Recent studies of the distribution and diversity of freshwater zooplankton have indicated that the previously understudied Eastern Palearctic region is an important biogeographic hotspot. Here, we explored the lineage diversity and reproductive modes of the Daphnia pulex species group across China. Members of this group are often keystone species of standing water bodies and are frequently used as a model system for ecological, evolutionary and, more recently, genomic studies. We found members of the D. pulex group in seven of seventy-six Chinese water bodies examined. We analyzed their phylogenetic position using mitochondrial markers, and explored the genetic structure of six populations using microsatellite markers. Mitochondrial DNA analysis suggested the presence of two distinct species complexes in China: the D. pulex complex that has a global distribution, and an apparently endemic Eastern Palearctic D. mitsukuri complex. Microsatellite analyses of six populations suggested that three of these reproduced by cyclical parthenogenesis, as evidenced by high clonal diversity and the absence of deviations from the Hardy-Weinberg equilibrium. In contrast, three other populations showed remarkably low diversity of multilocus genotypes. This suggests an obligate parthenogenetic reproductive mode, which was confirmed in one of the populations by comparison of genotypes of Daphnia adults and dormant embryos. All presumably obligate parthenogenetic clones were heterozygous at the majority of microsatellite loci, suggesting their hybrid origin. This was further supported by analyses of a small GTPase nuclear gene (rab4), as two alleles within single individuals belonged to different clades. Interestingly, one putatively obligate parthenogenetic clone carried three distinct alleles suggesting higher ploidy and potential gene flow between the D. pulicaria and D. mitsukuri complexes. Our data show that the expansion of the D. pulex complex in the Eastern Palearctic was associated with widespread hybridization.

• MeSH
• analýza hlavních komponent MeSH
• Daphnia klasifikace   genetika   MeSH
• fylogeneze * MeSH
• genetická variace * MeSH
• haplotypy MeSH
• jezera * MeSH
• mikrosatelitní repetice genetika   MeSH
• mitochondriální DNA genetika   MeSH
• mitochondriální geny MeSH
• pravděpodobnostní funkce MeSH
• rozmnožování genetika   MeSH
• zeměpis MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Čína MeSH

The idea that hybridization promotes range expansion has received recent attention, but support from field studies is limited. We hypothesized that in the cladoceran waterflea genus Daphnia, parental species are geographically and ecologically separated, whereas hybrids occupy intermediate or occasionally extreme environments, potentially facilitating range expansion of parental species. We assessed the distribution of Daphnia dentifera, Daphnia galeata and their interspecific hybrids across 44 lakes in China (using mitochondrial and microsatellite markers), and related it to geographical and environmental lake descriptors. Parental species were geographically separated: D. dentifera occurred in western and central China, and D. galeata in eastern and central China, whereas hybrids were found in the western and central parts of the country. However, after controlling for geographical differences, the effect of environment on species distribution was strong and significant. Specifically, D. dentifera was present in high-altitude oligotrophic lakes, D. galeata in low-altitude eutrophic lakes and hybrids at intermediate to high altitudes, mainly in mesotrophic lakes. Microsatellite data indicated that hybrids were locally produced rather than having migrated from elsewhere; they probably resulted from encounters between expanding D. galeata and resident D. dentifera. The present study provides evidence that hybrids can survive in habitats that are otherwise suitable for only one of their parental species, emphasizing the importance of hybridization in expansion of species gene pools.

• MeSH
• Daphnia genetika   fyziologie   MeSH
• ekologie MeSH
• ekosystém * MeSH
• genetická variace genetika   MeSH
• hybridizace genetická MeSH
• jezera MeSH
• mikrosatelitní repetice genetika   MeSH
• mitochondriální DNA genetika   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Čína MeSH

BACKGROUND: The zooplanktonic cladocerans Daphnia, present in a wide range of water bodies, are an important component of freshwater ecosystems. In contrast to their high dispersal capacity through diapausing eggs carried by waterfowl, Daphnia often exhibit strong population genetic differentiation. Here, to test for common patterns in the population genetic structure of a widespread Holarctic species, D. galeata, we genotyped two sets of populations collected from geographically distant areas: across 13 lakes in Eastern China and 14 lakes in Central Europe. The majority of these populations were genotyped at two types of markers: a mitochondrial gene (for 12S rRNA) and 15 nuclear microsatellite loci. RESULTS: Mitochondrial DNA demonstrated relatively shallow divergence within D. galeata, with distinct haplotype compositions in the two study regions but one widely distributed haplotype shared between several of the Chinese as well as European populations. At microsatellite markers, clear separation was observed at both large (between China and Europe) and small (within Europe) geographical scales, as demonstrated by Factorial Correspondence Analyses, Bayesian assignment and a clustering method based on genetic distances. Genetic diversity was comparable between the sets of Chinese and European D. galeata populations for both types of markers. Interestingly, we observed a significant association between genetic distance and geographical distance for D. galeata populations in China but not in Europe. CONCLUSIONS: Our results indicate relatively recent spread of D. galeata across wide expanses of the Palaearctic, with one mtDNA lineage of D. galeata successfully establishing over large distances. Despite a clear differentiation of Chinese and European D. galeata at a nuclear level, the pattern of genetic variation is nevertheless similar between both regions. Overall, our findings provide insights into the genetic population structure of a cladoceran species with extremely wide geographical range.

• MeSH
• alely MeSH
• Bayesova věta MeSH
• buněčné jádro genetika   MeSH
• Daphnia genetika   MeSH
• DNA genetika   MeSH
• fylogeneze MeSH
• genetická variace * MeSH
• haplotypy genetika   MeSH
• mikrosatelitní repetice genetika   MeSH
• mitochondriální DNA genetika   MeSH
• mitochondriální geny MeSH
• mitochondrie genetika   MeSH
• populační genetika MeSH
• zeměpis MeSH
• zooplankton genetika   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Čína MeSH
• Evropa MeSH