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Separate Populations (separate + population)
Selected AbstractsDo male and female black-backed woodpeckers respond differently to gaps in habitat?EVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 3 2010Jennifer C. Pierson Abstract We used population- and individual-based genetic approaches to assess barriers to movement in black-backed woodpeckers (Picoides arcticus), a fire-specialist that mainly occupies the boreal forest in North America. We tested if male and female woodpeckers exhibited the same movement patterns using both spatially implicit and explicit genetic analyses to define population structure and movement patterns of both sexes among populations. Three genetic groups were identified, a large, genetically continuous population that spans from the Rocky Mountains to Quebec, a small isolated population in South Dakota and a separate population in the western portion of their distribution (Oregon). Patterns of genetic diversity suggest extensive gene flow mediated by both males and females within the continuous boreal forest. However, male-mediated gene flow is the main form of connectivity between the continuously distributed group and the smaller populations of South Dakota and Oregon that are separated by large areas of unforested habitat, which apparently serves as a barrier to movement of female woodpeckers. [source] Phylogeography of lions (Panthera leo ssp.) reveals three distinct taxa and a late Pleistocene reduction in genetic diversityMOLECULAR ECOLOGY, Issue 8 2009ROSS BARNETT Abstract Lions were the most widespread carnivores in the late Pleistocene, ranging from southern Africa to the southern USA, but little is known about the evolutionary relationships among these Pleistocene populations or the dynamics that led to their extinction. Using ancient DNA techniques, we obtained mitochondrial sequences from 52 individuals sampled across the present and former range of lions. Phylogenetic analysis revealed three distinct clusters: (i) modern lions, Panthera leo; (ii) extinct Pleistocene cave lions, which formed a homogeneous population extending from Europe across Beringia (Siberia, Alaska and western Canada); and (iii) extinct American lions, which formed a separate population south of the Pleistocene ice sheets. The American lion appears to have become genetically isolated around 340 000 years ago, despite the apparent lack of significant barriers to gene flow with Beringian populations through much of the late Pleistocene. We found potential evidence of a severe population bottleneck in the cave lion during the previous interstadial, sometime after 48 000 years, adding to evidence from bison, mammoths, horses and brown bears that megafaunal populations underwent major genetic alterations throughout the last interstadial, potentially presaging the processes involved in the subsequent end-Pleistocene mass extinctions. [source] Lack of evidence of stimulatory autoantibodies to platelet-derived growth factor receptor in patients with systemic sclerosisARTHRITIS & RHEUMATISM, Issue 4 2009Jean-François Classen Objective Systemic sclerosis (SSc) is a severe connective tissue disease of unknown etiology, characterized by fibrosis of the skin and multiple internal organs. Recent findings suggested that the disease is driven by stimulatory autoantibodies to platelet-derived growth factor receptor (PDGFR), which stimulate the production of reactive oxygen species (ROS) and collagen by fibroblasts. These results opened novel avenues of research into the diagnosis and treatment of SSc. The present study was undertaken to confirm the presence of anti-PDGFR antibodies in patients with SSc. Methods Immunoglobulins from 37 patients with SSc were purified by protein A/G chromatography. PDGFR activation was tested using 4 different sensitive bioassays, i.e., cell proliferation, ROS production, signal transduction, and receptor phosphorylation; the latter was also tested in a separate population of 7 patients with SSc from a different research center. Results Purified IgG samples from patients with SSc were positive when tested for antinuclear autoantibodies, but did not specifically activate PDGFR, or PDGFR, in any of the tests. Cell stimulation with PDGF itself consistently produced a strong signal. Conclusion The present results raise questions regarding the existence of agonistic autoantibodies to PDGFR in SSc. [source] Population structure and migratory directions of Scandinavian bluethroats Luscinia svecica, a molecular, morphological and stable isotope analysisECOGRAPHY, Issue 1 2008Olof Hellgren Many species of birds show evidence of secondary contact zones and subspeciation in their Scandinavian distribution range, presumably resulting from different post-glacial recolonization routes. We investigated whether this is the case also in the Scandinavian bluethroat Luscinia svecica, a species that has been suggested to consist of two separate populations: one SW-migrating and long-winged (L. s. gaetkei) breeding in southern Norway, and one shorter-winged ESE-migrating (L. s. svecica) in northern Scandinavia. We sampled males at eleven breeding sites from southern Norway to northernmost Sweden. There were no morphological differences or latitudinal trends within the sample, neither were there any genetic differences or latitudinal trends as measured by variation in AFLP and microsatellite markers. Stable isotope ratios of throat feathers moulted on the wintering grounds showed no, or possibly marginal differences between birds from southern Norway and northern Sweden. We also re-measured old museum skins that in previous studies were classified as L. s.gaetkei, and found marginally longer wings in birds from the southern part of the Scandinavian breeding range. The difference, however, was much smaller than proposed in earlier studies. We conclude that there is no evidence of a genetic population structure among Scandinavian bluethroats that would suggest the presence of a zone of secondary contact. Finally we discuss whether the presumed subspecies gaetkei ever existed. [source] Functional subdivision of feline spinal interneurons in reflex pathways from group Ib and II muscle afferents; an updateEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2010Elzbieta Jankowska Abstract A first step towards understanding the operation of a neural network is identification of the populations of neurons that contribute to it. Our aim here is to reassess the basis for subdivision of adult mammalian spinal interneurons that mediate reflex actions from tendon organs (group Ib afferents) and muscle spindle secondary endings (group II afferents) into separate populations. Re-examining the existing experimental data, we find no compelling reasons to consider intermediate zone interneurons with input from group Ib afferents to be distinct from those co-excited by group II afferents. Similar patterns of distributed input have been found in subpopulations that project ipsilaterally, contralaterally or bilaterally, and in both excitatory and inhibitory interneurons; differences in input from group I and II afferents to individual interneurons showed intra- rather than inter-population variation. Patterns of reflex actions evoked from group Ib and II afferents and task-dependent changes in these actions, e.g. during locomotion, may likewise be compatible with mediation by premotor interneurons integrating information from both group I and II afferents. Pathological changes after injuries of the central nervous system in humans and the lineage of different subclasses of embryonic interneurons may therefore be analyzed without need to consider subdivision of adult intermediate zone interneurons into subpopulations with group Ib or group II input. We propose renaming these neurons ,group I/II interneurons'. [source] Geographical variation in the size of body organs in seabirdsFUNCTIONAL ECOLOGY, Issue 3 2000G. M. Hilton Abstract 1.,The size of body organs shows adaptive temporal variation in many animal species. The variation in the size of body organs was examined to see if it is also a component of local adaptation to geographical variation in ecological conditions. 2.,Major body organs were measured in five species of Icelandic seabirds, sampled from two areas where birds experience slightly different ecological conditions. Between-area differences in ecological conditions were consistent among the study species, allowing tests of the generality of ecological effects on organ size. 3.,All major body organs showed geographical size variation. Livers and kidneys were larger in locations where daily energy expenditure was expected to be higher; small intestines were heavier where food was of lower energy density; stomachs were heavier where food was less digestible; heart and flight muscle were larger where flight costs were greater. 4.,It is concluded that adaptive variation in organ size may be an important means by which animals optimize exploitation of their local environment, and may be a proximate factor in intraspecific life-history and metabolic variations between geographically separate populations. [source] Evidence for selection on coloration in a Panamanian poison frog: a coalescent-based approachJOURNAL OF BIOGEOGRAPHY, Issue 5 2010Jason L. Brown Abstract Aim, The strawberry poison frog, Oophaga pumilio, has undergone a remarkable radiation of colour morphs in the Bocas del Toro archipelago in Panama. This species shows extreme variation in colour and pattern between populations that have been geographically isolated for < 10,000 years. While previous research has suggested the involvement of divergent selection, to date no quantitative test has examined this hypothesis. Location, Bocas del Toro archipelago, Panama. Methods, We use a combination of population genetics, phylogeography and phenotypic analyses to test for divergent selection in coloration in O. pumilio. Tissue samples of 88 individuals from 15 distinct populations were collected. Using these data, we developed a gene tree using the mitochondrial DNA (mtDNA) d-loop region. Using parameters derived from our mtDNA phylogeny, we predicted the coalescence of a hypothetical nuclear gene underlying coloration. We collected spectral reflectance and body size measurements on 94 individuals from four of the populations and performed a quantitative analysis of phenotypic divergence. Results, The mtDNA d-loop tree revealed considerable polyphyly across populations. Coalescent reconstructions of gene trees within population trees revealed incomplete genotypic sorting among populations. The quantitative analysis of phenotypic divergence revealed complete lineage sorting by colour, but not by body size: populations showed non-overlapping variation in spectral reflectance measures of body coloration, while variation in body size did not separate populations. Simulations of the coalescent using parameter values derived from our empirical analyses demonstrated that the level of sorting among populations seen in colour cannot reasonably be attributed to drift. Main conclusions, These results imply that divergence in colour, but not body size, is occurring at a faster rate than expected under neutral processes. Our study provides the first quantitative support for the claim that strong diversifying selection underlies colour variation in the strawberry poison frog. [source] Divergence with gene flow between Ponto-Caspian refugia in an anadromous cyprinid Rutilus frisii revealed by multiple gene phylogeographyMOLECULAR ECOLOGY, Issue 4 2008PETR KOTLÍK Abstract The Black and Caspian Seas have experienced alternating periods of isolation and interconnection over many Milankovitch climate oscillations and most recently became separated when the meltwater overflow from the Caspian Sea ceased at the end of the last glaciation. Climate-induced habitat changes have indisputably had profound impacts on distribution and demography of aquatic species, yet uncertainties remain about the relative roles of isolation and dispersal in the response of species shared between the Black and Caspian Sea basins. We examined these issues using phylogeographical analysis of an anadromous cyprinid fish Rutilus frisii. Bayesian coalescence analyses of sequence variation at two nuclear and one mitochondrial genes suggest that the Black and Caspian Seas supported separate populations of R. frisii during the last glaciation. Parameter estimates from the fitted isolation-with-migration model showed that their separation was not complete, however, and that the two populations continued to exchange genes in both directions. These analyses also suggested that majority of migrations occurred during the Pleistocene, showing that the variation shared between the Black and Caspian Seas is the result of ancient dispersal along the temporary natural connections between the basins, rather than of incomplete lineage sorting or recent human-mediated dispersal. Gene flow between the refugial populations was therefore an important source of genetic variation, and we suggest that it facilitated the evolutionary response of the populations to changing climate. [source] Low gene flow but high genetic diversity in the threatened Mallorcan midwife toad Alytes muletensisMOLECULAR ECOLOGY, Issue 11 2005F. J. L. KRAAIJEVELD-SMIT Abstract We investigated fine-scale genetic structuring in the rare and vulnerable Mallorcan midwife toad Alytes muletensis using eight polymorphic microsatellite markers. The current range of this amphibian is restricted to some 19 sites of which six are derived from reintroductions, all located in the mountain ranges of Mallorca. We sampled tadpoles from 14 pools covering 10 natural sites and two reintroduction sites for microsatellite DNA analyses. Relatively high levels of genetic variation were found in most pools (HE = 0.38,0.71, allelic richness = 2.6,6.2). Only at one pool has the population recently gone through a bottleneck. Dispersal between pools in different torrents does not occur whereas downstream dispersal between pools within the same torrent does happen at low frequencies. This occasional exchange of individuals does not lead to neighbouring pools in the same torrent being panmictic. This can be concluded because all FST values (0.12,0.53) differ significantly from zero and structure analyses identified neighbouring pools as separate populations. Furthermore, assignment and migration tests showed little exchange between neighbouring pools. If upstream locations or complete torrents go extinct, they are unlikely to be recolonized naturally. For conservation purposes, reintroductions of tadpoles to sites where local extinctions have occurred may therefore be advisable. [source] Lower oesophageal sphincter relaxation evoked by stimulation of the dorsal motor nucleus of the vagus in ferretsNEUROGASTROENTEROLOGY & MOTILITY, Issue 3 2002T. P. Abrahams Abstract, An understanding of the neural control of lower oesophageal sphincter (LOS) relaxation is clinically relevant because transient LOS relaxations (TLOSRs) are a mechanism of acid reflux into the oesophagus. Preganglionic motor neurones innervating the LOS are localized in the dorsal motor nucleus of the vagus (DMV). Based on a single study in cats, it is now widely accepted that these neurones are functionally organized into two separate populations, such that stimulation of the caudal and rostral DMV evokes LOS relaxation and contraction, respectively. Our goal was to map the functional LOS responses to chemical stimulation in the DMV and nucleus tractus solitarius (NTS) of ferrets, an animal model commonly used for conscious studies on TLOSRs, and to test whether DMV-evoked LOS relaxation is mediated through hexamethonium-sensitive vagal-inhibitory pathways to the LOS. We used miniaturized manometry with Dentsleeve to monitor LOS and oesophageal pressures in decerebrate unanaesthetized ferrets. LOS relaxation was evoked readily in response to gastric insufflation, which shows that the vago,vagal reflex was intact in this preparation. Microinjections of l -glutamate (12.5 nmol L,1in 25 nL) were made into the DMV from approximately ,,1.5 to +,2.0 mm relative to the obex. Microinjections into the caudal (, 1.5 to +,0.0 mm behind obex) and intermediate (+ 0.1 to +,1.0 mm rostral to obex) DMV both significantly decreased LOS pressure, and complete LOS relaxation was noted in 28/32 and 11/18 cases, respectively. LOS relaxation responses to DMV microinjection were highly reproducible and abolished by bilateral vagotomy or hexamethonium (15 mg kg,1intravenously). A nitric oxide synthase inhibitor (l -NAME 100 mg kg,1intramuscularly) significantly increased the time taken to reach the maximal response. Increases in LOS pressure (24 ± 4 mmHg; n = 3) were obtained only when stimulation sites were located equal to greater than 1.5 mm rostral to the obex. LOS relaxation (, 78 ± 10%; n = 6) was evoked by stimulation of the NTS but not immediately outside of the NTS (11 ± 27%; n = 5). We conclude that there is a very extensive population of ,inhibitory' motor neurones in the DMV that may account for the predominant vagal-inhibitory tone in ferrets. As NTS stimulation evokes LOS relaxation and the predominant response to DMV stimulation is also LOS relaxation, this vago,vagal reflex may involve an excitatory interneurone between the NTS and DMV vagal inhibitory output. [source] Comparison of Localization of the Neurokinin 1 Receptor and Nitric Oxide Synthase with Calbindin D Labelling in the Rat Spinal CordANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 3 2000M. Nazli Summary A comparison of the localization of the neurokinin 1 (NK1) receptor and nitric oxide synthase with calbindin D labelling in the lumbar spinal cord was carried out in the rat using immunocytochemistry. Considerable regional variations were observed. Application of the antibody to calbindin D resulted in dense staining in laminae I and II and light staining in the other laminae. Occasional scattered cells were seen in the deep laminae and in the lamina X, the ventral horn and the lateral spinal nucleus. The results indicate that neurones expressing calbindin D, NK1 receptor and NOS are three separate populations in the dorsal horn of the lumbar spinal cord. [source] Phenotypic evolution in high-elevation populations of western fence lizards (Sceloporus occidentalis) in the Sierra Nevada MountainsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2010ADAM D. LEACHÉ Adaptive divergence in response to variable habitats, climates, and altitude is often accentuated along elevation gradients. We investigate phenotypic evolution in body size and coloration in the western fence lizard (Sceloporus occidentalis Baird & Girard, 1852) across elevation gradients in Yosemite National Park, California, situated in the Sierra Nevada mountains of Western North America. High-elevation populations occurring above 2100 m a.s.l. are recognized as a separate subspecies (Sceloporus occidentalis taylori Camp, 1916), with a distinctive phenotype characterized by a large body size and extensive blue ventral pigmentation. We sampled S. occidentalis from across elevation gradients in Yosemite National Park, California, and collected phenotypic data (body size and ventral coloration measurements; 410 specimens) and mitochondrial DNA sequence data (complete NADH1 gene; 969 bp, 181 specimens) to infer phylogenetic relationships, and examine the genetic and phenotypic diversity among populations. Populations of S. occidentalis in Yosemite National Park follow Bergmann's rule and exhibit larger body sizes in colder, high-elevation environments. The high-elevation subspecies S. o. taylori is not monophyletic, and the mitochondrial DNA genealogy supports a model of convergent phenotypic evolution among high-elevation populations belonging to different river drainages. The hypothesis that separate populations of S. occidentalis expanded up river drainages after the recession of glaciers is supported by population demographic analyses, and suggest that Bergmann's clines can evolve rapidly along elevation gradients. The distinctive high-elevation phenotype that is attributable to S. o. taylori has evolved independently several times, and includes adaptive phenotypic changes associated with increases in body size and ventral coloration. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 630,641. [source] DIFFERENTIAL NEURAL CONTROL OF GLOMERULAR ULTRAFILTRATIONCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 5-6 2004Kate M Denton Summary 1.,The renal nerves constrict the renal vasculature, causing decreases in renal blood flow (RBF) and glomerular filtration rate (GFR). Whether renal haemodynamics are influenced by changes in renal nerve activity within the physiological range is a matter of debate. 2.,We have identified two morphologically distinct populations of nerves within the kidney, which are differentially distributed to the renal afferent and efferent arterioles. Type I nerves almost exclusively innervate the afferent arteriole whereas type II nerves are distributed equally on the afferent and efferent arterioles. We have also demonstrated that type II nerves are immunoreactive for neuropeptide Y, whereas type I nerves are not. 3.,This led us to hypothesize that, in the kidney, distinct populations of nerves innervate specific effector tissues and that these nerves may be selectively activated, setting the basis for the differential neural control of GFR. In physiological studies, we demonstrated that differential changes in glomerular capillary pressure occurred in response to graded reflex activation of the renal nerves, compatible with our hypothesis. 4.,Thus, sympathetic outflow may be capable of selectively increasing or decreasing glomerular capillary pressure and, hence, GFR by differentially activating separate populations of renal nerves. This has important implications for our understanding of the neural control of body fluid balance in health and disease. [source] | ||||||||||||||||||||||||||||