Scale dependence of reproductive failure in fragmented Echinacea populations.
Scale dependence of reproductive failure in fragmented Echinacea populations.
复制标题
破碎的紫锥菊种群繁殖失败的规模依赖性。
作者：
S. Wagenius
我在一个为期三年的研究中调查了生长在支离破碎的草原景观中的紫锥菊的繁殖情况。我量化了本地丰富的开花同种在个人为基础的空间尺度和人口为基础的空间尺度。回归分析表明，花粉限制增加，而结实率和繁殖力下降，与隔离的个别植物。隔离，定义为距离k（第）最近的开花同种，是一个很好的预测花粉限制，考虑所有最近的邻居（k = 1-33），但强度的关系，量化的R2，在中间尺度（k = 2-18）达到峰值。在中等尺度（k = 3-4），隔离结实率和繁殖力的关系同样最强。个体密度对繁殖影响的尺度依赖性（x米内开花植物的密度）类似于隔离。在人口规模的分析表明，花粉限制下降显着人口规模。结实率和繁殖力也随着种群规模的增加而下降，但只有在1998年才有显著的下降。无论是量化本地丰富的人口或个人为基础的措施，由于花粉限制生殖失败是一个一致的后果紫锥菊稀缺。然而，以个人为基础的措施，当地丰富的预测花粉限制从更广泛的植物样本，一个简单的模型比人口规模。具体而言，最大的网站，自然保护区，是由植物与中间的个人隔离，并预测，中间花粉限制，但其庞大的人口规模预测人口平均花粉限制。
I investigated reproduction in a three-year study of Echinacea angustifolia, purple coneflower, growing in a fragmented prairie landscape. I quantified the local abundance of flowering conspecifics at individual-based spatial scales and at a population-based spatial scale. Regression analyses revealed that pollen limitation increased while seed set and fecundity decreased with isolation of individual plants. Isolation, defined as the distance to the k(th) nearest flowering conspecific, was a good predictor of pollen limitation, for all nearest neighbors considered (k = 1-33), but the strength of the relationship, as quantified by R2, peaked at intermediate scales (k = 2-18). The relationship of isolation to seed set and fecundity was similarly strongest at intermediate scales (k = 3-4). The scale dependence of individual density effects on reproduction (density of flowering plants within x meters) resembled that of isolation. Analyses at a population-based scale showed that pollen limitation declined significantly with population size. Seed set and fecundity also declined with population size, but significantly so only in 1998. Whether quantifying local abundance with population- or individual-based measures, reproductive failure due to pollen limitation is a consistent consequence of Echinacea scarcity. However, individual-based measures of local abundance predicted pollen limitation from a wider sample of plants with a simpler model than did population size. Specifically, the largest site, a nature preserve, is composed of plants with intermediate individual isolation and, as predicted, intermediate pollen limitation, but its large population size poorly predicted population mean pollen limitation.