Inouye D W, Taylor O R
Department of Zoology, University of Maryland, 20742, College Park, MD, USA.
Department of Systematics and Ecology, University of Kansas, 66045, Lawrence, Kansas, USA.
Oecologia. 1980 Jan;47(2):171-174. doi: 10.1007/BF00346816.
The perennial monocarp Frasera speciosa (Gentianaceae) flowers at a wide range of sizes and ages with consequent variation in generation time (T), net replacement rate (R ) and intrinsic rate of increase (r). Values of r were calculated for hypothetical cohorts composed of individuals flowering at the same age. Maximum rates of r are achieved by plants which flower at the earliest possible age. Although older plants produce more flowers, this increase is not sufficient to compensate for the effect of increased T on r. Few plants in each population flower at the youngest possible age, and for the majority reproduction is delayed, generation times are longer and r lower than achieved by plants flowering at younger ages. Delayed reproduction may be favored by greater seed set, due to pollinator attraction to larger flower stalks, as well as broader seed dispersal which could increase the probability of seedling establishment. Delays greater than those observed may be selected against by decreasing probability of survival, a decrease in the rate of addition of flowers with increasing size, and slower transitions between leaf number classes in larger plants. Staggered reproduction by an individual's offspring, whether environmentally or genetically determined, has the effect of insuring survival in an environment with high variability in pollinator effectiveness (see d set), germination, and seedling establishment.
多年生单次结果植物美丽花菱草（龙胆科）在大小和年龄差异很大的情况下开花，导致世代时间（T）、净增殖率（R）和内禀增长率（r）有所不同。r值是针对由在相同年龄开花的个体组成的假设队列计算得出的。最早开花的植物实现了r的最大速率。尽管 older plants produce more flowers，但这种增加不足以弥补T增加对r的影响。每个种群中很少有植物在可能的最年轻年龄开花，对于大多数植物来说，繁殖会延迟，世代时间更长，r值低于较年轻开花植物所达到的水平。延迟繁殖可能因传粉者被更大的花茎吸引而导致结实率更高，以及种子传播范围更广而有利于种子萌发，从而增加幼苗建立的概率。大于观察到的延迟可能会因生存概率降低、随着植株大小增加花朵增加速率降低以及较大植株叶数等级之间的转变较慢而被淘汰。个体后代的交错繁殖，无论是由环境还是基因决定的，都具有确保在传粉有效性（见结实率）、萌发和幼苗建立高度可变的环境中生存的作用。
