BackgroundCarassius auratus is a primary freshwater fish with bisexual diploid and unisexual gynogenetic triploid lineages. It is distributed widely in Eurasia and is especially common in East Asia. Although several genetic studies have been conducted on C. auratus, they have not provided clear phylogenetic and evolutionary descriptions of this fish, probably due to selection bias in sampling sites and the DNA regions analysed. As the first step in clarifying the evolutionary entity of the world's Carassius fishes, we attempted to clarify the phylogeny of C. auratus populations distributed in East Asia.ResultsWe conducted a detailed analysis of a large dataset of mitochondrial gene sequences [CR, 323 bp, 672 sequences (528 sequenced + 144 downloaded); CR + ND4 + ND5 + cyt b, 4669 bp in total, 53 sequences] obtained from C. auratus in East Asia. Our phylogeographic analysis revealed two superlineages, one distributed mainly among the Japanese main islands and the other in various regions in and around the Eurasian continent, including the Ryukyus and Taiwan. The two superlineages include seven lineages with high regional specificity that are composed of endemic populations indigenous to each region. The divergence time of the seven lineages was estimated to be 0.2 million years ago (Mya) by a fossil-based method and 1.0-1.9 Mya by the molecular clock method. The antiquity and endemism of these lineages suggest that they are native to their respective regions, although some seem to have been affected by the artificial introduction of C. auratus belonging to other lineages. Triploids of C. auratus did not form a monophyletic lineage but were clustered mostly with sympatric diploids.ConclusionsThe results of the present study revealed the existence of two superlineages of C. auratus in East Asia that include seven lineages endemic to each of the seven regions examined. The lack of substantial genetic separation between triploids and diploids indicates that triploids are not composed of a single independent lineage. The ancient origins and evolutionary uniqueness of the seven lineages warrant their conservation. An overall phylogenetic framework obtained from the present study will be of use for estimating the phylogenetic relationships of Carassius fishes on the Eurasian continent.

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Abstract.-Largemouth bass Micropterus salmoides and smallmouth bass M. dolomieu have been introduced into freshwater habitats in Japan, with potentially serious consequences for native fish populations. In this paper we apply the technique of ecological niche modeling using the genetic algorithm for rule-set prediction (GARP) to predict the potential distributions of these two species in Japan. This algorithm constructs a niche model based on point occurrence records and ecological coverages. The model can be visualized in geographic space, yielding a prediction of potential geographic range. The model can then be tested by determining how well independent point occurrence data are predicted according to the criteria of sensitivity and specificity provided by receiver-operator curve analysis. We ground-truthed GARP's ability to forecast the geographic occurrence of each species in its native range. The predictions were statistically significant for both species (P Ͻ 0.001). We projected the niche models onto the Japanese landscape to visualize the potential geographic ranges of both species in Japan. We tested these predictions using known occurrences from introduced populations of largemouth bass, both in the aggregate and by habitat type. All analyses robustly predicted known Japanese occurrences (P Ͻ 0.001). The number of smallmouth bass in Japan was too small for statistical tests, but the 10 known occurrences were predicted by the majority of models.Assessing the threat of species invasions and the possible spread of such species is a global challenge that requires a global perspective (Carlton * Corresponding author: ewiley@ku.edu.1 Order of authorship is alphabetical, reflecting the collaborative nature of this paper.2 Present address: Biodiversity Research Center, University of Kansas, Lawrence, Kansas 66045, USA.3 Present address: Department of Life Science, Faculty of Bioresources, Mie University, 1515 Kamihama, Tsu, Mie 514-8507, Japan. Received October 9, 2003; accepted December 3, 2003 1996; Enserink 1999). To achieve this perspective, we can apply analytical tools and use information on ecological landscapes that can be gathered on a global scale as well as specimen records to seek the sets of factors that are useful in forecasting places where the establishment of species is possible. The point is not necessarily to learn more about the ecology of the species-this would require detailed study of local landscapes. Rather, the aim is to build models of the ecological niche requirements of a particular species within its native range with respect to factors that are available globally, to test whether these models can predict

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Sequence analysis on the mitochondrial DNA control region was conducted for seven samples of amphidromous ayu Plecoglossus altivelis, six from the Japanese Archipelago and one from the Korean Peninsula, to understand their genetic variation and geographic population structure. The larger extent of net nucleotide substitution between Korean and Japanese samples, shown by intrasample clustering of the Korean samples in neighbor-joining phylogram, indicated that the Korean sample represented a genetically distinct population. Within the Japanese Archipelago, intrasample nucleotide diversities were high and masked intersample nucleotide divergences, with no obvious correspondence between genetic (net nucleotide substitution) and geographical distances. This may imply that at the mitochon drial DNA level there was no genetic differentiation among samples and they belonged to a single large population. However, minute but significant heterogeneities in the degree of intrasample nucleotide diversity and the frequency of nucleotide substitution at specific sites among Japanese Archipelago sam ples suggests the population is substructured as a metapopulation.