Genetic Heterogeneity Reveals On-Going Speciation And
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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by University of Debrecen Electronic Archive Genetic Heterogeneity Reveals On-Going Speciation and Cryptic Taxonomic Diversity of Stream-Dwelling Gudgeons (Teleostei, Cyprinidae) in the Middle Danubian Hydrosystem (Hungary) Pe´ter Taka´cs1*,Pe´ter Bihari2, Tibor Ero˝s1, Andra´s Speczia´r1, Ildiko´ Sziva´k1,Pe´ter Bı´ro´ 1, Eszter Csoma3 1 Department of Hydrozoology, Balaton Limnological Institute, MTA Centre for Ecological Research, Tihany, Hungary, 2 Institute of Genetics, MTA Biological Research Centre, Szeged, Hungary, 3 Department of Medical Microbiology, University of Debrecen, Debrecen, Hungary Abstract Although stream-dwelling gudgeons (Cyprinidae, genus: Gobio) are widespread in Central Europe, the taxonomy of this group and the distribution of its species are still unexplored in detail. The aims of our study are to ascertain taxonomic composition and distribution of the former Gobio gobio superspecies in the inner area of the Carpathian Basin. Since the presence of cryptic species is suspected in this area, we examined the taxonomic and phylogenetic relationships of Central European Gobio taxa by sequencing the mitochondrial DNA control region (mtCR). Additionally, we characterized the genetic structure of 27 stream-dwelling gudgeon populations of this area by Amplified Fragment Length Polymorphism (AFLP). Results of mtCR analysis proved the presence of three species already known as G. obtusirostris (dominant in NW- Hungary), G. gobio (sporadic) and G. carpathicus (sporadic). Additionally, the analysis revealed the existence of one doubtful taxon, G. sp1 (dominant in NE-Hungary), and a new isolated haplogroup (dominant in SW-Hungary). Although Network analysis showed significant detachment among haplogroups, their genetic distances were quite small. Therefore Bayesian phylogenetic analysis showed weak nodal support for the branching pattern both for newly described haplotypes, and for the already accepted species. AFLP data showed distinct population structure and a clear pattern of isolation was revealed by distance of stocks. At the same time, level of separation was not affected by the altitudinal position of sites. Moreover we found three major clusters of populations which were separated according to hydrographic regions, and corresponded to the findings of mtCR analysis. Our results suggest the on-going speciation of gudgeons in the Carpathian Basin, however the separation of haplogroups seems to only be an intermediate phase. The discovered natural pattern seems to be only slightly influenced by anthropogenic impacts. Additionally our results put into question the suitability of the recently accepted within Gobio genus taxonomy. Citation: Taka´cs P, Bihari P, Ero˝s T, Speczia´r A, Sziva´k I, et al. (2014) Genetic Heterogeneity Reveals On-Going Speciation and Cryptic Taxonomic Diversity of Stream-Dwelling Gudgeons (Teleostei, Cyprinidae) in the Middle Danubian Hydrosystem (Hungary). PLoS ONE 9(5): e97278. doi:10.1371/journal.pone.0097278 Editor: Jesus E. Maldonado, Smithsonian Conservation Biology Institute, United States of America Received July 14, 2013; Accepted April 18, 2014; Published May 13, 2014 Copyright: ß 2014 Taka´cs et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The study was supported by the Hungarian Scientific Research Fund (OTKA-NKTH CNK 80140). ‘‘The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript’’. Competing Interests: The authors have declared that no competing interests exist. * E-mail: [email protected] Introduction species (i.e. on-going speciation) [10], [11], [12], [13], [14]. Such phenomena are more likely to occur in organisms with limited Freshwaters are exceedingly diverse ecosystems, but at the same dispersion ability and/or in organisms living in separated or time they are extremely sensitive to habitat degradation and narrowly connected habitats [15], [16], [17]. Many stream- pollution [1]. Accurately quantifying their taxonomic and dwelling fishes have specific environmental needs and therefore functional diversity is a fundamental requirement of conservation form discrete populations, not only between geographical areas biological, ecological, biogeographical, and macroevolutionary with separated catchment systems, but also between closely related research [2], [3], [4]. However, when species are not clearly sites of the same catchment [18], [19], [20], [21]. These isolated distinguishable by the conventional methods using ecological and fish populations may then genetically differentiate with time, morphological traits, have highly similar environmental needs and although they may still maintain their similar morphological reveal a high level of phenotypic plasticity, then estimates of appearance and ecological function [22]. However, this process is biodiversity and ecosystem functioning will be biased [5], [6], [7], not yet fully understood in seemingly well connected catchment [8]. systems. With the increasing use of molecular techniques, it has become The type species of the Gobioninae subfamily (Fam: Cyprinidae), evident that many species formerly believed to have widespread the common gudgeon Gobio gobio Linnaeus (1758), was known as geographical distribution can in fact be divided into numerous the most widely distributed lentic gudgeon species in West Eurasia more or less discrete entities -so called cryptic or sibling species by Mayr [9]- or represent genetic gradients between separating PLOS ONE | www.plosone.org 1 May 2014 | Volume 9 | Issue 5 | e97278 Cryptic Speciation of Stream-Dwelling Gobio [23]. However, the high between and within population morpho- 3714-2/2009, 14/1237/2/2010, 14/881/5/2011, 14/678-9/ logical variability of this taxon [24] resulted a long-standing debate 2012). Fish collected for this study were narcotized using clove regarding its taxonomical status [25], [26]. As a result, numerous oil. After fin tissue sampling, when they regained consciousness, forms/varietas/subspecies were described, nearly all from larger they were returned to the wild. Field studies did not involve fish catchment areas within its range (e.g. [23]). Recent genetic studies that were endangered (The IUCN Red List of Threatened Species have raised some of the former subspecies to species level and v. 2013.1; www.iucnredlist.org). several new species have been described as well [27], [28] [29], [30], [31], [32]. However, the taxonomic and genetic status of Study Area gudgeon populations in the Carpathian Basin is still unclear. Gobio All sampling sites were situated in the inner area of the gobio was considered a common species in the waters of the Carpathian Basin, which belongs to the drainage system of the Carpathian Basin for a long time [33], [34]. On the contrary, Danube River. Based on its topographic characteristics, the recent studies [31], [35] excluded the Carpathian Basin from the Hungarian part of Middle Danubian hydrosystem can be divided potential range of G. gobio and suggested the occurrence of the into two larger catchments and ten smaller sub-catchments Danube gudgeon, Gobio obtusirostris Valenciennes (1842) in the (Table 1, Figures 1 and 2). The hydrography of this area is western region of the basin, and the Carpathian gudgeon, Gobio biaxial. From the western region, all watercourses empty into the carpathicus Vladykov (1925) in the drainage system of River Tisza. Danube River. The eastern part of the country belongs to the Furthermore, Mendel et al. [31] indicated the presence of a drainage system of the Tisza River, which is the largest tributary of ‘‘species’’ (sic!: Gobio sp1) from the catchment of River Tisza, but the Danube (157 000 km2 catchment area). The structure of this the taxonomic position of this newly described taxon has not yet drainage system is dendritic, with the Tisza River forming the been firmly established. It is also important to note that the central axis. All the studied watercourses connected to the middle findings of Kottelat and Freyhof [35] are based exclusively on data section of the River Tisza [42], therefore this region was not from the literature. Moreover, although the study of Mendel et al. differentiated further. The hydrography of the Danubian system is [31] is the most comprehensive genetic study on the Middle more complicated. This system consists of three comparatively European Gobio species to date, it included only a very limited isolated subsystems: North, Middle and South Danubian regions number of samples from the Carpathian Basin and furthermore all (Table 1). North Danubian region is formed by the drainages of of those samples originated from the edges of this region. The River Ra´ba (Raab), River Ipoly (Ipel) and by the drainages of above mentioned Gobio taxa (i.e. G. gobio, G. obtusirostris, G. some direct inflowing streams. Middle Danubian catchment carpathicus and G. sp1) are morphologically very similar [35], [36] originally joined to the River Danube through a marshy area. and thus their distribution and ecology cannot be explored without Until the construction of the Sio´ canal at the end of the 19th molecular justification [24]. Furthermore, recent studies on G. century, there was only intermittent connection between