Genetic Diversity in the Paramecium aurelia Species Complex

Department of Biology, Indiana University, USA.
Molecular Biology and Evolution (Impact Factor: 9.11). 12/2008; 26(2):421-31. DOI: 10.1093/molbev/msn266
Source: PubMed


Current understanding of the population genetics of free-living unicellular eukaryotes is limited, and the amount of genetic variability in these organisms is still a matter of debate. We characterized-reproductively and genetically-worldwide samples of multiple Paramecium species belonging to a cryptic species complex, Paramecium aurelia, whose species have been shown to be reproductively isolated. We found that levels of genetic diversity both in the nucleus and in the mitochondrion are substantial within groups of reproductively compatible P. aurelia strains but drop considerably when strains are partitioned according to their phylogenetic groupings. Our study reveals the existence of discrepancies between the mating behavior of a number of P. aurelia strains and their multilocus genetic profile, a controversial finding that has major consequences for both the current methods of species assignment and the species problem in the P. aurelia complex.

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Available from: Francesco Catania
    • "It was not possible to apply these markers or markers which were previously used in P. aurelia spp. studies (e.g., Catania, Wu rmser, Potekhin, Przybo s, & Lynch, 2009) in all of the tested species, probably due to interspecific differences. The details of the new markers are presented in Tables S1, S2 and the supplementary material. "
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    ABSTRACT: Ciliates (Protista) have a complex species structure, which means that in several genera the morphological species are differentiated into cryptic species with isolated gene pools (called syngens). Problems of speciation are well known in the genus Paramecium, and especially in the P. aurelia sibling (cryptic) species complex within it. However, the problem of the existence of such species within P. jenningsi was, until recently, still unsolved. Here we present the results of studies based on an analysis of 16 loci (both nuclear and mitochondrial), strain crosses and cytological preparations. The obtained data allowed us not only to study relationships of the P. jenningsi complex and other morphospecies within the Paramecium subgenus, but also to confirm the existence of three isolated reproductive groups within the former P. jenningsi and to propose binominal names for each of them: P. primjenningsi, P. bijenningsi, and P. trijenningsi. In our view, the studied species meet the criteria of a species complex because they can be differentiated based on strain crosses and molecular characteristics, but they cannot be differentiated based on morphological features alone.
    No preview · Article · Mar 2016 · Systematics and Biodiversity
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    • "Based on macronuclear genome sequences analyses, McGrath et al. showed that P. sexaurelia diverged immediately following or concurrently with the recent WGD. Similarly, that species was revealed to occupy the most distant position in previous studies (Catania et al. 2009; Coleman 2005) as well as in the present work. Although currently there are no genome data for P. sonneborni , P. jenningsi and P. schewiakoffi, on the basis of the nuclear marker analysis (Fig. 4) and assumptions concerning the time of P. sexaurelia separation (McGrath et al. 2014), we hypothesize that these three species (P. "
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    ABSTRACT: The demarcation of boundaries between protist species is often problematic because of the absence of a uniform species definition, the abundance of cryptic diversity, and the occurrence of convergent morphology. The ciliates belonging to the Paramecium aurelia complex, consisting of 15 species, are a good model for such systematic and evolutionary studies. One member of the complex is P. sonneborni, previously known only from one stand in Texas (USA), but recently found in two new sampling sites in Cyprus (creeks running to Salt Lake and Oroklini Lake near Larnaca). The studied Paramecium sonneborni strains (from the USA and Cyprus) reveal low viability in the F1 and F2 generations of interstrain hybrids and may be an example of ongoing allopatric speciation. Despite its molecular distinctiveness, we postulate that P. sonneborni should remain in the P. aurelia complex, making it a paraphyletic taxon. Morphological studies have revealed that some features of the nuclear apparatus of P. sonneborni correspond to the P. aurelia spp. complex, while others are similar to P. jenningsi and P. schewiakoffi. The observed discordance indicates rapid splitting of the P. aurelia-P. jenningsi-P. schewiakoffi group, in which genetic, morphological, and molecular boundaries between species are not congruent. Copyright © 2015 Elsevier GmbH. All rights reserved.
    Full-text · Article · Jul 2015 · Protist
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    • "Many DNA sequencing methods are available to analyse protist community composition (Hajibabaei et al. 2011; Zufall, Dimon & Doerder 2013), to characterize genetic diversity of species complexes (e.g. Catania et al. 2009), or to understand the evolution of genes and genomes (e.g. Brunk et al. 2003; Moradian et al. 2007). "
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    ABSTRACT: 1.Laboratory microcosm experiments using protists as model organisms have a long tradition and are widely used to investigate general concepts in population biology, community ecology and evolutionary biology. Many variables of interest are measured in order to study processes and patterns at different spatiotemporal scales and across all levels of biological organization. This includes measurements of body size, mobility, or abundance, in order to understand population dynamics, dispersal behaviour, and ecosystem processes. Also, a variety of manipulations are employed, such as temperature changes or varying connectivity in spatial microcosm networks. 2.Past studies, however, have used varying methods for maintenance, measurement, and manipulation, which hinders across-study comparisons and meta-analyses, and the added value they bring. Furthermore, application of techniques such as flow-cytometry, image and video analyses, and in-situ environmental probes provide novel and improved opportunities to quantify variables of interest at unprecedented precision and temporal resolution. 3.Here, we take the first step towards a standardization of well-established and novel methods and techniques within the field of protist microcosm experiments. We provide a comprehensive overview of maintenance, measurement, and manipulation methods. An extensive supplement contains detailed protocols of all methods, and these protocols also exist in a community updateable online repository. 4.We envision that such a synthesis and standardization of methods will overcome shortcomings and challenges faced by past studies, and also promote activities such as meta-analyses and distributed experiments conducted simultaneously across many different laboratories at a global scale.
    Full-text · Article · Feb 2015 · Methods in Ecology and Evolution
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