東亞地區台灣吻鰕虎 (Rhinogobius formosanus) 之生活史及族群遺傳

Abstract

Rhinogobius formosanus is an amphidromous species of goby, which had been long considered endemic to northern Taiwan. However, a population was reported from Fujian, China in 2012. Recently, two populations in Taiwan were identified and a landlocked population at the upstream of the Feitsui Reservoir in Taipei was confirmed. Nevertheless, the populations in China were still being understudied and the knowledge of the biogeographic pattern of this species is still limited. There are two objectives in this study. First, to investigate as to whether there is a landlocked population of the R. formosanus in China by analyzing the otolith Sr:Ca ratios. Second, to examine the mechanism that causes the disjunction of R. formosanus in Taiwan and China by comparing the genetic structure among the five populations. In this study, the samples were collected from five locations, two from Fujian, China and three from northern Taiwan, including one landlocked habitat. Mitochondrial DNA was used as the molecular marker to study the population genetics of the five R. formosanus populations, while the otolith Sr:Ca ratios were used to reconstruct the life history of the gobies. The results showed a consistently low Sr:Ca ratios in the gobies from Fuqing in China, suggesting the Fuqing population being a landlocked goby. On the other hand, the gobies from Fuding, China showed a high to low Sr:Ca ratios, suggesting the Fuding population being amphidromous gobies. As for the molecular analysis results, the populations between Taiwan and China showed a significant genetic differentiation based on the AMOVA analysis result. Besides, the two amphidromous populations in Taiwan showed a recent population expansion based on the neutrality test result, but not the China populations and the Bayesian skyline result suggested it happened at the end of glaciation. Although R. formosanus can enter the ocean during the larval stage, it might not travel for a long distance, which can prevent the gene flow between the Taiwan and China populations. The population migration result showed a direction of Taiwan to China, however, the AMOVA and ФST results suggested the vicariance effect stronger than dispersal. The results of population expansion happened in Taiwan’s amphidromous populations might be due to the time scale and environmental differences. In conclusion, a landlocked population is found in China and the disjunction of the China and Taiwan populations is caused by a vicariance in which the Taiwan Strait formed a barrier that separated the populations.