Hybridization among foundation tree species influences the structure of associated understory plant communities
Hybridization among foundation tree species influences the structure of associated understory plant communities
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基础树种之间的杂交影响相关林下植物群落的结构
作者：
L. J. Lamit;T. Wojtowicz;Z. Kovács;S. Wooley;Matthew S. Zinkgraf;T. Whitham;R. Lindroth;C. Gehring
了解遗传同一性如何影响群落结构是进化生态学的主要焦点，但很少有研究在此背景下研究相同营养水平的生物体之间的相互作用。在一个普通的花园里，有来自一个杂交系统的树木（白杨）。以杨树（Populus angustifolia James）为研究材料，验证了林下植物群落结构受遗传差异影响的假设，并探讨了叶面凝聚单宁（CTs）和光合有效辐射（PAR）的作用机制。一些研究结果支持了我们的假设：(1)林下生物量和盖度沿遗传梯度从鹅毛叶松到鹅毛叶松增加。（ii）在相同的杂交梯度上，物种丰富度降低，物种组成发生变化。(3)胡杨叶片CT浓度和PAR浓度从针叶林降低到白杨。（iv）林下物种丰富度随叶面面积的增加而增加；然而，生物量、盖度和组成与CTs没有关系，并且没有层下变量与PAR相关。(v)结构方程模型表明，叶面CTs是联系林下树遗传与林下丰富度的主要机制。本研究利用一个以自然定植的外来物种为主的实验系统，证明了树木杂交产生的遗传梯度可以影响林下植物。
Understanding how genetic identity influences community structure is a major focus in evolutionary ecology, yet few studies examine interactions among organisms in the same trophic level within this context. In a common garden containing trees from a hybrid system (Populus fremontii S. Wats. Populus angustifolia James), we tested the hypothesis that the structure of establishing understory plant communities is influenced by genetic differences among trees and ex- plored foliar condensed tannins (CTs) and photosynthetically active radiation (PAR) as mechanisms. Several findings sup- port our hypothesis: (i) Understory biomass and cover increase along the genetic gradient from P. angustifolia to P. fremontii .( ii) Along the same hybridization gradient, species richness decreases and species composition shifts. (iii) Populus foliar CT concentrations and PAR decrease from P. angustifolia to P. fremontii .( iv) Understory species rich- ness increases with foliar CTs; however, biomass, cover, and composition show no relationship with CTs, and no under- story variables correlate with PAR. (v) Structural equation modeling suggests that foliar CTs are a primary mechanism linking overstory tree genetics with understory richness. Using an experimental system dominated by naturally colonizing exotic species, this study demonstrates that a genetic gradient created by tree hybridization can influence understory plants.