The distribution patterns of loaches (Teleostei: Cobitoidea) were revealed in the River East Tiaoxi in China. Eight loach species (Cobitis sinensis, C. dolichorhynchus, C. laterimaculata, Misgurnus anguillicaudatus, Paramisgurnus dabryanus, Leptobotia tchangi, Vanmanenia pingchowensis and V. stenosoma) were found in field surveys at 90 sites. A macroscale analysis of the geographical distribution showed that related species were segregated in accordance with longitudinal alterations along the river course. M. anguillicaudatus was widely distributed from the middle reaches to upstream of the river whereas the related species, P. dabryanus, was distributed only downstream. Three spined loaches, namely C. dolichorhynchus, C. sinensis, and C. laterimaculata, were distributed in the middle reaches, the middle to upstream reaches, and the upstream section of the river, respectively. The distribution of V. pingchowensis was further upper stream than that of V. stenosoma in the upstream section. More detailed microscale analysis revealed that L. tchangi and the two Vanmanenia species, V. stenosoma and V. pingchowensis were mostly found in the ‘Riffle’ (lotic) habitats, whereas the two spined loaches, C. laterimaculata and C. sinensis preferred the ‘Pool’ (lentic) habitats. These results demonstrated that related loach species preferred similar habitat units in the River East Tiaoxi system.
The distribution patterns of seven Cobitis species are analysed, namely, C. takatsuensis, C. biwae, the yamato complex, the Kyushu form of C. striata (small race), C. striata (middle race), the Hakata form of C. striata (middle race), and the Onga form of C. striata (middle race) in the northern Kyushu Island, Japan. C. takatsuensis is distributed in the upstream areas of some rivers in the northeastern part of the island. The yamato complex is widely distributed in the northern part of the island. The other five species are distributed in five areas separated by mountains. Although the yamato complex and the four striata complex species are often distributed in the same river system, the former inhabit upstream areas, while the latter inhabit the downstream reaches. The results of this study reveal that habitat fragmentation by mountains and the difference in longitudinal distribution lead to this complicated distribution pattern.
A 13-landmark morphometric system was used for 617 specimens to investigate the hypothesis of species differentiation
among Cobitis keyvani, Cobitis faridpaki and an unknown Cobitis sp. population from the River Babolrud in the southern Caspian Sea basin. Univariate analysis of variance showed significant differences among the means of the three groups for 41 out of 78 standardized morphometric measurements. In discriminant function analysis, the overall assignment of individuals into their original groups was 58.0 %. The proportions of individuals correctly classified into their original groups were 58.1 %, 64.7 % and 44.1 % for Cobitis sp., C. faridpaki and C. keyvani,respectively. Principal component analysis (PCA) and canonical variates analysis (CVA) confirmed the significant difference among these populations (λ de Wilks = 0.42, P = 0). The CVA scatter plot showed 617 specimens grouped into three distinct areas with some overlap. Clustering based on Euclidean distances among the groups of centroids using an UPGMA indicated segregation of the three populations into two distinct clusters: Cobitis sp. and C. faridpaki in one group and C. keyani in other group. Also the unknown population of spined loach from the River Babolrud was recognized as C. faridpaki and the river as a new habitat for the species.