Pleistocene fragmentation of Amazon species' ranges

Historical patterns of connection and isolation of the impressive biological diversity of the Amazon Basin have been the subject of extensive debate, based on evidence drawn from distributional patterns of endemic species, vegetation histories from palynological studies, and geological studies. We develop species-specific ecological niche models based on current occurrence patterns of 17 species of birds and woody plants, which we project onto modelled Pleistocene (Last Glacial Maximum) climatic patterns to reconstruct past potential distributions of each species. Forest species' distributions showed fragmentation at Last Glacial Maximum and these fragments were coincident spatially, whereas savanna species showed no clear trends. Our results suggest that past climate changes fragmented forest species' ranges within a matrix of uncertain composition.     

Towards a coherent allometric framework for individual home ranges,key population patches and geographic ranges

Spatial requirements of species have often been related to body size, usually focusing on one area variable and one taxonomic group at a time. Here, we carried out a quantitative meta‐analysis and developed a minimal model, covering different types of spatial characteristics and several species groups. In a global literature review, 46 empirical regressions on home ranges and geographic ranges were collected, covering thousands of species monitored in various countries. In addition, regional data on minimum key population patches of 167 species occurring in the Netherlands were retrieved from reports. To check consistency, a theoretical model was derived from rate and density variables based on energy equivalency. The minimum number of individuals needed to sustain a viable population was considered invariant to size. According to the equations, areas were expected to scale to mass with an exponent of 1 for the individual home range and of about ¾ for the minimum population ranges. The meta‐analysis of the empirical regressions showed that average slopes for individual home ranges were between 0.74 for cold‐blooded species and 1.05 for birds and mammals. Minimum and average species geographic range scaled to mass with exponents of 1.16–1.29 and 0.28–0.46 respectively. Allometric correlations for the minimum key patch area were weak. The intercepts indicated that carnivores require more space than equally sized herbivores, while homeotherms occupy larger areas than heterotherms. Observed slopes and intercepts were often near model estimations, but important deviations from the average level were noted as well, especially for birds. Although variability was substantial in some cases, allometric approaches can contribute considerably to understanding and protecting area requirements of species.     

Entrainment ranges of forced phase oscillators

In the vertebrate spinal cord, a neural circuit called the central pattern generator produces the basic locomotory rhythm. Short and long distance intersegmental connections serve to maintain coordination along the length of the body. As a way of examining the influence of such connections, we consider a model of a chain of coupled phase oscillators in which one oscillator receives a periodic forcing stimulus. For a certain range of forcing frequencies, the chain will match the stimulus frequency, a phenomenon called entrainment. Motivated by recent experiments in lampreys, we derive analytical expressions for the range of forcing frequencies that entrain the chain, and how that range depends on the forcing location. For short intersegmental connections, in which an oscillator is connected only to its nearest neighbors, we describe two ways in which entrainment is lost: internally, in which oscillators within the chain no longer oscillate at the same frequency; and externally, in which the the chain no longer has the same frequency as the forcing. By analyzing chains in which every oscillator is connected to every other oscillator (i.e., all-to-all connections), we show that the presence of connections with lengths greater than one do not necessarily change the entrainment ranges based on the nearest–neighbor model. We derive a criterion for the ratio of connection strengths under which the connections of length greater than one do not change the entrainment ranges produced in the nearest–neighbor model, provided entrainment is lost externally. However, when this criterion holds, the range of entrained frequencies is a monotonic function of forcing location, unlike experimental results, in which entrainment ranges are larger near the middle of the chain than at the ends. Numerically, we show that similar non-monotonic entrainment ranges are possible if the ratio criterion does not hold, suggesting that in the lamprey central pattern generator, intersegmental connection strengths are not a simple function of the connection length.     

中国的主要山脉和山峰

基于我国的地貌特征、数字高程模型(DEM)以及数字地形模型(DTM)等资料,参考以往的研究文献,给出了我国主要山峰和山脉的分布图及相关的地理信息,为我国的宏观生态学和生物地理学研究提供基本的山地资料。     

Reindeer movement patterns in alpine summer ranges

To evaluate the movement rates of semi-domesticated reindeer (Rangifer tarandus tarandus) during the bare-ground season, we used successive GPS positions from 48 female reindeer. Data were collected during the summers of 2002 and 2003 in two Sámi reindeer herding districts in the Swedish mountains, Handölsdalen, and Sirges. The movement rates were analysed at five different time periods: over the whole season, and over the sub-seasons spring, and early summer, mid summer and early autumn. Variation in movements were analysed in relation to vegetation type, altitude, terrain ruggedness, temperature, wind speed, and proximity to hiking trails. We hypothesised that the foraging quality and different weather conditions is an important factor in determining movement rates. We found that reindeer movement rates were similar between study areas and were dependent on vegetation type and on weather conditions. Studying the circadian movements, in mid summer period when daytime oestrid activity are expected to be high, the reindeer stayed at higher altitudes where food quality was low, but moved to low altitudes at night where the food quality was higher. Therefore, we suggest that oestrid activity forces the reindeer to stay in low-quality vegetation types. Reindeer movements were linked to disturbance in areas of intermediate human activity. We found that in Handölsdalen, where hikers are abundant, the movement rates of reindeer decreased closer to the trails whereas in Sirges, where hikers are less abundant, the movement rates of reindeer increased closer to the trails.     

Oligotrophic spring vegetation in Spanish mountain ranges

Montio-Cardaminetea syntaxa occurring in the siliceous mountains of the Iberian Peninsula are reviewed. At the highest altitudes three associations are recognized in Spanish mountain ranges: one in the Pyrenees,Montio-Bryetum schleicheri (alpine-subalpine); another in the Ibero-Atlantic ranges,Stellario alsines-Saxifragetum alpigenae (oromediterranean); and a third in the Sierra Nevada,Sedo melanantheri-Saxifragetum alpigenae (oromediterranean). At slightly lower altitudes two other associations have been identified:Myosotidetum stoloniferae (supramediterranean), located in the western ranges; andSaxifragetum aquaticae (subalpine), located in the central and eastern Pyrenees. Syntaxonomically the Pyrenean associations are classified in theCardamino-Montion alliance, the Ibero-Atlantic associations in theMyosotidion stoloniferae alliance, and the Sierra Nevada association in a hypothetical Nevadan-North African alliance. A western European framework is suggested for the Spanish mountain associations which mainly show an E-W distribution pattern.     

Reference ranges of viscoelasticity of human blood

From 204 presumably healthy volunteers 113 (56 women, 57 men) were accepted as reference population for viscoelastic parameters of blood by medical history, physical examination and more than 20 laboratory controls. To avoid bias through processing or calculating, the reference ranges of human whole blood viscoelasticity were given at their native packed cell volumes (see figure 2). The ranges of normal plasma viscosity were determined as 1.16 to 1.41 mPas with the median of 1.31 mPas. The rheological parameters tested are independent of age and gender.     

Discrete-time growth-dispersal models with shifting species ranges

Many species are responding to global climate change by shifting their ranges poleward in latitude or upward in elevation. We analyze an integrodifference equation that combines growth, dispersal, and a constant-speed, climate-induced range shift and find that a shifting population can die out, even if the width of its range remains constant. We show how to determine the critical range-shift speed (for extinction) and study the effects of the growth rate and of the shape and scale of the dispersal kernel on persistence.     

Wide home ranges for widely foraging lizards

Space usage by animals may be influenced by a range of factors. In this study we investigate whether foraging behaviour affects the home range size of lizards. Two distinct tactics of foraging have been recognized in predators: sit-and-wait foraging (SW) and active foraging (AF). Foraging activity level of a data set of lizard species, mainly compiled from literature, is compared with their home range sizes. Two opposite predictions can be made about foraging in connection with home range area: on the one hand, SW species may exhibit larger home ranges due to their mating system; on the other hand, AF species have higher metabolic energy and thus food requirements and can be expected to have larger home ranges that have to yield this food. This study shows that percentage of the time moving (as an index of foraging mode) correlates positively with home range, even after correcting for body mass, and these patterns remain when phylogenetic relationships are taken into account. We thus conclude that home range areas parallel activity levels in lizards.     

Radioligand saturation binding experiments over large concentration ranges

Receptor analysis using the radioligand binding saturation method in situations requiring a large concentration range of the ligand is theoretically straightforward but in practice can be relatively difficult. In this paper we review three approaches for carrying out such experiments and assess the strengths and weaknesses of each. The three are two saturation experiments, two homologous competition experiments, and the mixed homologous saturation experiment. The best approach depends upon the experimental conditions and constraints of the system studied, but in general the mixed homologous saturation experiment appears to be the most effective at minimizing the amount of radioligand needed while providing the greatest reliability in the results.     

Trimester-specific thyroid hormone reference ranges in Sudanese women

Background

Trimester-specific reference ranges for T3, T4, and TSH need to be established in different communities. Neither Sudan nor other African countries have established trimester-specific reference ranges for TSH, free T3 (FT3), and free T4 (FT4) in healthy pregnant women. This study aimed to establish trimester-specific reference ranges for TSH, FT3, and FT4 in healthy pregnant Sudanese women.

Results

We performed a longitudinal study, which included 63 women with singleton pregnancies who were followed since early pregnancy until the third trimester. The study was performed in Saad Abu-Alela Hospital, Khartoum, Sudan, during January to October 2014. An equal number of age- and parity-matched non-pregnant women were enrolled as a control group. Basic clinical and obstetrics data were gathered using questionnaires. TSH, FT3, and FT4 levels were measured. Median (5th–95th centile) values of TSH, FT3, and FT4 were 1.164 IU/ml (0.079–2.177 IU/ml), 4.639 nmol/l (3.843–6.562 nmol/l), and 16.86 pmol/l (13.02–31.48 pmol/l) in the first trimester. Median values of TSH, FT3, and FT4 were 1.364 IU/ml (0.540–2.521 IU/ml), 4.347 nmol/l (3.425–5.447 nmol/l), and 13.51 pmol/l (11.04–31.07 pmol/l) in the second trimester. These values were 1.445 IU/ml (0.588–2.460 IU/ml), 4.132 nmol/l (3.176–5.164 nmol/l), and 12.87 pmol/l (9.807–23.78 pmol/l) in the third trimester, respectively. TSH levels increased throughout the trimesters. FT3 and FT4 levels were significantly higher in the first trimester compared with the second and third trimesters. TSH, FT3, and FT4 levels were significantly lower in pregnant women compared with non-pregnant women (P?<?0.001).

Conclusions

The present study is the first to establish trimester-specific reference ranges of TSH, FT3, and FT4 in Sudanese women with normal pregnancies. Our results suggest that pregnancy is likely to suppress TSH, T3, and T4 levels in healthy women.