Statistical method for testing the neutral mutation hypothesis by DNA polymorphism.

Trabajo presentado en la 113th General Meeting of the American Society for Microbiology, celebrada en Denver, Estados Unidos, del 18 al 21 de mayo de 2013

Species concept for prokaryotes

Spodoptera frugiperda, the fall armyworm, is a major economic pest throughout the Western Hemisphere of corn (maize), cotton, sorghum, and a variety of agricultural grasses and vegetable crops. Studies in the United States, the Caribbean, and Brazil demonstrated the existence of two subpopulations (previously designated "host strains") that differ in their choice of plant host. Specifically, the corn strain is preferentially found in corn and sorghum, while the rice strain is dominant in rice, turf grass, and alfalfa. However, inconsistent results were reported in surveys of fall armyworm in Argentina, with some indicating that the host plant preferences of the two strains might be compromised or even nonexistent. If correct, this would complicate efforts to control this pest by considerably expanding the range of habitats that would have to be considered as potential sources for fall armyworm infestations in specific crops. A reexamination of Argentine fall armyworm, this time with field collections rather than the laboratory colonies used in previous studies, confirmed the existence of the two strains and their host preferences. Specifically, the corn strain was consistently the majority population infesting corn and was usually so in sorghum, while the rice strain was predominant in pasture/turf grasses and alfalfa. The one outlier was a collection from rice, which had a corn strain majority. Overall, the data were generally consistent with strain behaviors observed in other areas of the Western Hemisphere.

https://bioone.org/journals/Journal-of-Economic-Entomology/volume-108/issue-5/tov203/Demonstration-Using-Field-Collections-that-Argentina-Fall-Armyworm-Populations-Exhibit/10.1093/jee/tov203.pdf

Demonstration Using Field Collections that Argentina Fall Armyworm Populations Exhibit Strain-specific Host Plant Preferences

Laboratory-reared western corn rootworms, Diabrotica virgifera virgifera, from colonies maintained at the North Central Agricultural Research Laboratory (NCARL) in Brookings, SD, are used extensively by many researchers in studies of the biology, ecology, behavior, and genetics of this major insect pest. A nondiapause colony developed through artificial selection in the early 1970s is particularly attractive for many studies because its generation time is much shorter than that of typical diapause colonies. However, the nondiapause colony has been in culture for ≈190 generations without out-crossing. We compared variation at six microsatellite loci among individuals from the NCARL nondiapause colony (≈190 generations), main diapause colony (≈22 generations), four regional diapause colonies (3–8 generations), and four wild populations. Genetic diversity was very similar among the diapause laboratory colonies and wild populations. However, the nondiapause colony showed ≈15–39% loss of diversity dep...

/pdf/genetic-diversity-in-laboratory-colonies-of-western-corn-4cw23rt4lz.pdf

Genetic diversity in laboratory colonies of western corn rootworm (Coleoptera: Chrysomelidae), including a nondiapause colony.

The Arabian rhinoceros beetle, Oryctes agamemnon arabicus (Burmeister, 1847), is an invasive species, introduced to Tunisia from the United Arab Emirates and causing serious damage to date palm trees in southern Tunisia. Considering the economic importance of this pest, it is necessary to understand the genetic diversity within and among its populations and investigate its dispersal mode. In the present study, the mitochondrial gene encoding the cytochrome oxidase subunit I (COI) was used to analyse the extent of genetic variation between samples of O. agamemnon arabicus, collected from geographically distant locations in Tunisia. A 505 bp DNA fragment, resulting from PCR amplification, was sequenced. Representative sequences were aligned, revealing nine polymorphic sites that identified eight haplotypes. Haplotype diversity (Hd) and Tajima’s D neutral test were 0.707 and –0.043, respectively, indicating a low level of mtDNA variability. The calculated gene flow value was Nm = 0.47, indicating a high amount of gene flow occurring between populations from Tozeur and those from Kebili, although both departments are separated by the Chott-El-Jerid salt lake. The presence of common haplotypes between Tozeur and Kebili as well as the clustering pattern obtained by the NJ method confirmed this result. Based on these facts and considering the limited flight of O. agamemnon arabicus and its slow reproduction, it is likely that its expansion in Tunisia was facilitated mainly by human transportation of infected offshoots.

https://bioone.org/journals/african-entomology/volume-21/issue-2/003.021.0201/Genetic-Variation-and-Invasion-Pattern-of-the-Arabian-Rhinoceros-Beetle/10.4001/003.021.0201.pdf

Genetic variation and invasion pattern of the Arabian rhinoceros beetle, Oryctes agamemnon arabicus (Burmeister) (Coleoptera: Scarabaeidae), in Tunisia, deduced from mitochondrial DNA sequences

Studies of insect vectors may be facilitated by using laboratory colonies. However, it has been suggested that the colony insects are not representative of natural populations, sometimes yealding to erroneous interpretations of the intraspecific genetic variation between the individuals. In the present study the variability of the mitochondrial gene cytochrome b was evaluated among a closed laboratory colony of Anopheles albimanus that was founded 20 years ago and the field population from which it was derived. The analyses revealed the presence of five and three nucleotide haplotypes in the wild and colony populations, respectively. Wild individuals presented greater variability than those of the colony based on the number of polymorphic sites, haplotype diversity, nucleotide diversity and mean values of nucleotide differences. The mean and net numbers of nucleotide substitutions per site between populations and the significant F ST value calculated (0,37179, P = 0.05) indicate that there is a considerable degree of genetic differentiation between them. The phylogenetic tree showed that the colony haplotypes appear to be derived from the wild population. These results suggest a great genetic variability in wild specimens compared with the laboratory ones as a consequence of a long time of colonization.

/pdf/mitochondrial-dna-divergence-between-wild-and-laboratory-2psw1vdztl.pdf

Mitochondrial DNA divergence between wild and laboratory populations of Anopheles albimanus Wiedemann (Diptera: Culicidae)

In this study bioremediation is presented as an alternative for the recovery of contaminated ecosystems. In this work an experimental diesel spill on pastureland was remediated using two bioremediation technologies: natural attenuation, which is the natural capability of indigenous microorganisms to degrade a xenobiotic component in a determined time, and biostimulation, which consist in the acceleration of the degradation process through the stimulation of the metabolism of indigenous microorganisms by the addition of nutrients (P and N) to the media. Results of respirometry assays indicated that both treatments produced significant levels of hydrocarbon removal but the biostimulation treatment stranded out with 98.17% degradation. Seven bacterial isolates were obtained from these treatments which according to their molecular characterization and phylogenetic analysis belong to the genus: Enterobacter, Bacillus, Arthrobacter, Sanguibacter, Staphylococcus and Flavobacterium. All isolates were able to metabolize diesel as a carbon and energy source; for this reason and taking into account that for some of these microorganisms their role in bioremediation have not been extensively studied, it is recommended to continue with their evaluation to know their real potential for the solution of environmental problems.

Caracterización fenotipica y molecular de poblaciones bacterianas aisladas de un suelo contaminado

En este estudio se presenta la biorremediacion como alternativa para la recuperacion de ecosistemas contaminados. En este trabajo se realizo un derrame experimental de diesel sobre un suelo de pastoreo, el cual fue remediado haciendo uso de dos tecnologias de biorremediacion: atenuacion natural; conocida como la capacidad natural de los microorganismos nativos para degradar en un tiempo determinado cualquier compuesto xenobiotico, y bioestimulacion; conocida como la adicion al medio de nutrientes (fosforo y nitrogeno) con el fin de estimular el metabolismo de los microorganismos nativos, logrando con esto acelerar el proceso de degradacion. Los resultados de la prueba de respirometria indicaron que ambos tratamientos produjeron valores significativos de remocion del hidrocarburo pero el tratamiento de bioestimulacion se destaco con el 98,17% de degradacion. Se obtuvieron siete aislamientos bacterianos a partir de las siembras realizadas, segun la caracterizacion molecular pertenecen a los generos: Enterobacter, Bacillus, Arthrobacter, Sanguibacter, Staphylococcus y Flavobacterium. Todos los aislamientos fueron capaces de metabolizar el diesel como fuente de carbono y energia; por ello y teniendo en cuenta que para algunos de estos microorganismos su papel en biorremediacion no ha sido estudiado extensivamente, se recomienda continuar con su evaluacion para conocer cual es realmente su potencial para la solucion de problemas ambientales.

/pdf/caracterizacion-fenotipica-y-molecular-de-poblaciones-4772jqm8gw.pdf

Caracterización fenotipica y molecular de poblaciones bacterianas aisladas de un suelo contaminado con diesel y sometido a dos tecnologías de biorremediación

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Mitochondrial DNA divergence between wild and laboratory populations of Anopheles albimanus Wiedemann (Diptera: Culicidae)

Caracterización fenotipica y molecular de poblaciones bacterianas aisladas de un suelo contaminado

Caracterización fenotipica y molecular de poblaciones bacterianas aisladas de un suelo contaminado con diesel y sometido a dos tecnologías de biorremediación