Han Kaiping, Lincoln David E
Department of Biological Sciences, University of South Carolina, Columbia, South Carolina, 29208.
Evolution. 1994 Oct;48(5):1550-1563. doi: 10.1111/j.1558-5646.1994.tb02195.x.
Diplacus aurantiacus contains large amounts of a leaf phenolic resin, an important deterrent to a leaf-eating caterpillar, Euphydryas chalcedona. The resin can also retard water loss during drought. Furthermore, the leaf resin content differs among plants and populations. This study investigates the existence of heritable variation (h ) in resin production and tests for a genetic correlation (r ) between carbon allocation to secondary metabolites and growth rate, as well as with three other vegetative traits. Nine dam and 10 sire plants were chosen randomly at a field site and used to generate 78 full-sib families (19 half-sib families) by crossing all males to all females in a factorial design. Heritability was estimated in two ways, and genetic correlations were estimated by three methods. We found: (1) the heritability of resin production estimated by the regression of offspring on sires was significantly greater than zero (hs2=0.32, P<0.01); (2) the maternal variance in resin content was significantly greater than zero (21.3% of total phenotypic variance); (3) significant negative genetic correlation between resin content and growth rate was observed from two of three methods and was consistent with the phenotypic correlation; and (4) the cost of resin could be assessed quantitatively. The genetic cost of 1 mg in resin is equivalent to 25 mg of dry shoot-biomass growth, but the phenotypic cost is only 2.1 mg. This study indicates that carbon allocation to these secondary metabolites may respond to natural selection, and the phenotypic cost of resin production has a genetic basis in D. aurantiacus. This trade-off suggests that once selection occurs, increased phenolic resin production may result in decreased growth, or vice versa.
橙黄双盘花含有大量的叶片酚醛树脂，这是一种对食叶毛虫欧菲德瑞亚·查尔西多纳的重要威慑物。这种树脂还能在干旱期间减缓水分流失。此外，不同植株和种群的叶片树脂含量也有所不同。本研究调查了树脂产量中遗传变异（h）的存在情况，并测试了次生代谢产物碳分配与生长速率以及其他三个营养性状之间的遗传相关性（r）。在一个田间地点随机选择了9株母本植株和10株父本植株，并通过因子设计将所有雄性与所有雌性杂交，以产生78个全同胞家系（19个半同胞家系）。通过两种方法估计遗传力，并通过三种方法估计遗传相关性。我们发现：（1）通过子代对父本的回归估计的树脂产量遗传力显著大于零（hs2 = 0.32，P < 0.01）；（2）树脂含量的母本方差显著大于零（占总表型方差的21.3%）；（3）从三种方法中的两种观察到树脂含量与生长速率之间存在显著的负遗传相关性，且与表型相关性一致；（4）树脂的成本可以定量评估。树脂中1毫克的遗传成本相当于25毫克干茎生物量的生长，但表型成本仅为2.1毫克。本研究表明，向这些次生代谢产物的碳分配可能对自然选择做出反应，并且树脂产生的表型成本在橙黄双盘花中有遗传基础。这种权衡表明，一旦发生选择，酚醛树脂产量的增加可能导致生长减少，反之亦然。
