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Species Shows (species + shows)
Selected AbstractsGENE FLOW AND SPECIES DELIMITATION: A CASE STUDY OF TWO PINE SPECIES WITH OVERLAPPING DISTRIBUTIONS IN SOUTHEAST CHINAEVOLUTION, Issue 8 2010Yong Feng Zhou Species delimitation detected by molecular markers is complicated by introgression and incomplete lineage sorting between species. Recent modeling suggests that fixed genetic differences between species are highly related to rates of intraspecific gene flow. However, it remains unclear whether such differences are due to high levels of intraspecific gene flow overriding the spread of introgressed alleles or favoring rapid lineage sorting between species. In pines, chloroplast (cp) and mitochondrial (mt) DNAs are normally paternally and maternally inherited, respectively, and thus their relative rates of intraspecific gene flow are expected to be high and low, respectively. In this study, we used two pine species with overlapping geographical distributions in southeast China, P. massoniana and P. hwangshanensis, as a model system to examine the association between organelle gene flow and variation within and between species. We found that cpDNA variation across these two pine species is more species specific than mtDNA variation and almost delimits taxonomic boundaries. The shared mt/cp DNA genetic variation between species shows no bias in regard to parapatric versus allopatric species' distributions. Our results therefore support the hypothesis that high intraspecific gene flow has accelerated cpDNA lineage sorting between these two pine species. [source] Single amino acid repeats in signal peptidesFEBS JOURNAL, Issue 15 2010abaj There has been an increasing interest in single amino acid repeats ever since it was shown that these are the cause of a variety of diseases. Although a systematic study of single amino acid repeats is challenging, they have subsequently been implicated in a number of functional roles. In general surveys, leucine runs were among the most frequent. In the present study, we present a detailed investigation of repeats in signal peptides of secreted and type I membrane proteins in comparison with their mature parts. We focus on eukaryotic species because single amino acid repeats are generally rather rare in archaea and bacteria. Our analysis of over 100 species shows that repeats of leucine (but not of other hydrophobic amino acids) are over-represented in signal peptides. This trend is most pronounced in higher eukaryotes, particularly in mammals. In the human proteome, although less than one-fifth of all proteins have a signal peptide, approximately two-thirds of all leucine repeats are located in these transient regions. Signal peptides are cleaved early from the growing polypeptide chain and then degraded rapidly. This may explain why leucine repeats, which can be toxic, are tolerated at such high frequencies. The substantial fraction of proteins affected by the strong enrichment of repeats in these transient segments highlights the bias that they can introduce for systematic analyses of protein sequences. In contrast to a general lack of conservation of single amino acid repeats, leucine repeats were found to be more conserved than the remaining signal peptide regions, indicating that they may have an as yet unknown functional role. [source] Temperature affects longevity and age-related locomotor and cognitive decay in the short-lived fish Nothobranchius furzeriAGING CELL, Issue 3 2006Dario R. Valenzano Summary Temperature variations are known to modulate aging and life-history traits in poikilotherms as different as worms, flies and fish. In invertebrates, temperature affects lifespan by modulating the slope of age-dependent acceleration in death rate, which is thought to reflect the rate of age-related damage accumulation. Here, we studied the effects of temperature on aging kinetics, aging-related behavioural deficits, and age-associated histological markers of senescence in the short-lived fish Nothobranchius furzeri. This species shows a maximum captive lifespan of only 3 months, which is tied with acceleration in growth and expression of aging biomarkers. These biological peculiarities make it a very convenient animal model for testing the effects of experimental manipulations on life-history traits in vertebrates. Here, we show that (i) lowering temperature from 25 °C to 22 °C increases both median and maximum lifespan; (ii) life extension is due to reduction in the slope of the age-dependent acceleration in death rate; (iii) lowering temperature from 25 °C to 22 °C retards the onset of age-related locomotor and learning deficits; and (iv) lowering temperature from 25 °C to 22 °C reduces the accumulation of the age-related marker lipofuscin. We conclude that lowering water temperature is a simple experimental manipulation which retards the rate of age-related damage accumulation in this short-lived species. [source] Functional genital morphology of armored spiders (Arachnida: Araneae: Tetrablemmidae)JOURNAL OF MORPHOLOGY, Issue 9 2008Matthias BurgerArticle first published online: 18 JUN 200 Abstract This study describes the female genitalia of the tetrablemmid spiders Brignoliella acuminata, Monoblemma muchmorei, Caraimatta sbordonii, Tetrablemma magister, and Ablemma unicornis by means of serial semi-thin sections and scanning electron microscopy and compares the results with previous findings on Indicoblemma lannaianum. Furthermore, the male palps and chelicerae are briefly described. The general vulval organization of females is complex and shows similarities in all of the investigated species. The copulatory orifice is situated near the posterior margin of the pulmonary plate. The opening of the uterus externus lies between the pulmonary and the postgenital plate. Paired copulatory ducts lead to sac-like receptacula. Except for A. unicornis, the male emboli of all investigated species are elongated and thread-like. However, they are too short to reach the receptacula. Hence, the spermatozoa have to be deposited inside the copulatory ducts. The same situation was also found in I. lannaianum. Females of this species store sperm encapsulated in secretory balls in their receptacula. The secretion is produced by glands adjoining the receptacula. The presence of paired fertilization ducts and spermatozoa in the uterus internus suggested that fertilization takes place internally in I. lannaianum. Secretory balls in the receptacula are found in all of the investigated species in this study, showing that sperm are stored in the same way. The place of fertilization may also be identical since dark particles, presumably spermatozoa, are located in the uterus internus of all investigated species except for T. magister. However, fertilization ducts are only found in B. acuminata and M. muchmorei. A sclerotized central process with attached muscles is present in A. unicornis, M. muchmorei, C. sbordonii and T. magister. Only in A. unicornis does the central process show an internal lumen and hold spermatozoa. In the other species, it could be used to lock the uterus during copulation in order to prevent sperm from getting into it as suggested for certain oonopid species. The uterus externus of all investigated species shows a sclerotized dorsal fold with attached muscles, previously described as "inner vulval plate." Contractions of the muscles lead to a widening of the dorsal fold, thus creating enough space for the large oocytes to pass the narrow uterus externus. The males of all investigated species have apophyses on their chelicerae. At least in B. acuminata and A. unicornis, where females have paired grooves on the preanal plate, these apophyses allow males to grasp the female during copulation as described for I. lannaianum. © 2008 Wiley-Liss, Inc. [source] Triple Dumbbell Polymer Nanolayer Frequency ResponseMACROMOLECULAR THEORY AND SIMULATIONS, Issue 6 2008Steven Grisafi Abstract A triple dumbbell sandwich model is developed to predict the frequency response of an interface created within nanolayer polymer films. One dumbbell different from two others is layered between the other two. The interactions among the macromolecules are modeled using Hooke's law for the intramolecular, intermolecular, and an applied external force. The external force is meant to describe incident electromagnetic radiation. The transient response of the system in the frequency domain is presented along with the steady-state response. The frequency response for the central dumbbell differs from its two partners suggesting that birefringence of incident radiation is possible. The phase angle of the oscillations for the two different polymer species shows that the frequency of incident light would be shifted differently by the two when it traverses the polymer film. [source] New Zealand phylogeography: evolution on a small continentMOLECULAR ECOLOGY, Issue 17 2009GRAHAM P. WALLIS Abstract New Zealand has long been a conundrum to biogeographers, possessing as it does geophysical and biotic features characteristic of both an island and a continent. This schism is reflected in provocative debate among dispersalist, vicariance biogeographic and panbiogeographic schools. A strong history in biogeography has spawned many hypotheses, which have begun to be addressed by a flood of molecular analyses. The time is now ripe to synthesize these findings on a background of geological and ecological knowledge. It has become increasingly apparent that most of the biota of New Zealand has links with other southern lands (particularly Australia) that are much more recent than the breakup of Gondwana. A compilation of molecular phylogenetic analyses of ca 100 plant and animal groups reveals that only 10% of these are even plausibly of archaic origin dating to the vicariant splitting of Zealandia from Gondwana. Effects of lineage extinction and lack of good calibrations in many cases strongly suggest that the actual proportion is even lower, in keeping with extensive Oligocene inundation of Zealandia. A wide compilation of papers covering phylogeographic structuring of terrestrial, freshwater and marine species shows some patterns emerging. These include: east,west splits across the Southern Alps, east,west splits across North Island, north,south splits across South Island, star phylogenies of southern mountain isolates, spread from northern, central and southern areas of high endemism, and recent recolonization (postvolcanic and anthropogenic). Excepting the last of these, most of these patterns seem to date to late Pliocene, coinciding with the rapid uplift of the Southern Alps. The diversity of New Zealand geological processes (sinking, uplift, tilting, sea level change, erosion, volcanism, glaciation) has produced numerous patterns, making generalizations difficult. Many species maintain pre-Pleistocene lineages, with phylogeographic structuring more similar to the Mediterranean region than northern Europe. This structure reflects the fact that glaciation was far from ubiquitous, despite the topography. Intriguingly, then, origins of the flora and fauna are island-like, whereas phylogeographic structure often reflects continental geological processes. [source] The nature of collision-induced dissociation processes of doubly protonated peptides: comparative study for the future use of matrix-assisted laser desorption/ionization on a hybrid quadrupole time-of-flight mass spectrometer in proteomicsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2001R. Cramer Comparative MS/MS studies of singly and doubly charged electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) precursor peptide ions are described. The spectra from these experiments have been evaluated with particular emphasis on the data quality for subsequent data processing and protein/amino acid sequence identification. It is shown that, once peptide ions are formed by ESI or MALDI, their charge state, as well as the collision energy, is the main parameter determining the quality of collision-induced dissociation (CID) MS/MS fragmentation spectra of a given peptide. CID-MS/MS spectra of singly charged peptides obtained on a hybrid quadrupole orthogonal time-of-flight mass spectrometer resemble very closely spectra obtained by matrix-assisted laser desorption/ionization post-source decay time-of-flight mass spectrometry (MALDI-PSD-TOFMS). On the other hand, comparison of CID-MS/MS spectra of either singly or doubly charged ion species shows no dependence on whether ions have been formed by ESI or MALDI. This observation confirms that, at the time of precursor ion selection, further mass analysis is effectively decoupled from the desorption/ionization event. Since MALDI ions are predominantly formed as singly charged species and ESI ions as doubly charged, the associated difference in the spectral quality of MS/MS spectra as described here imposes direct consequences on data processing, database searching using ion fragmentation data, and de novo sequencing when ionization techniques are changed. Copyright © 2001 John Wiley & Sons, Ltd. [source] Effect of dietary protein and energy levels on growth, oxygen consumption, haemolymph and digestive gland carbohydrates, nitrogen excretion and osmotic pressure of Litopenaeus vannamei (Boone) and L. setiferus (Linne) juveniles (Crustacea, Decapoda; Penaeidae)AQUACULTURE RESEARCH, Issue 7 2001C Rosas Abstract The influence of protein and energy levels on growth rate, survival, pre- and post-prandial oxygen consumption, ammonia excretion, haemolymph glucose (HG), glycogen in digestive gland and osmotic pressure (OP) in white shrimp Litopenaeus vannamei (Boone) and L. setiferus (Linne) juveniles was studied. Diets containing a high-quality protein at a protein/energy (P/E) ratio of 16, 26, 31 and 36 mg kJ,1 were fed at 20% of shrimp body weight of two sizes: < 1 g and >,1 g. Both species showed a optimum P/E ratio of 36 mg kJ,1 (33,44% protein and 6,23% carbohydrate) in juveniles <,1 g. For shrimp >,1 g, L. setiferus showed a higher growth rate in the diet with 16 mg kJ,1 (27% protein; 32% carbohydrate) and L. vannamei between 26 and 36 mg kJ,1 (33,44% protein and 6,23% carbohydrate). In both experiments, the growth rate of L. vannamei was 2,3 times that observed in L. setiferus. Routine oxygen consumption and apparent heat increment (AHI) of L. setiferus juveniles was two times higher than that observed in L. vannamei juveniles, which could indicate that L. setiferus has a higher metabolic rate. The O/N ratio varied according to protein level, with higher values (O/N = 180) with a 16-mg kJ,1 diet and lower values (O/N = 73) with a 36-mg kJ,1 diet in L. setiferus juveniles. A similar variation in O/N ratio was obtained in L. vannamei fed with all diets with an interval between 22 and 50. An inverse relation between ammonia excretion and HG, and digestive gland glycogen (DGG) in relation to an increase in the P/E ratio indicate that both shrimp species are well adapted to use carbohydrates and/or proteins from their diet. The higher values of hyper-osmotic capacity (hyper-OC) were observed in L. setiferus <,1 g fed with 36 mg kJ,1 and the lowest in L. vannamei <,1 g fed with 31 mg kJ,1. Intermediate values of hyper-OC were observed in both species fed all diets indicating that osmotic factors of juveniles <,1 g of both species are more affected by the P/E ratio than juveniles >,1 g. All results showed that juveniles >,1 g of both species are less dependent of P/E ratio than juveniles <,1 g. Litopenaeus vannamei is a most tolerant shrimp species with a high capacity to use a wide range of dietary P/E ratios for growth, which may be due to its lower energy requirements. Litopenaeus setiferus showed a lower capacity to accept different P/E ratios but the optimum P/E ratio obtained with this species shows that L. setiferus accept diets with a high carbohydrate level as well. These results demonstrate that there are nutritional and physiological differences that explain the differences that have been observed when both species were cultured in commercial ponds. [source] Population divergence in the amphicarpic species Amphicarpaea edgeworthii Benth. (Fabaceae): microsatellite markers and leaf morphologyBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2009ZHONG-CHENG LIANG Comparative analyses of the genetic differentiation in microsatellite markers (FST) and leaf morphology characters (QST) of Amphicarpaea edgeworthii Benth. were conducted to gain insight into the roles of random processes and natural selection in the population divergence. Simple sequence repeat analyses on 498 individuals of 19 natural populations demonstrate that a significant genetic differentiation occurs among populations (mean FST = 0.578), and A. edgeworthii is a highly self-fertilized species (mean selfing rate s = 0.989). The distribution pattern of genetic diversity in this species shows that central populations possess high genetic diversity (e.g. population WL with HE = 0.673 and population JG with HE = 0.663), whereas peripheral ones have a low HE as in population JD (0.011). The morphological divergence of leaf shape was estimated by the elliptical Fourier analysis on the data from 11 natural and four common garden populations. Leaf morphology analyses indicate the morphological divergence does not show strong correlation with the genetic differentiation (R = 0.260, P = 0.069). By comparing the 95% confidence interval of QST with that of FST, QST values for five out of 12 quantitative traits are significantly higher than the average FST value over eight microsatellite loci. The comparison of FST and QST suggests that two kinds of traits can be driven by different evolutionary forces, and the population divergence in leaf morphology is shaped by local selections. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 505,516. [source] | |||||||||||||