Experimental analysis of ecological and genetic effects upon native rare species by the invasion of exotic related species

采用生态学、行为学和群体遗传学的方法，以韩国罗得鱼（Rhode us ocellatus kurumeus）和罗得鱼（r.o. ocellatus Roo）为研究对象，分析了外来近缘种入侵导致本土物种灭绝的机理。在水族馆（6对Rok和3对Roo）中检测交配行为和繁殖成功率，在人工池塘（50对Rok和5对Roo）中监测基因型和基因频率的变化。此外，通过计算机模拟，从理论上推断了袋鼠入侵导致袋鼠灭绝的条件。在水族中，雄鱼的交配行为和雌鱼的繁殖能力均优于雄鱼。亚种间交配成功率较低，尤以Roo（♂）与Rok（♀）的交配成功率较低。交配频率以韩国最高，亚种间次之。而Roo（♀）与Rok（♂）杂交的幼虫基因型最高。在池塘中，杂交品种的幼虫基因型最高，而韩国品种的幼虫基因型最低，这是自第二年实验以来未观察到的。杂交品种在第三年增加到96%，在所有检测的位点中，杂交品种Roo的基因频率约为70%。综上所述，袋鼠入侵导致袋鼠灭绝的因素在个体和基因之间存在差异。韩国个体的灭绝是由交配行为、繁殖能力、胚胎发育中的杂种优势、缺乏前交和后交隔离造成的，而基因的灭绝是由基因适合度的差异造成的。在不同初始条件下对上述因素进行了计算机模拟，验证了这一建议的有效性。

Mechanism of native species extinction by the invasion of exotic related species was analyzed by ecological and ethological methods, together with that of population genetics, under the rearing experiments of Rhode us ocellatus kurumeus (Rok) and R. o. ocellatus (Roo). Mating behavior and reproductive success were examined in aquaria (6 pairs of Rok and 3 pairs of Roo), and changes in genotype and gene frequencies were monitored in an artificial pond (50 pairs of Rok and 5 pairs of Roo). In addition, the condition of Rok extinction caused by the invasion of Roo was theoretically inferred by using computer simulation.In aquaria, Roo was superior to Rok in mating behavior of males and reproductivity of females. Mating success was lower between subspecies, especially between Roo (♂) X Rok (♀). Mating frequency was the highest in Rok, and the next between subspecies. However, genotype of larvae was the highest in hybrids between Roo ( ♀) X Rok (♂). In pond, genotype of larvae was the highest in hybrids, while it was the lowest in Rok, which has not been observed since the next year of experiments. Hybrids increased to 96% in the third year, and gene frequency of Roo in hybrids amounted to about 70% in all the loci examined.In conclusion, it was suggested that the factors causing the extinction of Rok by the invasion of Roo are different between individuals and genes. The extinction of Rok individuals is caused by mating behavior, reproductivity, heterosis in embryogenesis, and lacks of premating and postmating isolations, while that of genes is caused by the difference in gene fitness. The validity of this suggestion was confirmed by the computer simulation that incorporated the above-mentioned factors under the various initial conditions.