Fischer D G, Hart S C, Whitham T G, Martinsen G D, Keim P
School of Forestry, Northern Arizona University, Bldg. 82, Box 15018, Flagstaff, AZ 86011-5018, USA.
Oecologia. 2004 Apr;139(2):288-97. doi: 10.1007/s00442-004-1505-7. Epub 2004 Feb 6.
Genetic variation in dominant species can affect plant and ecosystem functions in natural systems through multiple pathways. Our study focuses on how genetic variation in a dominant riparian tree ( Populus fremontii, P. angustifolia and their natural F(1) and backcross hybrids) affects whole-tree water use, and its potential ecosystem implications. Three major patterns were found. First, in a 12-year-old common garden with trees of known genetic makeup, hybrids had elevated daily integrated leaf-specific transpiration ( E(tl); P=0.013) and average canopy conductance ( G(c); P=0.037), with both E(tl) and G(c) approximately 30% higher in hybrid cross types than parental types. Second, delta(13)C values of leaves from these same trees were significantly more negative in hybrids ( P=0.004), and backcross hybrids had significantly more negative values than all other F(1) hybrid and parental types ( P<0.001). Third, in the wild, a similar pattern was found in leaf delta(13)C values where both hybrid cross types had the lowest values ( P<0.001) and backcross hybrids had lower delta(13)C values than any other tree type ( P<0.001). Our findings have two important implications: (1). the existence of a consistent genetic difference in whole-tree physiology suggests that whole-tree gas and water exchange could be another pathway through which genes could affect ecosystems; and (2). such studies are important because they seek to quantify the genetic variation that exists in basic physiological processes-such knowledge could ultimately place ecosystem studies within a genetic framework.
优势物种的遗传变异可通过多种途径影响自然系统中的植物和生态系统功能。我们的研究聚焦于一种优势河岸树（弗里蒙特杨、窄叶杨及其天然F1代和回交杂种）的遗传变异如何影响整棵树的水分利用及其潜在的生态系统影响。发现了三种主要模式。第一，在一个有已知基因组成树木的12年生共同园地里，杂种具有更高的日综合叶特定蒸腾速率（E(tl)；P = 0.013）和平均冠层导度（G(c)；P = 0.037），杂种交叉类型的E(tl)和G(c)均比亲本类型高约30%。第二，这些相同树木叶片的δ(13)C值在杂种中显著更负（P = 0.004），回交杂种的值比所有其他F1杂种和亲本类型显著更负（P < 0.001）。第三，在野外，叶片δ(13)C值也发现了类似模式，杂种交叉类型的值最低（P < 0.001），回交杂种的δ(13)C值比任何其他树型都低（P < 0.001）。我们的发现有两个重要意义：（1）。整棵树生理学中存在一致的遗传差异表明，整棵树的气体和水分交换可能是基因影响生态系统的另一条途径；（2）。此类研究很重要，因为它们试图量化基本生理过程中存在的遗传变异——此类知识最终可将生态系统研究置于遗传框架内。
