survival and growth rates.
3. In three of our four species, lower genetic diversity increased the probability of mortality over 30 months. We observed no effect of genetic diversity on relative growth rates. Contrary to our expectations, only one species showed a negative effect of increased relatedness on mortality. In two of the four species studied, seedlings that were more genetically related to neighbouring conspecific seedlings in the sample plot were less likely to die, but grew more slowly.
4. Synthesis. Our results confirm that genetic diversity and relatedness among seedlings shape survival probabilities differentially across species. In contrast, we found no differences in mortality and growth rates between plots with low and high seedling density. Our results suggest that a greater abundance of pollen donors could contribute to cohort seedling survival in some species, though not all, and the specific mechanisms by which genetic relatedness determines seedling demography remain uncertain. These results have conservation and management implications in view of changing patterns of gene flow in fragmented, exploited and degraded tropical rainforests, which might differentially influence natural regeneration among species.

中文翻译：

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探索遗传多样性和相关性在树木幼苗生长和死亡中的作用：婆罗洲雨林中的多物种研究

1. 当同种苗以高密度发生时，与共同存在的异种相比，依赖密度的过程往往会降低其性能和存活率。我们将此观察扩展到种内遗传多样性和相关性。我们认为，在期望种群间种间遗传差异增加对病原体具有更大抗性的预期下，幼苗种群之间的遗传多样性较高且相关性较低的地方，幼苗的生长和存活率会提高。
2. 在高和低同种苗密度的情况下，我们使用了个体幼苗遗传多样性（多基因杂合度（sMLH））和同种苗之间的遗传相关性（成对亲缘系数（LRI））的估计值，以及对30个月至30个月内幼苗生长和死亡率的普查。探索遗传多样性和相关性对未受干扰的婆罗洲热带雨林中4个双果皮树种1485株幼苗的生长和死亡的作用。我们假设遗传多样性更高且相关性较低的同时发生幼苗将显示出更高的存活率和生长速率。
3. 在我们四个物种中的三个中，较低的遗传多样性增加了30个月内死亡的可能性。我们没有观察到遗传多样性对相对增长率的影响。与我们的预期相反，只有一种物种显示出相关性增加对死亡率的负面影响。在所研究的四个物种中的两个物种中，与样地中相邻的同种幼苗在遗传上更相关的幼苗死亡的可能性较小，但生长较慢。
4. 综合。我们的结果证实，幼苗之间的遗传多样性和相关性在物种间影响生存概率。相比之下，我们发现在低密度和高密度下，小块土地的死亡率和生长率没有差异。我们的研究结果表明，虽然不是全部，但更大数量的花粉供体可以促进队列幼苗的存活，尽管遗传相关性决定幼苗人口的具体机制仍不确定。鉴于零散的，开发的和退化的热带雨林中基因流模式的变化，这些结果具有保护和管理意义，这可能会不同地影响物种之间的自然再生。