Around or across the Carpathians: colonization model of the Danube basin inferred from genetic diversification of stone loach (Barbatula barbatula) populations

Abstract

Despite increasing information about postglacial recolonization of European freshwater systems, very little is known about pre-Pleistocene history. We used data on the recent distribution and phylogenetic relationships of stone loach mitochondrial lineages to reconstruct the initial colonization pattern of the Danube river system, one of the most important refuges for European freshwater ichthyofauna. Fine-scale phylogeography of the Danubian populations revealed five highly divergent lineages of pre-Pleistocene age and suggested the multiple origin of the Danubian stone loach. The mean sequence divergence among lineages extended from 7.0% to 13.4%, which is the highest intraspecific divergence observed so far within this river system. Based on the phylogeographical patterns, we propose the following hypothesis to relate the evolution and dispersal of the studied species with the evolution of the Danube river system and the Carpathian Mountains: (i) during the warmer period in the Miocene, the areas surrounding the uplifting Alps and Carpathians served as mountainous refuges for cold-water adapted fish and promoted the diversification of its populations, and (ii) from these refuges, colonization of the emerging Danube river system may have taken place following the retreat of the Central Paratethys. Co-existence of highly divergent mtDNA lineages in a single river system shows that range shifts in response to climatic changes during the Quaternary did not cause extensive genetic homogenization in the stone loach populations. However, the wide distribution of some mtDNA lineages indicates that the Pleistocene glaciations promoted the dispersal and mixing of populations through the lowlands.

From Late Miocene to Holocene: Processes of Differentiation within the Telestes Genus (Actinopterygii: Cyprinidae)

“…Although times of divergences were found older (i.e. Pliocene) than in T. souffia , a similar pattern was also found in the cold-adapted and rheophilic Barbatula barbatula , for which populations were maintained in the upstream portion of the rivers [105]. As a corollary, the thermophilic Rhodeus amarus , a species common in lotic and lentic habitats [106], has been documented to harbor rather homogenous populations along the Danube basin.…”

Genetic Heterogeneity Reveals On-Going Speciation and Cryptic Taxonomic Diversity of Stream-Dwelling Gudgeons (Teleostei, Cyprinidae) in the Middle Danubian Hydrosystem (Hungary)

“…This premise is supported by the fact that in the case of other fish species, e.g. topmouth gudgeon - Pseudorasbora parva (Temminck & Schlegel, 1842), stone loach - Barbatula barbatula (Linnaeus, 1758), and grayling - Thymallus thymallus (Linnaeus, 1758), a similar or higher degree of differentiation among haplogroups is considered to be not more than subspecies level detachment [20], [74], [75]. In addition, some authors [76], [77] have suggested that the genetic distance of haplogroups must be greater than or equal to ten times the level of within-haplogroup differences to distinguish separate species.…”

“…Such phenomena are more likely to occur in organisms with limited dispersion ability and/or in organisms living in separated or narrowly connected habitats [15], [16], [17]. Many stream-dwelling fishes have specific environmental needs and therefore form discrete populations, not only between geographical areas with separated catchment systems, but also between closely related sites of the same catchment [18], [19], [20], [21]. These isolated fish populations may then genetically differentiate with time, although they may still maintain their similar morphological appearance and ecological function [22].…”

Species History Masks the Effects of Human-Induced Range Loss – Unexpected Genetic Diversity in the Endangered Giant Mayfly Palingenia longicauda

“…We expected strong genetic differentiation between the Danube and Rhine drainages, given that strong differentiation, and even cryptic taxa of European freshwater species are frequently discovered even in geographically close ranges, e.g. [13]–[16], [18], [32], [36], [42]–[45]. The star-like shape of the haplotype network [45]–[48], the highly significant deviations from selective neutrality, and the BSP estimates (Figure 4) all suggest an important and relatively recent increase in effective population size.…”

“…Local genetic variants and ESUs might harbor unique evolutionary potential, and provide the source of adaptation to future environmental change [9], [10]. These concerns are particularly relevant in freshwater systems, because several species show high levels of differentiation within their ranges, especially along the main catchments [11]–[13], and for species with a limited potential for overland dispersal [14]–[18]. Although existing works suggest that range losses should parallel the loss of genetic diversity [4]–[6], there is still little empirical information on the coupling of these processes, especially in freshwater species.…”