Doval, Daniel Heredia


La Biología Evolutiva es una disciplina central dentro de la Biología, dando coherencia y conexión a las ramas del estudio de la vida. Asociada casi invariablemente a la teoría sintética o síntesis neodarwinista, el estudio de la evolución se centra en fenómenos competitivos y procesos de variación poblacional de secuencias génicas bajo la influencia constante de la selección natural. No obstante, la importancia creciente, en representación y transcendencia, de fenómenos considerados tradicionalmente excepcionales (como la simbiosis, la transferencia horizontal y la actividad de elementos móviles), pueden ser de gran relevancia para la concepción general de la biología evolutiva, siendo necesario un enfoque que los sitúe como elementos centrales de la evolución y no como meras excepciones, en torno a un modelo más holístico de la naturaleza.

Universidad Autónoma de Madrid

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Michael Kackenberg

Dinámica evolutiva de los retrotransposones ALU en el genoma humano

Universidad de Granada, Departamento de Genética.

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Laurent Nottale, Jean Chaline, Pierre Grou

On the fractal structure of evolutionary trees

Summary. We analyse in terms of a fractal tree the time sequences of major evolutionary leaps at various scales : from the scale of the "global" tree of life (appearance of life to homeothermy), to the distinct scales of organization of clades, such as sauropod and theropod dinosaurs, North American equids, rodents, primates including hominids, and echinoderms. We also apply this type of model to the acceleration observed in the economic crisis / no-crisis pattern in Western and pre-Columbian civilizations. In each case we find that these data are consistent with a log-periodic law of acceleration or deceleration, to a high level of statistical significance. Such a law is characterized by a critical epoch of convergence Tc specific to the lineage under consideration. These results support a description of evolutionary trees in terms of critical phenomena.

1) DAEC (UMR CNRS 8631), Observatoire de Paris, 92195 Meudon Cedex, France.
2) BIOGEOSCIENCES (UMR CNRS 5561), EPHE, Université de Bourgogne, 6 Bd. Gabriel, 21000 Dijon, France.
3) Université de Versailles-Saint-Quentin, 47 Bd. Vauban, 78280 Guyancourt, France

Lynn Margulis

Una revolución en la evolución
Escritos seleccionados por el Departamento de Bioquímica y Biología molecular de la Universidad de Valencia.

Sección de ciencias biológicas. Instituto de Estudios Catalanes.

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Mark A. Ragan

Lateral transfer of genes and gene fragments in prokaryotes


Lateral genetic transfer (LGT) involves the movement of genetic material from one lineage into another, and its subsequent incorporation into the new host genome via genetic recombination. Studies in individual taxa have indicated lateral origins for stretches of DNA of greatly varying length, from a few nucleotides to chromosome size.

Here we analyse 1462 sets of single-copy, putatively orthologous genes from 144 fully sequenced prokaryote genomes, asking to what extent complete genes and fragments of genes have been transferred and recombined in LGT. Using a rigorous phylogenetic approach, we find evidence for LGT in at least 476 (32.6%) of these 1462 gene sets: 286 (19.6%) clearly show one or more observable recombination breakpoints within the boundaries of the open reading frame, while a further 190 (13.0%) yield trees that are topologically incongruent with the reference tree but do not contain a recombination breakpoint within the open reading frame. We refer to these gene sets as observable recombination breakpoint positive (ORB+) and negative (ORB-) respectively. The latter are prima facie instances of lateral transfer of an entire gene or beyond. We observe little functional bias between ORB+ and ORB- gene sets, but find that incorporation of entire genes is potentially more frequent in pathogens than in non-pathogens. As ORB+ gene sets are almost twice as common as ORB- sets in our data, the transfer of gene fragments has been relatively frequent, and the frequency of LGT may have been systematically underestimated in phylogenetic studies.

Cheong Xin Chan1,3, Robert G. Beiko1,2, Aaron E. Darling1,4 and Mark A. Ragan1*
1The University of Queensland, Institute for Molecular Bioscience and ARC Centre of
Excellence in Bioinformatics, Brisbane, Queensland 4072, Australia
2Dalhousie University, Department of Computer Science, 6050 University Avenue,
Halifax, Nova Scotia, Canada B3H 1W5
3Present address: Rutgers University, Department of Ecology, Evolution, and Natural
Resources, New Brunswick, NJ 08901, USA
4Present address: University of California Davis, Genome Center, Davis, CA 95616,

*Author for Correspondence: Mark Ragan, The University of Queensland, Institute for
Molecular Bioscience, Brisbane, Queensland 4072, Australia, tel +61-7-3346-2616, fax

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