[Show abstract][Hide abstract] ABSTRACT: The clam Corbicula leana exists in two forms, hermaphrodites and males. Our previous study on mitochondrial DNA suggested that the male nuclear DNA might have derived from hermaphrodite C. leana relatively recently. To clarify the origin of males in the clam, sequences of the nuclear 28S rDNA divergent domain (which is 441-444 bp long) in androgenetic hermaphrodites and males and dioecious (bisexual) species were analyzed. Unexpectedly, the nuclear 28S rDNA haplotypes of males and hermaphrodites were distinct. Haplotype network analysis indicated that males and hermaphrodites are reproductively isolated from each other without sharing the same nuclear haplotype. These results support a hypothesis that the egg nuclear genome of androgenetic hermaphrodites is replaced by the male sperm genome, and only males develop after fertilization by a male spermatozoon.
Development Genes and Evolution 04/2012; 222(3):181-7. · 1.70 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Rhodeus atremius is an endemic bitterling fish from Japan comprising two endangered subspecies, R. a. atremius and R. a. suigensis. The latter subspecies, which had dramatically declined in last decades, was reported to contain two distinct mtDNA lineages.
In order to estimate the optimized units for conservation management, the genetic structure of R. atremius was inferred by analyzing mtDNA and microsatellite markers (MS). Allelic richness and heterozygosity of MS in R. a. suigensis was less than half that in R. a. atremius. In R. a. suigensis, not only within-population genetic diversity but also among-population genetic divergence was low, with the exception of
population Ah1, while the diversity was high and the divergence showed isolation by distance in R. a. atremius. In mtDNA and MS, R. a. suigensis concordantly formed a single lineage, while R. a. atremius encompassed four mtDNA lineages, two of which were completely admixed into one group on the basis of MS. In population Ah1
a striking introgression between the two subspecies was suggested by a Bayesian-based assignment test, with the presence of
mtDNA haplotype of R. a. atremius. Contrary to the prevailing theory, R. a. suigensis corresponds to a single conservation unit, while three units seem appropriate for R. a. atremius. In addition, low genetic diversity of R. a. suigensis might have arisen mainly as a result of recent bottlenecks before population fragmentation, followed by current anthropogenic
effects. Genetic introgression in population Ah1 was probably the result of human transplantation of R. a. atremius.
KeywordsBottleneck–Evolutionary Conservation Unit–Genetic diversity–Introgression–Metapopulation–
[Show abstract][Hide abstract] ABSTRACT: The appearances and populations of freshwater fish species and the revetment conditions in the creeks were investigated at 48 sampling sites around Sea of Ariake in northwestern Kyushu Island, Japan. Each creek in this survey was classified into three following types by revetment conditions; Type-1: Creeks have earthen revetments except for the crossing to the roads; Type-2: Although there are the concrete revetments in creeks, these revetments are short in height, and the agricultural water crosses over the revetments and reaches bank vegetations or earthen banks except for agricultural off-season; Type-3: There are high concrete revetments in creeks, and the agricultural water do not cross over the revetments in all season. The appearance rates of Hemigrammocypris rasborella was affected by the revetment conditions, and the rates in Type-3 was significantly lower than those in Type-2 and Type-3. The populations of H. rasborella, Rhodeus ocellatus kurumeus, and Pseudorasbora parva was affected by the revetment conditions. In case of H. rasborella and R. ocellatus kurumeus, the populations in Type-3 were significantly lower than those in Type-2 and Type-3. In case of P. parva, the population in Type-3 was significantly lower than in Type-1. These results indicate that the changes of the revetment conditions in the creeks by the farm land consolidation have much impact on the appearances and populations of several freshwater fish species however, the concrete revetments such as Type-2 have low impacts on these species.
[Show abstract][Hide abstract] ABSTRACT: The distributions of seven bitterling species and subspecies—Tanakia lanceolata, T. limbata, Acheilognathus tabira nakamurae, A. rhombeus, Rhodeus ocellatus kurumeus, R. ocellatus ocellatus, and R. atremius atremius—in northern Kyushu were predicted using generalized linear models (GLMs) in order to provide information helpful for conserving native bitterlings and preventing the expansion of alien bitterling species. Predictions were made according to the following procedure: (1) a set of GLMs for each species was formulated using environmental data from 710 sites that were derived using digital maps and GIS software, from which the best fit model for each species was selected using the Akaike information criterion for predicting the fish occurrence, (2) model performance was evaluated based on the receiver-operating characteristics (ROC) analysis using occurrence and environmental data from 362 sites, and (3) potential distributions of the bitterling were analyzed using the best fit models and environmental data for 1,272 sites, of which 200 data points without occurrence data were prepared. The best fit models revealed that 4–6 environmental factors were important in predicting seven bitterling distributions, which was supported by the area under the ROC curve (AUC) values of these fishes ranging from 0.753 to 0.927. The AUC values in model evaluation were significantly greater than 0.5 for six fishes, suggesting the moderate accuracies of these best fit models for predicting the fish distributions. These predictive models can be used for evaluating potential native bitterling richness and the potential distribution expansion of an alien subspecies.
Ichthyological Research 59(2). · 0.90 Impact Factor