Data from: Testing for ecological limitation of diversification: a case study using parasitic plants

Imbalances in phylogenetic diversity could be the result of variable unbounded diversification rates, differing limits on diversity, or a combination of the two. We propose an approach to distinguish between rates and limits as the primary cause of phylogenetic imbalance, using parasitic plants as a model. With sister-taxon comparisons, we show that parasitic plant lineages are typically much less diverse than their autotrophic sisters. We then use age estimates for taxa used in the sister-taxon comparisons to test for correlations between clade age and diversity. We find that parasitic plant diversity is not significantly correlated with the age of the lineage, whereas there is a strong positive correlation between the age and diversity of autotrophic sister lineages. The Ericaceae sister-pair Monotropoideae (parasitic) and Arbutoideae (autotrophic) are sufficiently well samples at the species level to allow more parametric comparisons of diversification patterns. Model-fitting for this group supports ecological limitation in Monotropoideae and unconstrained diversification in Arbutoideae. Thus, differences in diversity between parasitic plants and their autotrophic sisters might be caused by a mixture of ecological limitation and unbounded diversification. A combination of sister-taxon comparisons of diversity and age, coupled with model-fitting of well-sampled phylogenies of focal taxa, provides a powerful test of likely causes of asymmetry in the diversity of lineages.

系统发育多样性（phylogenetic diversity）失衡可能源于可变的无界多样化速率、差异化的多样性限制，或是二者共同作用。本研究以寄生植物为模式类群，提出一种可区分系统发育多样性失衡核心成因——多样化速率与多样性限制——的分析方法。通过姐妹类群（sister-taxon）比较分析，本研究发现寄生植物支系的多样性通常远低于其自养型姐妹类群。随后，本研究利用姐妹类群比较分析中所涉类群的分化时间估算值，检验演化支（clade）分化时间与多样性之间的相关性。结果显示，寄生植物的多样性与支系分化时间并无显著相关性，而自养型姐妹支系的多样性则与分化时间呈现显著正相关。杜鹃花科（Ericaceae）下的一对姐妹支系——寄生型的水晶兰亚科（Monotropoideae）与自养型的草莓树亚科（Arbutoideae）——在物种水平上采样充分，可开展更为精细的多样化模式参数化比较分析。针对该类群的模型拟合结果表明，水晶兰亚科的多样化受生态限制，而草莓树亚科则呈现无约束的多样化模式。由此可见，寄生植物与其自养型姐妹类群之间的多样性差异，可能是生态限制与无界多样化共同作用的结果。将多样性与分化时间的姐妹类群比较分析，与目标类群充分采样的系统发育树（phylogeny）模型拟合相结合，可为支系多样性不对称性的潜在成因提供强有力的检验手段。