Genetic Introgression by the Rose Bitterling, Rhodeus ocellatus
ocellatus, into the Japanese Rose Bitterling, R.o.kurumeus
(Teleostei: Cyprinidae)
Kouichi Kawamura , TakayoShi Ueda ,
Ryoichi Arai , Yoshikazu Nagata Kenji Saitoh , Hiroyuki Ohtaka and Yoshihiko
Kanoh
(2001 ) ZOOLOGICAL SCIENCE 18: 1027-1039
Abstract
The Japanese rose bitterling, Rhodeus ocellatus
kurumeus, is an endangered cyprinid species. The main reason of drastic
diminution of R. o. kurumeus has been suggested to be due to
hybridization between this subspecies and R. o. ocellatus introduced from
China. Both RFLP analysis of mitochondrial DNA and RAPD-PCR analysis of genomic
DNA were performed to elucidate the genetic introgression of R. o.
ocellatus into R. o. kurumeus. The two subspecies were distinguished
in the D-loop region of mtDNA by six restriction endonucleases. Rhodeus o.
kurumeus had eleven subspecies-specific RAPD markers and R. o.
ocellatus had two. Except some R. o. kurumeus populations, most of
the populations of R. ocellatus in Japan were hybrids, equipped with
subspecies-specific RAPD markers for the two subspecies, respectively. The
genetic constitution of these markers in hybrids, however, greatly differed
among populations. The R. o. ocellatus mtDNA was predominantly observed
in hybrid populations, except two populations with mtDNAS of the two subspecies.
Judging from the genetic dominance of morphological and physiological characters
of R. o. ocellatus against R. o. kurumeus, hybrids probably have
the same ecological dominance as R. o. ocellatus against R. o.
kurumeus. Therefore, it is considered that R. o. kurumeus not only
has its genetic propertyspoiled by hybridization with R. o. ocellatus,
but also is expelled by R. o. ocellatus and hybrids. The replacement of
mtDNA and genomes of R. o. kurumeus with those of R. o. ocellatus
in hybridization might be accelerated by the backcross between hybrids and R.
o. ocellatus.