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      Dispersal and gene flow in free-living marine nematodes

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          Abstract

          Dispersal and gene flow determine connectivity among populations, and can be studied through population genetics and phylogeography. We here review the results of such a framework for free-living marine nematodes. Although field experiments have illustrated substantial dispersal in nematodes at ecological time scales, analysis of the genetic diversity illustrated the importance of priority effects, founder effects and genetic bottlenecks for population structuring between patches <1 km apart. In contrast, only little genetic structuring was observed within an estuary (<50 km), indicating that these small scale fluctuations in genetic differentiation are stabilized over deeper time scales through extensive gene flow. Interestingly, nematode species with contrasting life histories (extreme colonizers vs persisters) or with different habitat preferences (algae vs sediment) show similar, low genetic structuring. Finally, historical events have shaped the genetic pattern of marine nematodes and show that gene flow is restricted at large geographical scales. We also discuss the presence of substantial cryptic diversity in marine nematodes, and end with highlighting future important steps to further unravel nematode evolution and diversity.

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          Most cited references78

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          Cryptic species as a window on diversity and conservation.

          The taxonomic challenge posed by cryptic species (two or more distinct species classified as a single species) has been recognized for nearly 300 years, but the advent of relatively inexpensive and rapid DNA sequencing has given biologists a new tool for detecting and differentiating morphologically similar species. Here, we synthesize the literature on cryptic and sibling species and discuss trends in their discovery. However, a lack of systematic studies leaves many questions open, such as whether cryptic species are more common in particular habitats, latitudes or taxonomic groups. The discovery of cryptic species is likely to be non-random with regard to taxon and biome and, hence, could have profound implications for evolutionary theory, biogeography and conservation planning.
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            Microsatellites in different eukaryotic genomes: survey and analysis.

            We examined the abundance of microsatellites with repeated unit lengths of 1-6 base pairs in several eukaryotic taxonomic groups: primates, rodents, other mammals, nonmammalian vertebrates, arthropods, Caenorhabditis elegans, plants, yeast, and other fungi. Distribution of simple sequence repeats was compared between exons, introns, and intergenic regions. Tri- and hexanucleotide repeats prevail in protein-coding exons of all taxa, whereas the dependence of repeat abundance on the length of the repeated unit shows a very different pattern as well as taxon-specific variation in intergenic regions and introns. Although it is known that coding and noncoding regions differ significantly in their microsatellite distribution, in addition we could demonstrate characteristic differences between intergenic regions and introns. We observed striking relative abundance of (CCG)(n)*(CGG)(n) trinucleotide repeats in intergenic regions of all vertebrates, in contrast to the almost complete lack of this motif from introns. Taxon-specific variation could also be detected in the frequency distributions of simple sequence motifs. Our results suggest that strand-slippage theories alone are insufficient to explain microsatellite distribution in the genome as a whole. Other possible factors contributing to the observed divergence are discussed.
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              RADSeq: next-generation population genetics.

              Next-generation sequencing technologies are making a substantial impact on many areas of biology, including the analysis of genetic diversity in populations. However, genome-scale population genetic studies have been accessible only to well-funded model systems. Restriction-site associated DNA sequencing, a method that samples at reduced complexity across target genomes, promises to deliver high resolution population genomic data-thousands of sequenced markers across many individuals-for any organism at reasonable costs. It has found application in wild populations and non-traditional study species, and promises to become an important technology for ecological population genomics.
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                Author and article information

                Journal
                Front Zool
                Front. Zool
                Frontiers in Zoology
                BioMed Central
                1742-9994
                2013
                28 January 2013
                : 10
                : 1
                Affiliations
                [1 ]Department of Biology, Marine Biology section, Ghent University, Krijgslaan 281, S8, 9000, Ghent, Belgium
                [2 ]CeMoFE, Ghent University, K.L. Ledeganckstraat 35, 9000, Ghent, Belgium
                [3 ]Royal Belgian Institute of Natural Sciences (Joint Experimental Molecular Unit), Vautierstraat 29, 1000, Brussels, Belgium
                [4 ]Department of Biology, Evolutionary Biology Group, University of Antwerp, Groenenborgerlaan 171, 2020, Antwerp, Belgium
                Article
                1742-9994-10-1
                10.1186/1742-9994-10-1
                3567977
                23356547
                2ee379a3-e189-4c34-a792-b34f8f06fbf1
                Copyright ©2013 Derycke et al.; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 3 September 2012
                : 21 January 2013
                Categories
                Review

                Animal science & Zoology
                connectivity,cryptic species,dispersal,gene flow,life history,marine nematodes,phylogeography,population genetics

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