This study investigates a simple model of stage-structured population with density-dependent birth rate. We assume that the breeding season of a population occurs at a certain time of the year, its individuals undergo two stages during their life cycle, and the adjacent generations are nonoverlapping. Reproductive isolation between generations is caused by mature individual death after breeding and leads to the fact that increasing intraspecific competition results in subcritical period-doubling bifurcation in the proposed model. Periodic, quasiperiodic, and chaotic oscillations appear in the model, as well as shifting of the dynamic regime due to multistability. Furthermore, we propose that the maximum possible fecundity of individuals changes during natural evolution and is an adaptive trait controlled by a single diallelic autosomal locus with allelomorphs A and a. As a result, the population consists of three genotypes, namely, аа, АА, and Аа, with different values of reproductive potential. This study shows that the genetic composition of a population (i.e., whether the population will be polymorphic or monomorphic) is mainly determined by the values of the reproductive potentials of heterozygotes and homozygotes. The average reproductive potential of mature individuals and the intensity of self-regulation processes determine the population dynamic mode. The evolutionary development of a population can occur in three ways depending on the current genetic composition at the same values of demographic parameters. The first way gives a monomorphic population with genotype aa. The second one leads to genotype AA monomorphism. And the last way results in polymorphism which presents 2-cycle of genotype's frequencies. The microevolution scenarios of the population's genetic composition found in the proposed model are associated with fluctuations in numbers and are consistent with studies on Pacific pink salmon populations which demonstrate population size fluctuations and genetic differentiation of subpopulations of adjacent generations.

这项研究调查了密度依赖的出生率的阶段结构人口的简单模型。我们假设一个种群的繁殖季节发生在一年的某个时间，其个体在其生命周期中经历两个阶段，并且相邻世代是不重叠的。世代之间的生殖隔离是由繁殖后成熟的个体死亡引起的，并导致以下事实：种内竞争的加剧导致拟议模型中亚临界时期的分叉增加。模型中会出现周期性，准周期和混沌振荡，以及由于多重稳定性而导致的动态状态偏移。此外，一个和一个。结果，种群由三种基因型组成，即аа，АА和Аа，具有不同的生殖潜力。这项研究表明，种群的遗传组成（即种群将是多态性还是单态性）主要取决于杂合子和纯合子的繁殖潜能值。成熟个体的平均生殖潜力和自我调节过程的强度决定了种群动态模式。人口的进化发展可以通过三种方式发生，这取决于当前的人口构成在相同人口统计学参数值下的遗传组成。第一种方法给出基因型为aa的单态种群。第二个导致基因型AA单态性。最后一种方法导致多态性，呈现基因型频率的2个周期。在提出的模型中发现的种群遗传组成的微进化场景与数量波动有关，并且与对太平洋粉红鲑鱼种群的研究一致，该研究表明种群规模波动和相邻世代亚群的遗传分化。