DeWalt Saara J, Denslow Julie S, Hamrick J L
Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
Oecologia. 2004 Mar;138(4):521-31. doi: 10.1007/s00442-003-1462-6. Epub 2003 Dec 19.
We tested the hypothesis that the tropical shrub Clidemia hirta appears more shade tolerant and is more abundant in its introduced than native range because of genetic differences in resource acquisition, allocation, and phenotypic plasticity between native and introduced genotypes. We examined growth, biomass allocation, and photosynthetic parameters of C. hirta grown in a greenhouse from seed collected from four populations in part of its native range (Costa Rica) and four populations in part of its introduced range (Hawaiian Islands). Six-month-old seedlings were placed in high (10.3-13.9 mol m(-2) day(-1)) or low (1.4-4.5 mol m(-2) day(-1)) light treatments and grown for an additional 6 months. Our study provided little evidence that Hawaiian genotypes of C. hirta differed genetically from Costa Rican genotypes in ways that would contribute to differences in habitat distribution or abundance. Some of the genetic differences that were apparent, such as greater allocation to stems and leaf area relative to whole plant biomass in Costa Rican genotypes and greater allocation to roots in Hawaiian genotypes, were contrary to predictions that genotypes from the introduced range would allocate more biomass to growth and less to storage than those from the native range. Hawaiian and Costa Rican genotypes displayed no significant differences in relative growth rates, maximal photosynthetic rates, or specific leaf areas in either light treatment. In the high light environment, however, Hawaiian genotypes allocated more biomass to reproductive parts than Costa Rican genotypes. Phenotypic plasticity for only 1 of 12 morphological and photosynthetic variables was greater for Hawaiian than Costa Rican genotypes. We conclude that genetic shifts in resource use, resource allocation, or plasticity do not contribute to differences in habitat distribution and abundance between the native and introduced ranges of C. hirta.
热带灌木希氏姬苗（Clidemia hirta）在引入地比原生地显得更耐荫且更为常见，这是由于原生基因型和引入基因型在资源获取、分配及表型可塑性方面存在基因差异。我们研究了从希氏姬苗原生地（哥斯达黎加）部分地区的四个种群以及引入地（夏威夷群岛）部分地区的四个种群采集的种子在温室中培育的希氏姬苗的生长、生物量分配和光合参数。将六个月大的幼苗置于高光（10.3 - 13.9摩尔·米⁻²·天⁻¹）或低光（1.4 - 4.5摩尔·米⁻²·天⁻¹）处理下，并再生长6个月。我们的研究几乎没有证据表明希氏姬苗的夏威夷基因型在基因上与哥斯达黎加基因型存在差异，而这种差异会导致栖息地分布或丰富度的不同。一些明显的基因差异，比如哥斯达黎加基因型相对于整株生物量对茎和叶面积的分配更多，而夏威夷基因型对根的分配更多，这与引入地基因型会比原生地基因型将更多生物量分配到生长而非储存的预测相反。在两种光照处理下，夏威夷和哥斯达黎加基因型在相对生长速率、最大光合速率或比叶面积方面均无显著差异。然而，在高光环境中，夏威夷基因型比哥斯达黎加基因型将更多生物量分配到生殖部分。在12个形态和光合变量中，只有1个变量的表型可塑性在夏威夷基因型中比在哥斯达黎加基因型中更大。我们得出结论，资源利用、资源分配或可塑性方面的基因变化并不会导致希氏姬苗原生地和引入地在栖息地分布和丰富度上的差异。
