Plaza de postdoctorado en entomologia

Mensaje de: Javier Mota Sanchez, email

A los interesados en ocupar una plaza de postdoctorado en entomologia, por
un periodo de dos años (disponible a partir de Agosto, 2009) en el
departamento de Virologia e Inmunologia del Southwest Foundation for
Biomedical Research, favor de comunicarse con el Dr. Javier Mota Snchez al
correo electronico o al telfono (210) 290-8271 en San Antonio
Tx, USA.


Es deseable, pero no indispensable, que los interesados tengan experiencia
trabajando con Aedes aegypti y/o dengue.

Bigger is better: the largest phylogenetic tree reconstructed. | Archetype

Bigger is better: the largest phylogenetic tree reconstructed. | Archetype

Sunday, May 3rd, 2009 | Cladistics, Phylogeny, Uncategorized

GenBank, the standard database for genetic information maintained by National Center for Biotechnology Information, has been accumulating DNA sequences for some three decades now. Since its creation in the late 1980s, it has become the de facto repository for genetic information– genetic data must now be submitted to GenBank for a paper to be accepted for publication. Most sequence data accumulated is the result of the sum of many “local” taxonomic studies, that have targeted a particular group of organism for a relatively small, but well-known collection of genes. It contents now span over hundreds of genes across all of life’s domains. So, what would happen if you were to take all the sequence information contained in GenBank and analyze it phylogenetically all together in a single, one-step study? Well, that is what Pablo A. Goloboff and coworkers just did, the results of which were published in last week’s online early edition of Cladistics, the international journal of the Willi Hennig Society.

--------------

Lea el comentario completo en:

"Archetype, Ant reconstruction one homology at a time"

blog por Roberto Keller

Cladistics: Analisis de una matriz gigante de >73000 UT

Esto si que es difícil de creer: el análisis cladístico de una matriz "super gigante" de 73060 entidades. Así es, no es error de dedo, más de 73 mil unidades terminales! Este análisis portentoso fue efectuado por un equipo basado en Tucumán (Argentina) liderado por Pablo Goloboff. La referencia del artículo, por ahora solo disponible en linea, es:

Phylogenetic analysis of 73 060 taxa corroborates major eukaryotic groups
Pablo A. Goloboff, Santiago A. Catalano, J. Marcos Mirande, Claudia A. Szumik, J. Salvador Arias, Mari Källersjö and James S. Farris.
Cladistics
http://dx.doi.org/10.1111/j.1096-0031.2009.00255.x

ABSTRACT
Obtaining a well supported schema of phylogenetic relationships among the major groups of living organisms requires considering as much taxonomic diversity as possible, but the computational cost of calculating large phylogenies has so far been a major obstacle. We show here that the parsimony algorithms implemented in TNT can successfully process the largest phylogenetic data set ever analysed, consisting of molecular sequences and morphology for 73 060 eukaryotic taxa. The trees resulting from molecules alone display a high degree of congruence with the major taxonomic groups, with a small proportion of misplaced species; the combined data set retrieves these groups with even higher congruence. This shows that tree-calculation algorithms effectively retrieve phylogenetic history for very large data sets, and at the same time provides strong corroboration for the major eukaryotic lineages long recognized by taxonomists.

Antes de este logro, la idea de matriz "grande" andaba en los 500-1000 unidades terminales (Uts), y los más ambiciosos se esforzaban por ensamblar y analizar matrices de 1500 a 2000 unidades. Obviamente las dificultades para realizar análisis filogenéticos crecen desmesuradamente con cada unidad agregada a la matriz. Los intentos de exploración del enorme espacio de los arboles con estrategias y software convencional (como PAUP) no permitían ni siquiera ver la posibilidad de intentar el análisis de matrices gigantes. Entonces, Goloboff et al (2009) como lo lograron?
Ademas del trabajo tenaz y laborioso que implica compilar una matriz con tantas unidades terminales y caracteres moleculares y morfológicos, la clave del éxito fueron las capacidades analíticas de este grupo de investigadores usando el software TNT.

Bye bye Super-Trees, bienvenidas las SUPER-MATRICES!!!
-
Goloboff, P., Catalano, S., Marcos Mirande, J., Szumik, C., Salvador Arias, J., Källersjö, M., & Farris, J. (2009). Phylogenetic analysis of 73 060 taxa corroborates major eukaryotic groups Cladistics DOI: 10.1111/j.1096-0031.2009.00255.x
-