Miyazawa Kae, Lechowicz Martin J
Department of Biology, McGill University, 1205 Avenue Docteur Penfield, Montréal, Québec, Canada H3A 1B1.
Ann Bot. 2004 Oct;94(4):635-44. doi: 10.1093/aob/mch184. Epub 2004 Aug 25.
Allowing for dispersal limitation, a species' geographic distribution should reflect its environmental requirements. Comparisons among closely related species should reveal adaptive differentiation in species characteristics that are consistent with their differences in geographic distribution. This expectation was tested by comparing characteristics of seedlings of spruce species in relation to environmental factors representative of their current natural ranges.
Seedlings were grown from a total of 34 populations representing eight North American spruce (Picea) species in a controlled environment chamber for 140 d. Traits related to the potential of seedling establishment, including tolerance to stress events (high temperature, desiccation) were evaluated. Correlations were sought between these characteristics and modal values of latitude, aridity and continentality in the geographic range of each species.
Many seedling traits changed significantly in response to stress events, but only the response of chlorophyll concentration differed significantly among species. Components of seedling growth were good correlates of species distribution. Seedling relative growth rate (RGR) and specific leaf area (SLA) were positively correlated with latitude, and leaf weight ratio (LWR) negatively correlated with aridity. Seed mass was negatively correlated with latitude.
Relationships found between seedling traits and geographical variation in environmental conditions suggest that factors such as temperature regime, water availability and perhaps litter depth affect species range in North American spruces. Seedling characteristics appear to be elements in a reasonably distinct environmental niche for each spruce species at the continental scale.
考虑到扩散限制，一个物种的地理分布应反映其环境需求。对近缘物种进行比较，应能揭示物种特征中与地理分布差异相一致的适应性分化。通过比较云杉物种幼苗的特征与代表它们当前自然分布范围的环境因素，对这一预期进行了检验。
从代表北美8种云杉（云杉属）的总共34个种群中培育出幼苗，在可控环境箱中培养140天。评估了与幼苗定植潜力相关的性状，包括对胁迫事件（高温、干燥）的耐受性。研究了这些特征与每个物种地理分布范围内纬度、干旱度和大陆性的模态值之间的相关性。
许多幼苗性状对胁迫事件有显著变化，但只有叶绿素浓度的响应在物种间有显著差异。幼苗生长成分与物种分布有良好的相关性。幼苗相对生长率（RGR）和比叶面积（SLA）与纬度呈正相关，叶重比（LWR）与干旱度呈负相关。种子质量与纬度呈负相关。
幼苗性状与环境条件地理变异之间的关系表明，温度状况、水分可利用性以及可能的凋落物深度等因素影响北美云杉的物种分布范围。在大陆尺度上，幼苗特征似乎是每个云杉物种在相当独特的环境生态位中的要素。
