Department of Botany, Box 90338, Duke University, Durham, North Carolia 27708; and.
Am J Bot. 1999 Apr;86(4):512-21.
The life cycles of mosses and other bryophytes are unique among land plants in that the haploid gametophyte stage is free-living and the diploid sporophyte stage is ephemeral and completes its development attached to the maternal gametophyte. Despite predictions that populations of haploids might contain low levels of genetic variation, moss populations are characterized by substantial variation at isozyme loci. The extent to which this is indicative of ecologically important life history variation is, however, largely unknown. Gametophyte plants from two populations of the moss Ceratodon purpureus were grown from single-spore isolates in order to assess variation in growth rates, biomass accumulation, and reproductive output. The data were analyzed using a nested analysis of variance, with haploid sib families (gametophytes derived from the same sporophyte) nested within populations. High levels of life history variation were observed within both populations, and the populations differed significantly in both growth and reproductive characteristics. Overall gametophytic sex ratios did not depart significantly from 1:1 within either population, but there was significant variation among families in both populations for progeny sex ratio. Some families produced predominantly male gametophytes, while others yielded predominantly females. Because C. purpureus has a chromosomal mechanism of sex determination, these observations suggest differential (but unpredictable) germination of male and female spores. Life history observations showed that male and female gametophytes are dimorphic in size, maturation rates, and reproductive output.
藓类植物和其他苔藓植物的生命周期在陆地植物中是独一无二的，因为它们的单倍体配子体阶段是自由生活的，而二倍体孢子体阶段是短暂的，并附着在母体配子体上完成发育。尽管有人预测单倍体种群可能含有低水平的遗传变异，但苔藓种群在同工酶基因座上表现出很大的变异。然而，这种变异在多大程度上反映了具有重要生态意义的生活史变异在很大程度上尚不清楚。为了评估生长速率、生物量积累和繁殖产量的变化，从藓类植物 Ceratodon purpureus 的两个种群中分离出单孢子进行培养，以获得配子体植物。数据使用嵌套方差分析进行分析，将单倍体 sib 家族（来自同一孢子体的配子体）嵌套在种群内。在两个种群中都观察到了高水平的生活史变异，而且种群在生长和繁殖特征上也存在显著差异。总体而言，配子体的性别比例在两个种群中都没有显著偏离 1:1，但在两个种群的家族中，后代的性别比例都存在显著差异。一些家族主要产生雄性配子体，而另一些家族则主要产生雌性配子体。由于 C. purpureus 具有染色体性别决定机制，这些观察结果表明雄性和雌性孢子的萌发存在差异（但不可预测）。生活史观察表明，雄性和雌性配子体在大小、成熟速度和繁殖产量上存在二态性。
