Ecology of hemiepiphytism in fig species is based on evolutionary correlation of hydraulics and carbon economy
Ecology of hemiepiphytism in fig species is based on evolutionary correlation of hydraulics and carbon economy
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DOI：
10.1890/11-0269.1
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发表时间：
2011-11-01
期刊：
影响因子：
4.8
通讯作者：
Cao, Kun-Fang
中科院分区：
文献类型：
--
作者：
Hao, Guang-You;Goldstein, Guillermo;Cao, Kun-Fang
木本半附生树种（Hs）是热带雨林的重要组成部分，在水分关系和碳经济方面与非半附生树种（NHs）有着显著的差异，但在进化背景下对两种生长形式的生理生态特征进行比较的研究较少。使用常见的花园植物属榕树，功能性状相关的植物水力学和碳经济进行了比较，为7个NH和7个HS在其成年陆地“树一样”的生长阶段。我们使用非遗传独立的对比来检验这一假设，即水的可用性差异选择对比套的性状在Hs和NHs，驱动功能性状，包括水力传导率和光合特性之间的进化相关性。两种生长形式的物种在功能性状上存在差异; Hs具有显著较低的木质部导水率和气孔导度，以及较高的瞬时光合水分利用效率。叶形态和结构性状也显着不同的两种生长形式之间。HS有显着较小的叶片，较高的叶质量单位面积（LMA），和较小的木质部导管腔直径。在所有的物种中，导水率与叶片气体交换呈正相关，表明高度的水力光合协调。更重要的是，这些相关性的支持实施系统发育独立对比的相关性，这表明大多数性状的相关性出现通过反复趋同进化，而不是作为一个结果的机会事件在深节点的血统。木质部导水率的变化也集中与一套其他功能性状相关的碳经济和增长，如LMA，水分利用效率，叶片养分浓度，光合养分利用效率，表明重要的生理限制或功能性状之间的权衡。这一特征群的变化显然与适应干旱倾向的冠层生长在早期的生命周期的Hs和明显影响的生态生理学的后期陆地阶段，这些物种。水力学和相关性状的进化灵活性可能是热带雨林中榕属物种高度多样化的基础之一。
Woody hemiepiphytic species (Hs) are important components of tropical rain forests, and they have been hypothesized to differ from non-hemiepiphytic tree species (NHs) in adaptations relating to water relations and carbon economy; but few studies have been conducted comparing ecophysiological traits between the two growth forms especially in an evolutionary context. Using common-garden plants of the genus Ficus, functional traits related to plant hydraulics and carbon economy were compared for seven NHs and seven Hs in their adult terrestrial "tree-like'' growth phase. We used phylogenetically independent contrasts to test the hypothesis that differences in water availability selected for contrasting suites of traits in Hs and NHs, driving evolutionary correlations among functional traits including hydraulic conductivity and photosynthetic traits. Species of the two growth forms differed in functional traits; Hs had substantially lower xylem hydraulic conductivity and stomatal conductance, and higher instantaneous photosynthetic water use efficiency. Leaf morphological and structural traits also differed strikingly between the two growth forms. The Hs had significantly smaller leaves, higher leaf mass per area (LMA), and smaller xylem vessel lumen diameters. Across all the species, hydraulic conductivity was positively correlated with leaf gas exchange indicating high degrees of hydraulic-photosynthetic coordination. More importantly, these correlations were supported by correlations implemented on phylogenetic independent contrasts, suggesting that most trait correlations arose through repeated convergent evolution rather than as a result of chance events in the deep nodes of the lineage. Variation in xylem hydraulic conductivity was also centrally associated with a suite of other functional traits related to carbon economy and growth, such as LMA, water use efficiency, leaf nutrient concentration, and photosynthetic nutrient use efficiency, indicating important physiological constraints or trade-offs among functional traits. Shifts in this trait cluster apparently related to the adaptation to drought-prone canopy growth during the early life cycle of Hs and clearly affected ecophysiology of the later terrestrial stage of these species. Evolutionary flexibility in hydraulics and associated traits might be one basis for the hyper-diversification of Ficus species in tropical rain forests.