Search results for "evolutionary"

Black box of phage–bacterium interactions : exploring alternative phage infection strategies

2021

The canonical lytic–lysogenic binary has been challenged in recent years, as more evidence has emerged on alternative bacteriophage infection strategies. These infection modes are little studied, and yet they appear to be more abundant and ubiquitous in nature than previously recognized, and can play a significant role in the ecology and evolution of their bacterial hosts. In this review, we discuss the extent, causes and consequences of alternative phage lifestyles, and clarify conceptual and terminological confusion to facilitate research progress. We propose distinct definitions for the terms ‘pseudolysogeny’ and ‘productive or non-productive chronic infection’, and distinguish them from…

Selektionstheorie und Rassenbildung beim Menschen

1952

So far, the applications of the theory of selection to human race formation have primarily considered the selective quality of individual race characters which are preferred by classification. However only few physiologically important race characters have been found to have an evident selective advantage. It is the climate laws, however, that prompt the assumption that selection will take place according to differences of vitality and fertility under certain climatic conditions and that the visible race characters are but incidental effects of pleiotropic gene. It also appears that, in contrast to selection, mutability must be given more consideration to-day than before. For instance the e…

From foes to friends: Viral infections expand the limits of host phenotypic plasticity

2020

Phenotypic plasticity enables organisms to survive in the face of unpredictable environmental stress. Intimately related to the notion of phenotypic plasticity is the concept of the reaction norm that places phenotypic plasticity in the context of a genotype-specific response to environmental gradients. Whether reaction norms themselves evolve and which factors might affect their shape has been the object of intense debates among evolutionary biologists along the years. Since their discovery, viruses have been considered as pathogens. However, new viromic techniques and a shift in conceptual paradigms are showing that viruses are mostly non-pathogenic ubiquitous entities. Recent studies hav…

2021

Interactions between organisms and their environments are central to how biological diversity arises and how natural populations and ecosystems respond to environmental change. These interactions involve processes by which phenotypes are affected by or respond to external conditions (e.g., via phenotypic plasticity or natural selection) as well as processes by which organisms reciprocally interact with the environment (e.g., via eco-evolutionary feedbacks). Organism-environment interactions can be highly dynamic and operate on different hierarchical levels, from genes and phenotypes to populations, communities, and ecosystems. Therefore, the study of organism-environment interactions requir…

Genetic and morphological differentiation in Tephritis bardanae (Diptera: Tephritidae): evidence for host-race formation

2003

The fruit fly Tephritis bardanae infests flower heads of two burdock hosts, Arctium tomentosum and A. minus. Observations suggest host-associated mating and behavioural differences at oviposition indicating host-race status. Previously, flies from each host plant were found to differ slightly in allozyme allele frequencies, but these differences could as well be explained by geographical separation of host plants. In the present study, we explicitly test whether genetic and morphological variance among T. bardanae are explained best by host-plant association or by geographical location, and if this pattern is stable over a 10-year period. Populations of A. tomentosum flies differed signific…

Historia breve de las contribuciones evolucionistas a la Filosofía Biológica predarwinista: desde la Edad Media hasta Darwin

2010

ResumenEl artículo presenta una sucinta exposición de las principales aportaciones sobre Filosofía Biológica realizadas por diversos autores al desarrollo del pensamiento evolucionista, durante el período histórico transcurrido entre el medievo y la articulación de la teoría darwinista. En particular, expone las contribuciones de diversa índole realizadas por Andrés Vesalio, Andrew Battell, Jacobo Bondt, Nicolás Tulp, Edward Tyson, John Ray, Benoit de Maillet, Pierre Louis Moreau de Maupertuis, Karl von Linneo, Georges Louis Leclerc, Félix de Azara y Jean Baptiste Lamarck.Palabras claveHistoria de la ciencia, historia de la filosofía biológica, evolucionismo predarwinista, orígenes de la pr…

«Evo-devo meets the Mind». La questione dell’esperienza estetica e l’evoluzionismo contemporaneo, dall’ipotesi degli adattamenti modulari all’interpr…

2013

Is it achievable to read aesthetic experience as a modular adaptation, and what would be its implication on the image of man, on aesthetics and on evolutionary theory itself? An alternative path is offered by evolutionary morphology, starting from the elaboration of a biologic concept of organism and from the notion of homology of function as a system of interconnections organized in a hierarchy. We deduce the possibility of thinking the peculiar innovation of aesthetic experience in an evolutionary way.

Molecular phylogeny of the freshwater sponges in Lake Baikal

2003

The phylogenetic relationship of the freshwater sponges (Porifera) in Lake Baikal is not well understood. A polyphyletic and/or monophyletic origin have been proposed. The (endemic) Baikalian sponges have been subdivided into two families: endemic Lubomirskiidae and cosmopolitan Spongillidae. In the present study, two new approaches have been made to resolve the phylogenetic relationship of Baikalian sponges; analysis of (1) nucleotide sequences from one mitochondrial gene, the cytochrome oxidase subunit I (COI) and of (2) one selected intron from the tubulin gene. Specimens from the following endemic Baikalian sponge species have been studied; Lubomirskia baicalensis, Baikalospongia interm…

Ancient recruitment by chromists of green algal genes encoding enzymes for carotenoid biosynthesis.

2008

Chromist algae (stramenopiles, cryptophytes, and haptophytes) are major contributors to marine primary productivity. These eukaryotes acquired their plastid via secondary endosymbiosis, whereby an early-diverging red alga was engulfed by a protist and the plastid was retained and its associated nuclear-encoded genes were transferred to the host genome. Current data suggest, however, that chromists are paraphyletic; therefore, it remains unclear whether their plastids trace back to a single secondary endosymbiosis or, alternatively, this organelle has resulted from multiple independent events in the different chromist lineages. Both scenarios, however, predict that plastid-targeted, nucleus-…

The Phylogenetic position of Daubentonia madagascariensis (Gmelin, 1788; primates, Strepsirhini) as revealed by chromosomal analysis

2012

One of the major topics in primate evolution is the phylogenetic position of the bizarre Daubentonia madagascariensis (DMA, aye-aye). The principal points that have been discussed for many decades are whether the aye-aye is: (i) the sister group of primates; (ii) the sister group of strepsirhines; or (iii) the sister group of lemurs. Very little is known about Daubentonia evolution, particularly on the chromosomal background. The present report focuses on the chromosomal history of this species. We used available chromosome painting data as the main source to identify conserved chromosomes, chromosomal segments and syntenic associations that have characterized the aye-aye karyotype. The dat…