Search results for "evolutionary biology"
showing 10 items of 3886 documents
Gisekia(Gisekiaceae): Phylogenetic relationships, biogeography, and ecophysiology of a poorly known C4lineage in the Caryophyllales
2014
• Premise of the study: Gisekiaceae are a monogeneric family of the core Caryophyllales distributed in arid regions of Africa and Asia. The only widespread species of the genus, Gisekia pharnaceoides, performs C4 photosynthesis based on CO2 compensation point measurements. This study investigates the C4 syndrome and its evolution in Gisekia. The infrageneric relationships, distribution and bioclimatic preferences of Gisekia are also investigated.• Methods: Leaf gas exchange characteristics, activity of Rubisco and major C4 cycle enzymes, and ultrastructural characteristics of mesophyll and bundle sheath cells are studied for Gisekia pharnaceoides. δ13C values and leaf anatomy are analyzed f…
The age and evolution of sociality in Stegodyphus spiders: a molecular phylogenetic perspective
2006
Social, cooperative breeding behaviour is rare in spiders and generally characterized by inbreeding, skewed sex ratios and high rates of colony turnover, processes that when combined may reduce genetic variation and lower individual fitness quickly. On these grounds, social spider species have been suggested to be unstable in evolutionary time, and hence sociality a rare phenomenon in spiders. Based on a partial molecular phylogeny of the genus Stegodyphus , we address the hypothesis that social spiders in this genus are evolutionary transient. We estimate the age of the three social species, test whether they represent an ancestral or derived state and assess diversification relative to s…
Subunit sequences of the 4 x 6-mer hemocyanin from the golden orb-web spider, Nephila inaurata. Intramolecular evolution of the chelicerate hemocyani…
2003
The transport of oxygen in the hemolymph of many arthropod and mollusc species is mediated by large copper-proteins that are referred to as hemocyanins. Arthropod hemocyanins are composed of hexamers and oligomers of hexamers. Arachnid hemocyanins usually form 4 x 6-mers consisting of seven distinct subunit types (termed a-g), although in some spider taxa deviations from this standard scheme have been observed. Applying immunological and electrophoretic methods, six distinct hemocyanin subunits were identified in the red-legged golden orb-web spider Nephila inaurata madagascariensis (Araneae: Tetragnathidae). The complete cDNA sequences of six subunits were obtained that corresponded to a-,…
Determining the potential impacts of fire and different land uses on splash erosion in the margins of drylands
2021
Abstract This research aimed to estimate the splash erosion and its evolution during the first months in specific land uses after a forest fire. The study area was located in Congosto (North-West Spain), in the margins of Spanish drylands, after a wildfire occurred in May 2012, which burned 15.56 ha of scrubland and Pinus reforestation. Two different burned land uses were selected and compared to control areas: i) burned pine forest; and, scrublands. Rainfall intensity and the number, sizes and speed of raindrops were measured by an optical disdrometer and soil loss by funnels. Moreover, infiltration, soil moisture content, aggregate stability, water repellence, pH and organic matter were a…
Molecular Evolution of Defense Pathways in Sponges: Self–Self-recognition and Fight against the Nonself
2016
This article provides an overview of the immune system in poriferans at a tissue, cellular, and molecular level. Despite their simple organization, sponges have developed molecular mechanisms to recognize and resist foreign organisms. They are able to distinguish among food organisms, pathogens, and sponge-associated organisms. Although they lack specialized immune cells, sponges display molecular precursors, which are similar to molecular mediators involved in innate and adaptive immune systems, present in more evolutionarily advanced taxa, as outlined in succeeding articles in the Phylogeny section.
Metagenomics reveals our incomplete knowledge of global diversity
2008
Metagenomic sequencing obtains huge amounts of sequences from environmental and clinical samples, thus providing a glimpse of the global prokaryotic diversity of both species and genes in these sources. The current trend in metagenomic analysis follows the so-called gene-centric approach, focused on describing the environments by the study of the functional roles of the proteins encoded in the sequenced genes. In this way, it is clear that metagenomic analysis relies heavily on the accurate knowledge of the universe of proteins stored in the databases. Nevertheless, it is known that some biases exist in the composition of databases (which are rich in sequences from common, cultivable and ea…
RNA viruses as complex adaptive systems
2004
RNA viruses have high mutation rates and so their populations exist as dynamic and complex mutant distributions. It has been consistently observed that when challenged with a new environment, viral populations adapt following hyperbolic-like kinetics: adaptation is initially very rapid, but then slows down as fitness reaches an asymptotic value. These adaptive dynamics have been explained in terms of populations moving towards the top of peaks on rugged fitness landscapes. Fitness fluctuations of varying magnitude are observed during adaptation. Often the presence of fluctuations in the evolution of physical systems indicates some form of self-organization, or where many components of the s…
Ancestral processes in population genetics-the coalescent.
2000
A special stochastic process, called the coalescent, is of fundamental interest in population genetics. For a large class of population models this process is the appropriate tool to analyse the ancestral structure of a sample of n individuals or genes, if the total number of individuals in the population is sufficiently large. A corresponding convergence theorem was first proved by Kingman in 1982 for the Wright-Fisher model and the Moran model. Generalizations to a large class of exchangeable population models and to models with overlying mutation processes followed shortly later. One speaks of the "robustness of the coalescent, as this process appears in many models as the total populati…
The Structural Variety and Metabolism of Proteins
1994
Individual eukaryote cells contain in the order of 104 different proteins, and each animal species contains an even greater number due to differences between the tissues of an individual and between the individuals themselves; furthermore, the protein spectrum changes during the course of development. The number of different proteins to be found in extant organisms may be as high as 1012. The description of this variety, its origin and biological significance is the most extensive theme in comparative biochemistry. This chapter will concern itself with the possibilities for structural variation and the general metabolism of proteins; further chapters will deal with comparative studies of in…
Systematic position of Dinidoridae within the superfamily Pentatomoidea (Hemiptera: Heteroptera) revealed by the Bayesian phylogenetic analysis of th…
2012
Mitochondrial 12S and 16S rDNA sequences of five species of Dinidoridae Stål, 1868, a largely Paleotropical family, and 16 other shield bugs (Pentatomoidea) were studied. This was the first molecular examination of the systematic position of this family within the superfamily Pentatomoidea using more than a single dinidorid species. Phylogenetic trees obtained from the Bayesian inference of 12S and 16S sequences of these mitochondrial DNA, identified Dinidoridae as the monophylum and a sister group to the Tessaratomidae. Moreover, results of the study suggested a close molecular affinity of the genus Eumenotes to representatives of the subfamily Dinidorinae, which contradicts all previous m…