Population Genetic Structure among Intra-Annual Arrival Waves of the Japanese Eel Anguilla japonica in Northern Taiwan

Population genetic structure among intraannual
arrival waves of the Japanese eel Anguilla japonica in northern Taiwan. Zoological Studies 46(5): 583-
590. A previous study showed that the Japanese eel Anguilla japonica Temminck and Schlegel is not a panmictic
species, as it is divided into low- and high-latitude groups, but it shows no significant genetic differentiation
among year cohorts in the same habitat. However, based on hatching dates back-calculated from otolith of
elvers recruited in Taiwan in the winter, the arrival waves of elvers are from different intra-annual cohorts with
separate spawning times. To test if temporal genetic differentiation exists within intra-annual cohorts, 7 polymorphic
microsatellite DNA loci were examined. Four arrival waves of Japanese eel elvers were collected from
a single location in northern Taiwan from Nov. 2000 to Mar. 2001. Deviations from Hardy-Weinberg equilibrium
were found in three of the 7 loci after the Bonferroni correction, and five of the 7 loci were used for a genetic
variation test. No significant genetic differentiation was observed among the overall sample (FST = 0.0029, p =
0.173), and subtle, but significant, differentiation was only found between temporal cohorts of Nov. and Dec.
2000 (FST = 0.0111, p = 0.008). The phylogenetic tree indicates patchiness among elver waves with samples of
Nov. 2000 significantly separated from the others. The assignment test, however, showed a high mixing rate
among each cohorts. These results indicate that arrival waves of elvers in consecutive months at the same
habitat exhibit subtle genetic patchiness but overall lack significant temporal genetic variations.