Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancón, Republic of Panama.
Oecologia. 2012 Feb;168(2):519-31. doi: 10.1007/s00442-011-2112-z. Epub 2011 Sep 6.
Two opposing niche processes have been shown to shape the relationship between ecological traits and species distribution patterns: habitat filtering and competitive exclusion. Habitat filtering is expected to select for similar traits among coexisting species that share similar habitat conditions, whereas competitive exclusion is expected to limit the ecological similarity of coexisting species leading to trait differentiation. Here, we explore how functional traits vary among 19 understory palm species that differ in their distribution across a gradient of soil resource availability in lower montane forest in western Panama. We found evidence that habitat filtering influences species distribution patterns and shifts community-wide and intraspecific trait values. Differences in trait values among sites were more strongly related to soil nutrient availability than to variation in light or rainfall. Soil nutrient availability explained a significant amount of variation in site mean trait values for 4 of 15 functional traits. Site mean values of leaf nitrogen and phosphorus increased 37 and 64%, respectively, leaf carbon:nitrogen decreased 38%, and specific leaf area increased 29% with increasing soil nutrient availability. For Geonoma cuneata, the only species occurring at all sites, leaf phosphorus increased 34% and nitrogen:phosphorus decreased 42% with increasing soil nutrients. In addition to among-site variation, most morphological and leaf nutrient traits differed among coexisting species within sites, suggesting these traits may be important for niche differentiation. Hence, a combination of habitat filtering due to turnover in species composition and intraspecific variation along a soil nutrient gradient and site-specific niche differentiation among co-occurring species influences understory palm community structure in this lower montane forest.
生境过滤和竞争排斥。生境过滤预计会在具有相似生境条件的共存物种中选择相似的特征，而竞争排斥预计会限制共存物种的生态相似性，导致特征分化。在这里，我们探讨了在巴拿马西部低山地森林中，19 种不同土壤资源分布的林下棕榈物种的功能特征如何变化。我们发现，生境过滤影响物种分布模式，并改变了整个群落和种内特征值。不同地点的特征值差异与土壤养分供应的关系比光照或降雨量的差异更为密切。土壤养分供应解释了 15 个功能特征中有 4 个的站点平均特征值的显著变化。在所有站点都存在的唯一物种 Geonoma cuneata 中，叶片磷增加了 34%，氮：磷减少了 42%，随着土壤养分的增加，叶片碳：氮减少了 38%，比叶面积增加了 29%。除了站点间的差异外，大多数形态和叶片养分特征在同一站点内共存物种之间也存在差异，这表明这些特征可能对生态位分化很重要。因此，由于物种组成的周转率和土壤养分梯度上的种内变异以及共存物种之间特定地点的生态位分化，生境过滤的结合影响了这个低山地森林中林下棕榈群落的结构。
