Yamauchi Atsushi, Kamite Yukiko
Center for Ecological Research, Kyoto University, Kamitanakami Hirano, Otsu 520-2113, Japan.
J Theor Biol. 2003 Apr 7;221(3):411-24. doi: 10.1006/jtbi.2003.3195.
The evolution of a facultative sexual strategy that simultaneously produced sexual and asexual individuals was studied theoretically, under negative frequency-dependence of fitness. The organism was considered to be diploid, characterized by two loci concerning fitness and determining sexual strategy, between which a certain degree of linkage existed. The locus concerning fitness was assumed to involve two alleles, resulting in three genotypes, the relative fitness of an individual being defined by a decreasing function of frequency of its own genotype on this locus in the population. The sexual reproductive strategy was considered to be determined by three alleles; asexual, obligate sexual and facultative sexual. Simulations under various linkages between loci and level of frequency dependence of fitness showed that a facultative sexual strategy was generally able to invade and increase in the population. In particular, when the level of frequency dependence was high to some degree, the facultative strain producing many sexual individuals tended to exclusively occupy the population. Namely, the frequency-dependent selection resulted in a predominance of obligate sexual strategy over asexual strategy, simultaneously causing a subordination of the former to the facultative sexual strategy. This indicated that the evolution of sex should be considered carefully with respect to the possibility of invasion of facultative sex.
在适合度负频率依赖的情况下，从理论上研究了一种同时产生有性和无性个体的兼性有性策略的进化。该生物体被认为是二倍体，其特征在于与适合度有关并决定有性策略的两个基因座，这两个基因座之间存在一定程度的连锁。假定与适合度有关的基因座涉及两个等位基因，从而产生三种基因型，个体的相对适合度由其自身基因型在种群中频率的递减函数定义。有性生殖策略被认为由三个等位基因决定；无性、专性有性和兼性有性。在基因座之间的各种连锁和适合度频率依赖水平下的模拟表明，兼性有性策略通常能够在种群中入侵并增加。特别是，当频率依赖水平在某种程度上较高时，产生许多有性个体的兼性菌株往往会独占种群。也就是说，频率依赖选择导致专性有性策略相对于无性策略占优势，同时导致前者从属于兼性有性策略。这表明，关于兼性有性入侵的可能性，应该仔细考虑性别的进化。
