Ricklefs Robert E, Renner Susanne S
Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, 19104-6018.
Institute of Systematic Botany, Johannes Gutenberg-University, 55099, Mainz, Germany.
Evolution. 1994 Oct;48(5):1619-1636. doi: 10.1111/j.1558-5646.1994.tb02200.x.
Variation in species and genus richness among families of flowering plants was examined with respect to four classification variables: geographical distribution, growth form, pollination mode, and dispersal mode. Previous studies have estimated rates of species proliferation from age and contemporary diversity. Here we found that the earliest appearances in the fossil record are correlated with contemporary familial species richness, abundance in the fossil record, and the independent variables considered in this analysis. Thus, we believe that the fossil record does not provide reasonable estimates of the ages of families and that the rate of species proliferation cannot be calculated from such data without bias. Accordingly, our subsequent analyses were based on contemporary species richness of families. Although the classification variables were interrelated, each made largely independent contributions to familial species richness. Cosmopolitan families were 5.6 times more species-rich than strictly tropical families and 35 times more species-rich than strictly temperate families. Families including both herbaceous and woody growth forms were 5.7 and 14 times more species-rich than families with either growth form alone. Although animal pollination was significantly associated with elevated familial species richness, the effect was statistically weak. The most prominent effect was that families with both abiotic and biotic dispersal had more than 10 times as many species as families with either dispersal mode alone. Our analyses also revealed that families having both dispersal modes were more likely to have several growth forms, suggesting that evolutionary flexibility of morphology may be generalized over diverse aspects of life history. These results do not support the idea that pollination and dispersal by animals were primarily responsible for the tremendous proliferation of angiosperm species, either by producing population structures conducive to speciation or by applying selection for diversification. Instead, the importance of varied dispersal mode, growth form, and climate zone in predicting high familial species richness suggests that a capacity to diversify morphologically and physiologically may have been primarily responsible for high rates of species proliferation in the flowering plants.
我们针对四个分类变量，研究了开花植物科属间物种丰富度的差异，这四个变量分别是地理分布、生长形式、授粉方式和传播方式。此前的研究已根据年代和当代多样性估算了物种增殖率。在此我们发现，化石记录中的最早出现情况与当代科的物种丰富度、化石记录中的丰度以及本分析中考虑的自变量相关。因此，我们认为化石记录无法为科的年代提供合理估算，并且无法无偏差地从此类数据中计算物种增殖率。相应地，我们后续的分析基于科的当代物种丰富度。尽管分类变量相互关联，但每个变量对科的物种丰富度都做出了很大程度上独立的贡献。世界性分布的科的物种丰富度比严格热带分布的科高5.6倍，比严格温带分布的科高35倍。包含草本和木本生长形式的科的物种丰富度分别比仅有一种生长形式的科高5.7倍和14倍。尽管动物授粉与科的物种丰富度升高显著相关，但这种影响在统计学上较弱。最显著的影响是，具有非生物和生物传播方式的科的物种数量是仅有一种传播方式的科的10倍以上。我们的分析还表明，具有两种传播方式的科更有可能具有多种生长形式，这表明形态学的进化灵活性可能在生活史的多个方面普遍存在。这些结果并不支持以下观点：动物授粉和传播要么通过产生有利于物种形成的种群结构，要么通过施加多样化选择，从而主要促成了被子植物物种的大量增殖。相反，多样的传播方式、生长形式和气候带在预测高科的物种丰富度方面的重要性表明，在形态学和生理学上实现多样化的能力可能是开花植物物种高增殖率的主要原因。
