The genetic structure of Squalidus multimaculatus revealing the historical pattern of serial colonization on the tip of East Asian continent

Phylogeography of the Korean endemic Coreoleuciscus (Cypriniformes: Gobionidae): the genetic evidence of colonization through Eurasian continent to the Korean Peninsula during Late Plio-Pleistocene

Background

Freshwater endemism is thought to have been formed through the vicariance of connected water systems or the process by which ancestral populations colonized specific areas. The Korean Peninsula is well recognized for its high level of freshwater endemism with about 40% of freshwater fish species being endemic.

Objective

In this study, we attempted to reconstruct the process of speciation and phylogenetic dispersal of Coreoleuciscus species, which is endemic in the Korean Peninsula.

Methods

We used fossil-calibrated divergence time estimation and ancestral distributional reconstruction to infer phylogeographic reconstruction of Coreoleuciscus based on mitochondrial cytochrome c oxidate subunit I (COI) sequences (1551 bp).

Results

Our phylogeographic analysis based on a total of 626 individuals revealed that the two Coreoleuciscus species have originated from the independent colonization of different lineages in the ancestral populations, probably during the Late Plio-Pleistocene. The full-scale expansion of Coreoleuciscus populations appears to have taken place after major river structures were completed on the Korean Peninsula. We also provided evidence that the common ancestors of Coreoleuciscus was distributed in Eastern Eurasian continent and subsequently dispersed into the tip of East Asia. High genetic diversity was mainly concentrated in large drainage populations, while small populations showed an monomorphism, which could give important implications for planning the conservation and management of Coreoleuciscus.

Conclusions

The phylogenetic background of the rheophilic Coreoleuciscus species can be explained by the colonizer hypothesis that the endemic freshwater fish originated from the common ancestor in continental region.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13258-022-01243-y.

Molecular phylogenetic, population genetic and demographic studies of Nodularia douglasiae and Nodularia breviconcha based on CO1 and 16S rRNA

Freshwater mussels belonging to the genus Nodularia (Family Unionidae) are known to be widely distributed in East Asia. Although phylogenetic and population genetic studies have been performed for these species, there still remain unresolved questions in their taxonomic status and biogeographic distribution pathways. Here, the nucleotide sequences of CO1 and 16S rRNA were newly determined from 86 N. douglasiae and 83 N. breviconcha individuals collected on the Korean Peninsula. Based on these data, we revealed the following results: (1) N. douglasiae can be divided into the three genetic clades of A (only found in Korean Peninsula), B (widely distributed in East Asia), and C (only found in the west of China and Russia), (2) the clade A is not an independent species but a concrete member of N. douglasiae given the lack of genetic differences between the clades A and B, and (3) N. breviconcha is not a subspecies of N. douglasiae but an independent species apart from N. douglasiae. In addition, we suggested the plausible scenarios of biogeographic distribution events and demographic history of Nodularia species.

Evidence of an ancient connectivity and biogeodispersal of a bitterling species, Rhodeus notatus, across the Korean Peninsula

The modern-day distribution of freshwater fishes throughout multiple rivers is likely the result of past migration during times when currently separate drainages were once connected. Here, we used mitochondrial and microsatellite analyses for 248 individuals of Rhodeus notatus collected from seven different rivers to obtain better understand historical gene flow of freshwater fish on the Korean Peninsula. Based on our phylogenetic analyses, this Korean species originated through the paleo-Yellow River from China and first colonized near the west coast. These genetic data also provided evidence of estuary coalescences among the rivers flowing to the west and southwest coast on well-developed continental shelf. In addition, the pattern of population structure revealed the biogeodispersal route from the west coast to the south coast. It could be inferred that massive migration was not involved in the formation of southern populations, since the signature of historical genetic drift was clearly observed. Our study is the first genetic attempt to confirm hypotheses describing the migration of freshwater species towards the end of East Asia, which have previously been developed using only geological reasoning.

Fish diversification at the pace of geomorphological changes: evolutionary history of western Iberian Leuciscinae (Teleostei: Leuciscidae) inferred from multilocus sequence data

The evolutionary history of western Iberian Leuciscinae, obligatory freshwater fish, is directly linked to the evolution of the hydrographic network of the Iberian Peninsula after its isolation from the rest of Europe, which involved dramatic rearrangements such as the transition from endorheic lakes to open basins draining to the Atlantic. Previous phylogenetic research on western Iberian leuciscines, using mainly mitochondrial DNA and more recently one or two nuclear genes, has found contradictory results and there remain many unresolved issues regarding species relationships, taxonomy, and evolutionary history. Moreover, there is a lack of integration between phylogenetic and divergence time estimates and information on the timing of geomorphological changes and paleobasin rearrangements in the Iberian Peninsula. This study presents the first comprehensive fossil-calibrated multilocus coalescent species tree of western Iberian Leuciscinae (including 14 species of Achondrostoma, Iberochondrostoma, Pseudochondrostoma and Squalius endemic to the Iberian Peninsula, seven of which endemic to Portugal) based on seven nuclear genes, and from which we infer their biogeographic history by comparing divergence time estimates to known dated geological events. The phylogenetic pattern suggests slow-paced evolution of leuciscines during the Early-Middle Miocene endorheic phase of the main Iberian river basins, with the shift to exorheism in the late Neogene-Quaternary allowing westward dispersals that resulted in many cladogenetic events and a high rate of endemism in western Iberia. The results of this study also: (i) confirm the paraphyly of S. pyrenaicus with respect to S. carolitertii, and thus the possible presence of a new taxon in the Portuguese Tagus currently assigned to S. pyrenaicus; (ii) support the taxonomic separation of the Guadiana and Sado populations of S. pyrenaicus; (iii) show the need for further population sampling and taxonomic research to clarify the phylogenetic status of A. arcasii from the Minho basin and of the I. lusitanicum populations in the Sado and Tagus basins; and (iv) indicate that A. occidentale, I. olisiponensis and P. duriensis are the most ancient lineages within their respective genera.