Population structure of a microparasite infecting Daphnia: spatio-temporal dynamics

Background: Detailed knowledge of spatial and temporal variation in the genetic population structure of hosts and parasites is required for understanding of host - parasite coevolution. As hot-spots of contemporary coevolution in natural systems are difficult to detect and long-term studies are restricted to few systems, additional population genetic data from various host - parasite systems may provide important insights into the topic. This is particularly true for parasites, as these players have been under-investigated so far due to the lower availability of suitable molecular markers. Here, we traced genetic variation (based on sequence variants in the internal transcribed spacer region, ITS) among seven geographically isolated populations of the ichthyosporean Caullerya mesnili, a common microparasite of the cladoceran Daphnia (here, the D. longispina hybrid complex). At three sites, we also studied parasite genetic variation over time (three to four sampling points) and tested for associations between parasite genotypes and host species. Results: Parasite (and host) populations were significantly structured across space, indicating limited dispersal. Moreover, the frequency of parasite genotypes varied significantly over time, suggesting rapid evolutionary change in Caullerya. However, the distribution of parasite genotypes was similar across different host species, which might in turn have important consequences for parasite epidemiology. Conclusions: The approach proposed here can be applied to track spatial and temporal changes in the population structure of other microparasite species for which sequence variation in the ITS or other highly variable genome regions has been documented but other types of polymorphic markers are lacking. Screening of parasite sequence variants allows for reliable detection of cross-species infections and, using advanced sequencing techniques in the near future, for detailed studies of parasite evolution in natural host - parasite systems

New possibilities arise for studies of hybridization: SNP-based markers for the multi-species Daphnia longispina complex derived from transcriptome data

In order to trace community dynamics and reticulate evolution in hybrid species complexes, long-term comparative studies of natural populations are necessary. Such studies require the development of tools for fine-scale genetic analyses. In the present study, we developed species-diagnostic SNP-based markers for hybridizing freshwater crustaceans: the multispecies Daphnia longispina complex. Specifically, we took advantage of transcriptome data from a key species of this hybrid complex, the annotated genome of a related Daphnia species and well-defined reference genotypes from three parental species. Altogether eleven nuclear loci with several species-specific SNP sites were identified in sequence alignments of these reference genotypes from three parental species and their interspecific hybrids. A PCR-RFLP assay was developed for cost-efficient large population screening by SNP-based genotyping. Taxon assignment by RFLP patterns was nearly perfectly concordant with microsatellite genotyping across several screened populations from Europe. Finally, we were able to amplify two short regions of these loci in formaldehyde-preserved samples dating back to the year 1960. The species-specific SNP-based markers developed here provide valuable tools to study hybridization over time, including the long-term impact of various environmental factors on hybridization and biodiversity changes. SNP-based genotyping will finally allow eco-evolutionary dynamics to be revealed at different time scale

Daphnia parasite dynamics across multiple Caullerya epidemics indicate selection against common parasite genotypes

Studies of parasite population dynamics in natural systems are crucial for our understanding of host–parasite coevolutionary processes. Some field studies have reported that host genotype frequencies in natural populations change over time according to parasite-driven negative frequency-dependent selection. However, the temporal patterns of parasite genotypes have rarely been investigated. Moreover, parasite-driven negative frequency-dependent selection is contingent on the existence of genetic specificity between hosts and parasites. In the present study, the population dynamics and host-genotype specificity of the ichthyosporean Caullerya mesnili, a common endoparasite of Daphnia water fleas, were analysed based on the observed sequence variation in the first internal transcribed spacer (ITS1) of the ribosomal DNA. The Daphnia population of lake Greifensee (Switzerland) was sampled and subjected to parasite screening and host genotyping during C. mesnili epidemics of four consecutive years. The ITS1 of wild-caught C. mesnili-infected Daphnia was sequenced using the 454 pyrosequencing platform. The relative frequencies of C. mesnili ITS1 sequences differed significantly among years: the most abundant C. mesnili ITS1 sequence decreased and rare sequences increased over the course of the study, a pattern consistent with negative frequency-dependent selection. However, only a weak signal of host-genotype specificity between C. mesnili and Daphnia genotypes was detected. Use of cutting edge genomic techniques will allow further investigation of the underlying micro-evolutionary relationships within the Daphnia–C. mesnili system

反応蒸留プロセスの合成と動的最適化

京都大学0048新制・課程博士博士(工学)甲第8343号工博第1908号新制||工||1168(附属図書館)UT51-2000-F247京都大学大学院工学研究科化学工学専攻(主査)教授 橋本 伊織, 教授 谷垣 昌敬, 教授 田門 肇学位規則第4条第1項該当Doctor of EngineeringKyoto UniversityDA

Data from: Capturing the population structure of microparasites: using ITS-sequence data and a pooled DNA approach

The internal transcribed spacer (ITS) region of nuclear ribosomal DNA is a common marker not only for the molecular identification of different taxa and strains, but also for the analysis of population structure of wild microparasite communities. Importantly, the multicopy nature of this region allows the amplification of low-quantity samples of the target DNA, a common problem in studies on unicellular, unculturable microparasites. We analysed ITS sequences from the protozoan parasite Caullerya mesnili (class Ichthyosporea) infecting waterflea (Daphnia) hosts, across several host population samples. We showed that analysing representative ITS-types [as identified by statistical parsimony network analysis (SPN)] is a suitable method to address relevant polymorphism. The spatial patterns were consistent regardless of whether parasite DNA was extracted from individual hosts or pooled host samples. Remarkably, the efficiency in detecting different sequence types was even higher after sample pooling. As shown by simulations, an easily manageable number of sequences from pooled DNA samples are sufficient to resolve the spatial population structure in this system. In summary, the ITS region analysed from pooled DNA samples can provide valuable insights into the spatial and temporal dynamics of microparasites. Moreover, the application of SPN analysis is a good alternative to the well-established neighbour-joining method (NJ) for the identification of representative ITS-types. SPN can even outperform NJ by joining most of the singleton sequences to representative sequence clusters

caullerya_ITS_alignment

caullerya_ITS_alignmen

New possibilities arise for studies of hybridization: SNP-based markers for the multi-species Daphnia longispina complex derived from transcriptome data

In order to trace population community dynamics and reticulate evolution in hybrid species complexes, long-term comparative studies of natural populations are necessary and thus, tools for fine-scale genetic analyses are needed. In the present study, we developed species-diagnostic SNP markers for hybridizing freshwater crustaceans: the multispecies Daphnia longispina complex. Specifically, we took advantage of transcriptome data from a key species of this hybrid complex, the annotated genome of a related Daphnia species and well-defined reference genotypes from three parental species. Altogether eleven nuclear loci with several species-specific SNP sites were identified in sequence alignments of 22 individuals of three parental species and their hybrids. A PCR-RFLP assay was developed for cost-efficient large population screening by SNP-genotyping. Taxon assignment by RFLP-patterns was nearly perfectly concordant with microsatellite genotyping across several screened populations from Europe. Finally, we were able to amplify two short regions of these loci in formaldehyde-preserved samples dating back to the year 1960. The species-specific SNP markers developed here provide valuable tools to study hybridization over time, including the long-term impact of various environmental factors on hybridization and biodiversity changes. SNP-based genotyping will finally allow for revealing eco-evolutionary dynamics at different time scales

"PROGRAMA SOCIAL JUNTOS EN EDUCACIÓN Y SALUD DE LOS NIÑOS Y NIÑAS DE LAS FAMILIAS BENEFICIARIAS EN EL CENTRO POBLADO DE PUEBLO LIBRE - HUANCAVELICA"

TesisEl presente proyecto de investigación esta orientado al estudio del impacto del programa social Juntos en educación y salud de los niños y niñas de las familias beneficiarias en el Centro Poblado de Pueblo Libre - Huancavelica "Estudio realizado por IGNACIO CRUZ Serafín y LOAYZA VALENZUELA, Fèlix con el objetivo especifico de identificar el programa social Juntos en el incremento de la matricula, asistencia y la deserción escolar; Describir el acceso de los beneficiarios del Programa Juntos a servicios de salud en el Centro Poblado de Pueblo Libre - Huancavelica y analizar el impacto de programas que articulen con el programa Juntos en el mejoramiento de la calidad de vida de los beneficiarios del Centro Poblado de Pueblo Libre - Huancavelica,. El hipótesis que se plantea es el impacto de educación y salud de los niños y niñas, de las familias beneficiarias del Programa Social Juntos en el Centro Poblado de Pueblo Libre - Huancavelica, mejorò la calidad de vida de los beneficiarios. Para el cual se utilizara el método descriptivo, comparativo y estadístico; también se utilizara el diseño descriptivo causal. El instrumento que se utilizara es cuestionario de encuestas, con preguntas abiertas y cerrados; el cual fue aplicado a una población de 40 beneficiarios del programa Juntos. Se emplearan medidas cuantitativas y cualitativas. Los resultados son: El Programa JUNTOS es considerado por los beneficiarios como un soporte para el mejoramiento de su calidad vida y de sus familias. La gran mayoría de recurso se destina a alimentación el cual mejorò de regular de 17.5% a bueno 82.5% con calidad de alimentos con mayor contenido proteico. En salud, practica de higienes adecuadas, prevención de enfermedades y control de crecimiento y desarrollo de los niños y niñas y en general, la atención de salud mediante SIS con el apoyo del programa