Seed heteromorphism in Crepis sancta (Asteraceae): Performance of two morphs in different environments
Seed heteromorphism in Crepis sancta (Asteraceae): Performance of two morphs in different environments
复制标题
DOI：
10.2307/3546016
复制
发表时间：
1997-06-01
期刊：
影响因子：
3.4
通讯作者：
Lepart, J
中科院分区：
文献类型：
--
作者：
Imbert, E;Escarre, J;Lepart, J
金鱼草是一种一年生复合体，产生异形种子。外围瘦果，根据它们在果穗中的位置命名，较重，没有乳突，而中央瘦果较轻，有乳突。形态分化与胚胎大小的差异有关：来自外围瘦果的胚胎是来自中央瘦果的胚胎的两倍。由于幼苗的大小对生长有影响，我们检验了这样的假设，即外围瘦果和中央瘦果的重量差异导致了对生物和非生物胁迫的抗性的差异。我们研究了在不同的环境条件下，生长在不同营养水平和不同密度的种内和种间竞争条件下，植物从每种种子形态产生的生殖生物量。在没有竞争的情况下，在高营养水平和低营养水平下，两种变种的生殖生物量没有差异。在种内竞争中，来自外围瘦果的植物占优势，来自中央瘦果的植物占主导地位。在种间竞争中，周围瘦果胚胎大小越大，密度越高。在与高相对生长率的一年生种无芒雀麦的竞争中，形态差异比与多年生低相对生长率的无芒雀麦更重要。在与其他一年生物种竞争时，中央瘦果的重量较小是一个劣势。理论认为，每种种子形态必须在生态上不同，才能保持异形性。竞争能力的差异代表了这两种瘦果之间的生态差异之一，因此可能有助于圣叶猴混合策略的成功。
Crepis sancta is an annual composite that produces heteromorphic seeds. Peripheral achenes, named from the position they occupy within the fruiting heads, are heavier and without a pappus whereas central achenes are lighter and have a pappus. The morphological differentiation is associated with a difference in embryos size: embryos from peripheral achenes are twice as heavy as those from central achenes. As seedling size has consequences for growth, we tested the hypothesis that the difference in weight between peripheral and central achenes leads to a differentiation in resistance to biotic and abiotic stress. We studied the reproductive biomass produced by plants from each seed morph, grown under different environmental conditions: al high and low nutrient levels, and at various densities of intraspecific and interspecific competition. In the absence of competition, there was no difference in reproductive biomass between the two morphs at high and low nutrient levels. In intraspecific competition, the plants derived from peripheral achenes dominated those derived from central achenes. In interspecific competition, the greater size of the embryo of peripheral achenes was advantageous at high density. The difference between morphs was more important in-competition with an annual species of high RGR, Bromus madritensis, than with a perennial species of low RGR, Bromus erectus.The low weight of central achenes represents a disadvantage when competing with other annual species. Theory suggests that each seed morph must differ ecologically in order to maintain heteromorphism. The differentiation in competitive ability represents one of the ecological differences between the two types of achenes and may therefore contribute to the success of the mixed strategy in Crepis sancta.