Home About us Contact
|
Home About us Contact | ||
|
|
||
Range Changes (range + change)
Selected AbstractsDoppler ultrasound assessment of posterior tibial artery size in humansJOURNAL OF CLINICAL ULTRASOUND, Issue 5 2006Manning J. Sabatier PhD Abstract Purpose. The difference between structural remodeling and changes in tone of peripheral arteries in the lower extremities has not been evaluated. The purpose of this study was to (1) evaluate the day-to-day reproducibility and interobserver reliability (IOR) of posterior tibial artery (PTA) diameter measurements and (2) evaluate the effect of posture on PTA diameter at rest (Drest), during 10 minutes of proximal cuff occlusion (Dmin), and after the release of cuff occlusion (Dmax), as well as range (Dmax , Dmin) and constriction [(Dmax , Drest)/(Dmax , Dmin) × 100] in vivo. Methods. We used B-mode sonography to image the PTA during each condition. Results. Day-to-day reliability was good for Drest (intraclass correlation coefficient [ICC] 0.95; mean difference 4.2%), Dmin (ICC 0.93; mean difference 5.4%), and Dmax (ICC 0.99; mean difference 2.2%). The coefficient of repeatability for IOR was 70.5 ,m, with a mean interobserver error of 4.7 ,m. The seated position decreased Drest (2.6 ± 0.2 to 2.4 ± 0.3 mm; p = 0.002), increased Dmin (2.1 ± 0.2 to 2.4 ± 0.2 mm; p = 0.001), and decreased Dmax (3.1 ± 0.4 to 2.8 ± 0.3 mm; p < 0.001) compared with the supine position. The seated position also decreased arterial range (Dmax , Dmin) from 0.9 ± 0.2 to 0.5 ± 0.1 mm (p = 0.003) and increased basal arterial constriction from 57 ± 19% to 105 ± 27% (p = 0.007). Conclusions. The system employed for measuring PTA diameter yields unbiased and consistent estimates. Furthermore, lower extremity arterial constriction and range change with posture in a manner consistent with known changes in autonomic activity. © 2006 Wiley Periodicals, Inc. J Clin Ultrasound 34:223,230, 2006 [source] THE PHYLOGENETIC PATTERN OF SPECIATION AND WING PATTERN CHANGE IN NEOTROPICAL ITHOMIA BUTTERFLIES (LEPIDOPTERA: NYMPHALIDAE)EVOLUTION, Issue 7 2006Chris D. Jiggins Abstract Species level phylogenetic hypotheses can be used to explore patterns of divergence and speciation. In the tropics, speciation is commonly attributed to either vicariance, perhaps within climate-induced forest refugia, or ecological speciation caused by niche adaptation. Mimetic butterflies have been used to identify forest refugia as well as in studies of ecological speciation, so they are ideal for discriminating between these two models. The genus Ithomia contains 24 species of warningly colored mimetic butterflies found in South and Central America, and here we use a phylogenetic hypothesis based on seven genes for 23 species to investigate speciation in this group. The history of wing color pattern evolution in the genus was reconstructed using both parsimony and likelihood. The ancestral pattern for the group was almost certainly a transparent butterfly, and there is strong evidence for convergent evolution due to mimicry. A punctuationist model of pattern evolution was a significantly better fit to the data than a gradualist model, demonstrating that pattern changes above the species level were associated with cladogenesis and supporting a model of ecological speciation driven by mimicry adaptation. However, there was only one case of sister species unambiguously differing in pattern, suggesting that some recent speciation events have occurred without pattern shifts. The pattern of geographic overlap between clades over time shows that closely related species are mostly sympatric or, in one case, parapatric. This is consistent with modes of speciation with ongoing gene flow, although rapid range changes following allopatric speciation could give a similar pattern. Patterns of lineage accumulation through time differed significantly from that expected at random, and show that most of the extant species were present by the beginning of the Pleistocene at the latest. Hence Pleistocene refugia are unlikely to have played a major role in Ithomia diversification. [source] Geodetic imaging: reservoir monitoring using satellite interferometryGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2002D. W. Vasco Summary Fluid fluxes within subsurface reservoirs give rise to surface displacements, particularly over periods of a year or more. Observations of such deformation provide a powerful tool for mapping fluid migration within the Earth, providing new insights into reservoir dynamics. In this paper we use Interferometric Synthetic Aperture Radar (InSAR) range changes to infer subsurface fluid volume strain at the Coso geothermal field. Furthermore, we conduct a complete model assessment, using an iterative approach to compute model parameter resolution and covariance matrices. The method is a generalization of a Lanczos-based technique which allows us to include fairly general regularization, such as roughness penalties. We find that we can resolve quite detailed lateral variations in volume strain both within the reservoir depth range (0.4,2.5 km) and below the geothermal production zone (2.5,5.0 km). The fractional volume change in all three layers of the model exceeds the estimated model parameter uncertainty by a factor of two or more. In the reservoir depth interval (0.4,2.5 km), the predominant volume change is associated with northerly and westerly oriented faults and their intersections. However, below the geothermal production zone proper [the depth range 2.5,5.0 km], there is the suggestion that both north- and northeast-trending faults may act as conduits for fluid flow. [source] Use and misuse of the IUCN Red List Criteria in projecting climate change impacts on biodiversityGLOBAL CHANGE BIOLOGY, Issue 11 2006H. RESIT AKÇAKAYA Abstract Recent attempts at projecting climate change impacts on biodiversity have used the IUCN Red List Criteria to obtain estimates of extinction rates based on projected range shifts. In these studies, the Criteria are often misapplied, potentially introducing substantial bias and uncertainty. These misapplications include arbitrary changes to temporal and spatial scales; confusion of the spatial variables; and assume a linear relationship between abundance and range area. Using the IUCN Red List Criteria to identify which species are threatened by climate change presents special problems and uncertainties, especially for shorter-lived species. Responses of most species to future climate change are not understood well enough to estimate extinction risks based solely on climate change scenarios and projections of shifts and/or reductions in range areas. One way to further such understanding would be to analyze the interactions among habitat shifts, landscape structure and demography for a number of species, using a combination of models. Evaluating the patterns in the results might allow the development of guidelines for assigning species to threat categories, based on a combination of life history parameters, characteristics of the landscapes in which they live, and projected range changes. [source] Reconstructing the demise of Tethyan plants: climate-driven range dynamics of Laurus since the PlioceneGLOBAL ECOLOGY, Issue 6 2008Francisco Rodríguez-Sánchez ABSTRACT Aim Climate changes are thought to be responsible for the retreat and eventual extinction of subtropical lauroid species that covered much of Europe and North Africa during the Palaeogene and early Neogene; little is known, however, of the spatial and temporal patterns of this demise. Herein we calibrate ecological niche models to assess the climatic requirements of Laurus L. (Lauraceae), an emblematic relic from the Tethyan subtropical flora, subsequently using these models to infer how the range dynamics of Laurus were affected by Plio-Pleistocene climate changes. We also provide predictions of likely range changes resulting from future climatic scenarios. Location The Mediterranean Basin and Macaronesian islands (Canaries, Madeira, Azores). Methods We used a maximum-entropy algorithm (Maxent) to model the relationship between climate and Laurus distribution over time. The models were fitted both to the present and to the middle Pliocene, based on fossil records. We employed climatic reconstructions for the mid-Pliocene (3 Ma), the Last Glacial Maximum (21 ka) and a CO2 -doubling future scenario to project putative species distribution in each period. We validated the model projections with Laurus fossil and present occurrences. Results Laurus preferentially occupied warm and moist areas with low seasonality, showing a marked stasis of its climatic niche. Models fitted to Pliocene conditions successfully predicted the current species distribution. Large suitable areas existed during the Pliocene, which were strongly reduced during the Pleistocene, but humid refugia within the Mediterranean Basin and Macaronesian islands enabled long-term persistence. Future climate conditions are likely to re-open areas suitable for colonization north of the current range. Main conclusions The climatic requirements of Laurus remained virtually unchanged over the last 3 Myr. This marked niche conservatism imposed largely deterministic range dynamics driven by climate conditions. This species's relatively high drought tolerance might account for the survival of Laurus in continental Europe throughout the Quaternary whilst other Lauraceae became extinct. Climatic scenarios for the end of this century would favour an expansion of the species's range towards northern latitudes, while severely limiting southern populations due to increased water stress. [source] After the deluge: mitochondrial DNA indicates Miocene radiation and Pliocene adaptation of tree and giant weta (Orthoptera: Anostostomatidae)JOURNAL OF BIOGEOGRAPHY, Issue 2 2005Steven A. Trewick Abstract Aim, New Zealand broke away from the margins of Gondwana c. 75 Ma. Since then, New Zealand taxa derived from the Gondwanan biota are thought to have been exposed first to a subtropical climate on a low lying terrain, then severe land reduction during the Oligocene marine transgression, followed by much cooler climates of the Pliocene and Pleistocene, at which time mountain ranges emerged. The biological consequence of New Zealand's geological and climatic history is not well understood, in particular the extent to which the Oligocene acted as a biological bottleneck remains unresolved. Methods, We used mitochondrial cytochrome oxidase I and 12S DNA sequences to examine the extent of diversity and inferred timing of speciation of New Zealand weta (Anostostomatidae), a group of Orthoptera with a Gondwanan distribution generally thought to be ancient inhabitants of New Zealand. Main conclusions, We hypothesize that at least three distinct groups of weta survived the Oligocene marine transgression and radiated subsequently. Speciation followed during the Miocene and radiation into new habitats occurred during the Pliocene when mountain building created novel environments. Patterns of genetic diversity within species reflect, in some instances, geographical subdivision in the Pliocene, and in other cases, Pleistocene range changes resulting from climate change. [source] Climate change and the outbreak ranges of two North American bark beetlesAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 2 2002David W. Williams Abstract 1,One expected effect of global climate change on insect populations is a shift in geographical distributions toward higher latitudes and higher elevations. Southern pine beetle Dendroctonus frontalis and mountain pine beetle Dendroctonus ponderosae undergo regional outbreaks that result in large-scale disturbances to pine forests in the south-eastern and western United States, respectively. 2,Our objective was to investigate potential range shifts under climate change of outbreak areas for both bark beetle species and the areas of occurrence of the forest types susceptible to them. 3,To project range changes, we used discriminant function models that incorporated climatic variables. Models to project bark beetle ranges employed changed forest distributions as well as changes in climatic variables. 4,Projected outbreak areas for southern pine beetle increased with higher temperatures and generally shifted northward, as did the distributions of the southern pine forests. 5,Projected outbreak areas for mountain pine beetle decreased with increasing temperature and shifted toward higher elevation. That trend was mirrored in the projected distributions of pine forests in the region of the western U.S. encompassed by the study. 6,Projected outbreak areas for the two bark beetle species and the area of occurrence of western pine forests increased with more precipitation and decreased with less precipitation, whereas the area of occurrence of southern pine forests decreased slightly with increasing precipitation. 7,Predicted shifts of outbreak ranges for both bark beetle species followed general expectations for the effects of global climate change and reflected the underlying long-term distributional shifts of their host forests. [source] Phylogeography of sexual Heteronotia binoei (Gekkonidae) in the Australian arid zone: climatic cycling and repetitive hybridizationMOLECULAR ECOLOGY, Issue 9 2005JARED L. STRASBURG Abstract The biota of much of continental Australia have evolved within the context of gradual aridification of the region over several million years, and more recently of climatic cycling between relatively dry and humid conditions. We performed a phylogeographical study of three sexual chromosome races of the Heteronotia binoei complex of geckos found throughout the Australian arid zone. Two of these three races were involved in two separate hybridization events leading to parthenogenetic lineages (also H. binoei), and the third is widespread and broadly sympatric with the parthenogens. Based on our analyses, the three sexual races diversified approximately 6 million years ago in eastern Australia, during a period of aridification, then each moved west through northern, southern, and central dispersal corridors to occupy their current ranges. In each case, the timing of major phylogeographical inferences corresponds to inferred palaeoclimatic changes in continental Australia. This scenario provides a simple explanation for diversification, secondary contact, and hybridization between the races. However, data presented elsewhere indicate that formation of the parthenogens was considerably more recent than the westward expansion of the hybridizing races, and that multiple hybridization events were geographically and temporally distinct. We suggest that cyclical climate changes may have led to regional range changes that facilitated hybridization between the races, which are not currently known to be in sympatry. [source] Biogeography meets conservation: the genetic structure of the endangered lycaenid butterfly Lycaena helle (Denis & Schiffermüller, 1775)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2010JAN CHRISTIAN HABEL Cold-adapted species are thought to have had their largest distribution ranges in central Europe during the glacial periods. Postglacial warming caused severe range shifts of such taxa into higher latitudes and altitudes. We selected the boreomontane butterfly Lycaena helle (Denis & Schiffermüller, 1775) as an example to demonstrate the genetic effects of range changes, and to document the recent status of highly fragmented remnant populations. We analysed five polymorphic microsatellite loci in 1059 individuals sampled at 50 different localities scattered over the European distribution area of the species. Genetic differentiation was strong among the mountain ranges of western Europe, but we did not detect similarly distinct genetic groups following a geographical pattern in the more eastern areas. The Fennoscandian populations form a separate genetic group, and provide evidence for a colonization from southern Finland via northern Scandinavia to south-central Sweden. Species distribution modelling suggests a large extension of the spatial distribution during the last glacial maximum, but highlights strong retractions to a few mountain areas under current conditions. These findings, combined with our genetic data, suggest a more or less continuous distribution of L. helle throughout central Europe at the end of the last ice age. As a consequence of postglacial warming, the species retreated northwards to Fennoscandia and escaped increasing temperatures through altitudinal shifts. Therefore, the species is today restricted to population remnants located at the mountain tops of western Europe, genetically isolated from each other, and evolved into genetically unique entities. Rising temperatures and advancing habitat destruction threaten this wealth of biodiversity. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101, 155,168. [source] | |||||||||||||