LeRoy Carri J, Whitham Thomas G, Keim Paul, Marks Jane C
Department of Biological Sciences, Northern Arizona University, Flagstaff 86011, USA.
Ecology. 2006 Jan;87(1):255-61. doi: 10.1890/05-0159.
Although it is understood that the composition of riparian trees can affect stream function through leaf litter fall, the potential effects of genetic variation within species are less understood. Using a naturally hybridizing cottonwood system, we examined the hypothesis that genetic differences among two parental species (Populus fremontii and P. angustifolia) and two groups of their hybrids (F1 and backcrosses to P. angustifolia) would affect litter decomposition rates and the composition of the aquatic invertebrate community that colonizes leaves. Three major findings emerged: (1) parental and hybrid types differ in litter quality, (2) decomposition differs between two groups, a fast group (P. fremontii and F1 hybrid), and a slow group (P. angustifolia and backcross hybrids), and (3) aquatic invertebrate communities colonizing P. fremontii litter differed significantly in composition from all other cross types, even though P. fremontii and the F1 hybrid decomposed at similar rates. These findings are in agreement with terrestrial arthropod studies in the same cottonwood system. However, the effects are less pronounced aquatically than those observed in the adjacent terrestrial community, which supports a genetic diffusion hypothesis. Importantly, these findings argue that genetic interactions link terrestrial and aquatic communities and may have significant evolutionary and conservation implications.
虽然人们知道河岸树木的组成可以通过落叶影响溪流功能，但物种内遗传变异的潜在影响却鲜为人知。利用一个自然杂交的三角叶杨系统，我们检验了这样一个假设：两个亲本物种（弗里蒙特杨和狭叶杨）及其两组杂种（F1代和回交至狭叶杨的后代）之间的遗传差异会影响落叶分解速率以及在叶片上定殖的水生无脊椎动物群落的组成。出现了三个主要发现：（1）亲本类型和杂种类型在落叶质量上存在差异，（2）两组之间的分解情况不同，一组分解速度快（弗里蒙特杨和F1代杂种），另一组分解速度慢（狭叶杨和回交杂种），（3）定殖在弗里蒙特杨落叶上的水生无脊椎动物群落的组成与所有其他杂交类型有显著差异，尽管弗里蒙特杨和F1代杂种的分解速度相似。这些发现与在同一三角叶杨系统中进行的陆地节肢动物研究结果一致。然而，这些影响在水生环境中不如在相邻陆地群落中观察到的那么明显，这支持了遗传扩散假说。重要的是，这些发现表明遗传相互作用将陆地和水生群落联系起来，可能具有重大的进化和保护意义。
