Harrison Rhett D, Rønsted Nina, Xu Lei, Rasplus Jean-Yves, Cruaud Astrid
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Science, Mengla, Yunnan, China.
PLoS One. 2012;7(6):e38432. doi: 10.1371/journal.pone.0038432. Epub 2012 Jun 5.
Fig trees are a ubiquitous component of tropical rain forests and exhibit an enormous diversity of ecologies. Focusing on Ficus subgenus Sycomorus, a phenotypically diverse and ecologically important Old World lineage, we examined the evolution of fruit traits using a molecular phylogeny constructed using 5 kilobases of DNA sequence data from 63 species (50% of global diversity). In particular, we ask whether patterns of trait correlations are consistent with dispersal agents as the primary selective force shaping morphological diversity or if other ecological factors may provide a better explanation? Fig colour, size and placement (axial, cauliflorous, or geocarpic) were all highly evolutionarily liable, and the same fruit traits have evolved in different biogeographic regions with substantially different dispersal agents. After controlling for phylogenetic autocorrelation, we found that fig colour and size were significantly associated with fig placement and plant-life history traits (maximum plant height and leaf area, respectively). However, contrary to prevailing assumptions, fig placement correlated poorly with known dispersal agents and appears more likely determined by other factors, such as flowering phenology, nutrient economy, and habitat preference. Thus, plant life-history, both directly and through its influence on fig placement, appears to have played a prominent role in determining fruit traits in these figs.
榕树是热带雨林中普遍存在的组成部分，展现出极为多样的生态环境。我们聚焦于无花果亚属Sycomorus，这是一个表型多样且在旧世界具有重要生态意义的谱系，利用从63个物种（占全球多样性的50%）的5千碱基DNA序列数据构建的分子系统发育树，研究了果实性状的进化。具体而言，我们探讨性状相关性模式是否与传播媒介作为塑造形态多样性的主要选择力相一致，或者其他生态因素是否能提供更好的解释？无花果的颜色、大小和着生位置（轴生、茎花或地果）在进化上都高度易变，相同的果实性状在具有截然不同传播媒介的不同生物地理区域都有进化。在控制了系统发育自相关性之后，我们发现无花果的颜色和大小分别与无花果着生位置和植物生活史性状（最大植株高度和叶面积）显著相关。然而，与普遍假设相反，无花果着生位置与已知传播媒介的相关性很差，似乎更可能由其他因素决定，如开花物候、养分经济和栖息地偏好。因此，植物生活史，无论是直接的还是通过其对无花果着生位置的影响，似乎在决定这些无花果的果实性状方面发挥了重要作用。
