Stone J, Björklund M
Department of Animal Ecology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden.
Proc Biol Sci. 2002 Apr 22;269(1493):861-5. doi: 10.1098/rspb.2001.1934.
Assortative mating characterizes the situation wherein reproducing individuals pair according to similarity. Usually, the impetus for this bias is attributed to some type of mate choice conferring benefits (e.g., increased fitness or genetic compatibility) and, thereby, promoting speciation and phenotypic evolution. We investigate, by computer simulation of an evolving deme-structured snail population, the ramifications ensuing from passive assortative mating wherein couples exhibiting opposite shell coil direction phenotypes experience a physical constraint on mating success: putative mating partners inhabiting stout dextral and sinistral shells are unable to exchange sperm. Because shell coil chirality genotype is encoded at a single locus by shell coil alleles that are inherited maternally, snails containing sinistral alleles can present the typical dextral phenotype. Consequently, the incidence of a sinistral allele in as few as one snail can be manifested as prezygotic reproductive isolation within a deme in a subsequent generation. However, because the efficacy of achieving this type of prezygotic reproductive isolation is affected by shell form, the likelihood and product of single-gene speciation should be determined by deme interaction (migration) and composition (morphological distribution). We test this hypothesis and show how stochastic migration interacts with passive assortative mating yielding morphologically induced prezygotic reproductive isolation to produce new species phenotypes. The results show that demes can achieve rapid macroscopic phenotypic transformation and indicate that sympatric speciation might be more plausible than naturalists recognize conventionally.
选型交配描述了繁殖个体根据相似性配对的情况。通常，这种偏好的推动力归因于某种类型的配偶选择，这种选择能带来益处（例如，提高适应性或基因兼容性），从而促进物种形成和表型进化。我们通过对一个不断进化的具有种群结构的蜗牛种群进行计算机模拟，研究被动选型交配所产生的后果，即表现出相反壳螺旋方向表型的配偶在交配成功方面受到物理限制：居住在粗壮右旋壳和左旋壳中的潜在配偶无法交换精子。由于壳螺旋手性基因型由母系遗传的壳螺旋等位基因在单个位点编码，含有左旋等位基因的蜗牛可以呈现典型的右旋表型。因此，在少数蜗牛中存在的左旋等位基因的发生率，在下一代的种群中可能表现为合子前生殖隔离。然而，由于实现这种合子前生殖隔离的效果受壳形态的影响，单基因物种形成的可能性和产物应由种群间相互作用（迁移）和组成（形态分布）来决定。我们检验了这一假设，并展示了随机迁移如何与被动选型交配相互作用，产生形态诱导的合子前生殖隔离，从而产生新的物种表型。结果表明，种群可以实现快速的宏观表型转变，并表明同域物种形成可能比博物学家传统上所认为的更具合理性。
