Breeding origins of migrating Ryukyu Robins Erithacus komadori inferred from mitochondrial control region sequences

摘要

We estimated the breeding origins of 40 Ryukyu Robins Erithacus komadori captured outside their known breeding range on the Sakishima Islands, the southern part of Okinawa-jima, and Kyushu based on 1226 base pairs of the mtDNA control region sequence.This mtDNA region is known to be an ideal genetic marker for estimating the breeding origin of migrating individuals since four genetically distinct groups of breeding populations have previously been identified: three groups of the northern subspecies(E. komadori komadori; Tokara, Oh-shima, and Tokunoshima groups) and a single group of the southern subspecies (E. komadori namiyei; Okinawa-jima), each of which consists of mostly endemic haplotypes. Among the migrating individuals, Tokara haplotypes dominated (35 individuals). However, three individuals sampled in the Sakishima Islands had an Oh-shima haplotype and two other individuals had Tokuno-shima haplotypes. The migrating individuals from these two populations were not restricted to certain sexor age classes. The populations in Oh-shima and Tokuno-shima were found to be partially migratory and not completely sedentary, with some individuals migrating as far as the Sakishima Islands. Further studies are needed to clarify the relative frequencyof migratory individuals in these populations. Additionally, individuals with Okinawa-jima haplotypes were not found outside its breeding range during the nonbreeding season, suggesting that individuals in this population are strictly sedentary.