Department of Entomology, University of Wisconsin-Madison, 1630 Linden Dr., Madison, WI, USA.
Forest Entomology, Swiss Federal Research Institute for Forest, Snow, and Landscape Research WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland.
Ann Bot. 2023 Feb 7;131(1):229-242. doi: 10.1093/aob/mcac071.
At the population level, genetic diversity is a key determinant of a tree species' capacity to cope with stress. However, little is known about the relative importance of the different components of genetic diversity for tree stress responses. We compared how two sources of genetic diversity, genotype and cytotype (i.e. differences in ploidy levels), influence growth, phytochemical and physiological traits of Populus tremuloides in the presence and absence of environmental stress.
In a series of field studies, we first assessed variation in traits across diploid and triploid aspen genotypes from Utah and Wisconsin under non-stressed conditions. In two follow-up experiments, we exposed diploid and triploid aspen genotypes from Wisconsin to individual and interactive drought stress and defoliation treatments and quantified trait variations under stress.
We found that (1) tree growth and associated traits did not differ significantly between ploidy levels under non-stressed conditions. Instead, variation in tree growth and most other traits was driven by genotypic and population differences. (2) Genotypic differences were critical for explaining variation of most functional traits and their responses to stress. (3) Ploidy level played a subtle role in shaping traits and trait stress responses, as its influence was typically obscured by genotypic differences. (4) As an exception to the third conclusion, we showed that triploid trees expressed 17 % higher foliar defence (tremulacin) levels, 11 % higher photosynthesis levels and 23 % higher rubisco activity under well-watered conditions. Moreover, triploid trees displayed greater drought resilience than diploids as they produced 35 % more new tissue than diploids when recovering from drought stress.
Although ploidy level can strongly influence the ecology of tree species, those effects may be relatively small in contrast to the effects of genotypic variation in highly diverse species.
在种群水平上，遗传多样性是树种应对胁迫能力的关键决定因素。然而，人们对遗传多样性的不同组成部分对树木胁迫反应的相对重要性知之甚少。我们比较了两种遗传多样性来源，即基因型和细胞型（即倍性水平的差异），在存在和不存在环境胁迫的情况下，如何影响颤杨的生长、植物化学和生理特性。
在一系列野外研究中，我们首先评估了来自犹他州和威斯康星州的二倍体和三倍体白杨基因型在非胁迫条件下的性状变异性。在两项后续实验中，我们将来自威斯康星州的二倍体和三倍体白杨基因型暴露于单独和交互的干旱胁迫和去叶处理下，并在胁迫下量化性状变化。
我们发现：（1）在非胁迫条件下，倍性水平对树木生长和相关性状没有显著差异。相反，树木生长和大多数其他性状的变异是由基因型和种群差异驱动的。（2）基因型差异对于解释大多数功能性状及其对胁迫的反应的变异性至关重要。（3）倍性水平在塑造性状及其胁迫反应方面起着微妙的作用，因为其影响通常被基因型差异所掩盖。（4）作为第三个结论的例外，我们表明三倍体树木在水分充足的条件下表现出 17%更高的叶片防御（震颤素）水平、11%更高的光合作用水平和 23%更高的 Rubisco 活性。此外，三倍体树木比二倍体树木表现出更强的耐旱性，因为它们在从干旱胁迫中恢复时比二倍体树木产生 35%更多的新组织。
尽管倍性水平可以强烈影响树种的生态学，但与高度多样化物种的基因型变异的影响相比，这些影响可能相对较小。
