The Functional Organization of Cortical and Thalamic Inputs onto Five Types of Striatal Neurons Is Determined by Source and Target Cell Identities

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Phenotypic variability in nesting success among Osmia lignaria propinqua females in a glasshouse environment: (Hymenoptera: Megachilidae)

Abstract. 1. The phenotypic variability of several estimates of fitness among seventeen nesting female O.lignaria Cresson was examined in a glasshouse provided with abundant resources.
2. Females exhibited wide variation in: (a) number of nests and cells made and in their rate of construction, (b) the incidence of mortality of offspring, and (c) the percentage of male offspring produced (52–100%).
3. In confirmation of earlier field studies: (a) more offspring of both sexes were produced during the first half of the nesting season, (b) most female offspring were produced early in the nesting season, (c) most parental investment during the last half of the flight season was made in male offspring, (d) there was a decrease in offspring size with season, with females decreasing more than males, and (e) the ratio of female/male body weight was = 1.8. These results appear to be due to ageing rather than to a reduction in resource availability.
4. No relation between female size and fecundity was evident.
5. There was no evidence that small females tended to produce a greater proportion of the smaller sex (males) than did large females.
6. Smaller offspring of both sexes had a much greater probability of dying overwinter than did large offspring. However, where the sexes overlapped in size (large males, small females), almost all females died and almost all males survived. We hypothesize that as size of offspring produced declines with season, a greater proportion of males are produced because they have a much greater probability of surviving at small body sizes.     

On the analysis of competition at the level of the individual plant

Summary The extent to which some measure of local crowding can account for the performance of individual plants is examined with reference to populations of two species of annual plant. Only a relatively small proportion of the variation in individual plant yield could be accounted for by measures of local crowding. These included the number of close neighbours, an estimate of the area available to each plant and competitive pressure. A multiple regression that took account of both emergence time and local crowding increased the proportion of variance that could be accounted for up to 50%. Computer simulations of the growth of indivudual plants in monoculture were then caried out in order to determine whether the unexplained variation resulted from fundamental flaws in the models or from unaccounted for sources of variation in the field. The results from the simulations again indicated that only a relatively low proportion of the variation in individual plant yield could be accounted for by emergence time and local density, even though these were known to be the only variables present. These findings are discussed in relation to the relative importance of one-sided and two-sided competition, and the complex cross-correlations that occur between individuals in plant populations. These two factors will make it very difficult for field workers to determine accurately what factors determine individual plant yield and in particular to predict the effects of local crowding on the performance of individual plants.     

Relationship between cell density and prolidase activity in human skin fibroblasts: effects of ascorbate and fructose

To evaluate the influence of cell density on the activity of fibroblast prolidase (EC 3.4.13.9), we determined this activity in sparse and dense cultures. We also investigated, the effects of different concentrations of β-d(?) fructose and l(+) ascorbate, which both increased cell density at confluency. For a fructose concentration of 25 mM, we observed that in the absence of glucose, intracellular total proteins increased 1.5-fold and prolidase specific activity, 1.8-fold. For ascorbate, a broad optimum concentration was found (range 0.01 – 0.50 mM). Addition to cultures of 0.1 mM ascorbate increased total proteins 1.4-fold, and doubled prolidase activity. This investigation was prompted by our previous results [J. Metab. Dis. 1983, 6, 27–31], confirmed here, and suggesting that increased prolidase activity at confluency was due to a rise in cell density.     

Muscle fine structure reflects ecotype in two nototheniids

The fine structure of swimming (pectoral) and myotomal (axial) skeletal muscle and myocardium of two species of Antarctic nototheniid fishes were studied by electron microscopy, comparing the cryopelagic Pagothenia borchgrevinki and the benthic Trematomus bernacchii . Mean fibre size varied by a factor of four among muscles within each species and may have reflected the locomotory power available, being larger in pectoral oxidative (red) and axial glycolytic (white) muscle of P. borchgrevinki . Both species use labriform locomotion, and the more active P. borchgrevinki had a greater capillary supply, expressed as a capillary to fibre ratio, than T. bernacchii to both red (3·48 ± 0·36 v . 1·63 ± 0·14, mean ±  s . e .; P  < 0·01) and white (2·70 ± 0·20 v . 1·53 ± 0·18, mean ±  s . e .; P  < 0·01) regions of the pectoral musculature. The greater aerobic scope of P. borchgrevinki was strikingly demonstrated in the higher mitochondrial content of all skeletal muscle types sampled, and the ventricular myocardium (0·269 ± 0·011 v . 0·255 ± 0·012 mean ±  s . e .; P  < 0·05). Minor differences were found in other elements of fibre composition, with the exception of a five‐fold greater lipid content in pectoral red fibres of P. borchgrevinki (0·074 ± 0·014 mean ±  s . e .) v . T. bernacchii (0·010 ± 0·003; P  < 0·05). Differences in muscle fine structure among species clearly reflected differences in their ecotype.     

ASSESSMENT OF POTENTIAL BIAS WITH SNOWSHOE HARE FECAL PELLET-PLOT COUNTS

Abstract: The fecal pellet-plot method has been used extensively for snowshoe hare (Lepus americanus) population studies across the species' range, but potential biases associated with the technique have not been addressed adequately. We studied hare pellet-plots in northern Idaho to quantify pellet decomposition rates across environmental gradients, and conducted feeding trials on captive hares to assess the role of diet on pellet production rates. We found that across our study area pellet numbers tended to be higher on plots with high vegetative cover, which likely was a reflection of hare habitat choice rather than lesser pellet decomposition in such habitat. A pellet decomposition experiment indicated that pellet persistence was negatively related to moisture level, and that pellets produced by hares during summer decomposed more quickly than those from winter. We found that only 19% of fecal pellets collected from plots located across northern Idaho were produced by hares during winter. There was a correlation between pellet numbers from plots that were pre-cleared 1 year earlier and estimated numbers of hares on 6 study areas. A similar correlation was lacking for pellet counts from uncleared plots, implying that hare population estimation via pellet-plot counts should involve plot pre-clearing. In captive studies, juvenile hares produced slightly fewer pellets per day per gram of food ingested than adults, but pellet production was similar across diets comprised of 10 different browse species. We conclude that for our study area the fecal pellet-plot method may be subject to notable pellet decomposition bias, and therefore recommend that use of the method elsewhere across the species' range be preceded by assessment of both the pellet-hare density relationship and pellet decomposition rates across habitats.     

Separating the climatic signal from tree-ring width and maximum latewood density records

We propose a technique for separating the climatic signal which is contained in two tree-ring parameters widely used in dendroclimatology. The method is based on the removal of the relationship between tree-ring width (TRW) and maximum latewood density (MXD) observed for narrow tree rings from high latitudes. The new technique is tested on data from three larch stands located along the northern timberline in Eurasia. Correlations were calculated between the temperatures of pentads (five consecutive days), TRW chronologies and MXD chronologies calculated according to the standard and proposed methods. The analysis confirms the great importance of summer temperature for tree radial growth and tree-ring formation. TRW is positively correlated with the temperature of four to eight pentads (depending on the region) at the beginning of the growth season, but MXD as obtained by the standard technique is correlated with temperature over a much longer period. For maximum density series from which the relationship between MXD and TRW has been removed (MXD′), there is a clear correlation with temperatures in the second part of the growing season. These results are consistent with the known dynamics of tree-ring growth in high latitudes and mechanisms of tree-ring formation.     

A measure of spatial stratified heterogeneity

Spatial stratified heterogeneity, referring to the within-strata variance less than the between strata-variance, is ubiquitous in ecological phenomena, such as ecological zones and many ecological variables. Spatial stratified heterogeneity reflects the essence of nature, implies potential distinct mechanisms by strata, suggests possible determinants of the observed process, allows the representativeness of observations of the earth, and enforces the applicability of statistical inferences. In this paper, we propose a q-statistic method to measure the degree of spatial stratified heterogeneity and to test its significance. The q value is within [0,1] (0 if a spatial stratification of heterogeneity is not significant, and 1 if there is a perfect spatial stratification of heterogeneity). The exact probability density function is derived. The q-statistic is illustrated by two examples, wherein we assess the spatial stratified heterogeneities of a hand map and the distribution of the annual NDVI in China.