The genetic structure of a tribal population,the Yanomama Indians. XII. Biodemographic studies

The Yanomama Indians of Southern Vanezuela and Northern Brazil are one of the largest, relatively unacculturated tribes of the tropical rain forest. Over a period of eight years data have been collected from a considerable portion of their territory on estimated age, sex ratio, fertility rates (as determined by physical examination and urine tests), and infant death rates. Although it has been impossible to collect direct data on infanticide, this subject can be approached indirectly through distortions of the sex ratio and anecdotal information. Some historical data are also available as a basis for estimating tribal expansion in the past 100 years. With this material it has been possible to construct Life Tables for the Yanomama, and to explore the results of various perturbations of the input parameters. Data are also presented on patterns of mating and reproduction: number of spouses, mean and variance in number of surviving children, frequency of “extra-marital conceptions” based on the results of extensive blood group typings, and consanguinity rates as determined by observation and computer simulation. Although we do not present the Yanomama as typical, these data are seen as providing a basis for more realistic population models than have existed in the past. In addition, the data provide a basis for relatively precise estimates of such demographic measures as Fisher's Reproductive Value, Crow's Index of Total Selection, and Weiss' Index of Growth Regulation.     

Quantification of bird migration by radar – a detection probability problem

Besides the scientific interest in the quantification of bird migration, there is an increasing need to quantify bird movements for the assessment of bird collision risk with artificial structures. In many environmental impact studies, the radar method is used in an inappropriate manner. The processing of echoes consists often of counting blips within defined screen fields, and the surveyed volume is estimated without reference to the detection probabilities of different 'target sizes' (radar cross-sections). The aim of this paper is to present a procedure to quantify bird migration reliably using radar by stating the theoretical requirements of every single step of this procedure and presenting methodological solutions using our own radar data from extensive field studies. Our methodological solutions can be applied to various radar systems, including widely used ship radar. The procedure presented involves discriminating the echoes of birds and insects and estimating the different detection probabilities of differently 'sized' birds (radar cross-sections). By ignoring the different detection probabilities, density estimations may be wrong by as much as 400%. We fear that quantification of bird migration and predicted bird numbers affected by collisions with artificial structures are in many cases based on unreliable estimates.     

Oxygen transfer deficiencies in starch-based media

Insufficient oxygen transfer in a highly viscous media with varying viscosity occurs during the degradation of starch byBacillus licheniformis. Oxygen transfer rate (OTR) decreased below 0.3 gl^–1 h^–1 for viscosities above 5 to 10 mPa.s and agitation speeds lower than 710 rev/min. Increasing agitation speeds by 30 to 50% compensated for the decrease in OTR for viscosities between 10 and 200 mPa.s. A dual impeller is considered essential for growth improvement.     

Mean growth rate when rare is not a reliable metric for persistence of species

The coexistence of many species within ecological communities poses a long‐standing theoretical puzzle. Modern coexistence theory (MCT) and related techniques explore this phenomenon by examining the chance of a species population growing from rarity in the presence of all other species. The mean growth rate when rare, , is used in MCT as a metric that measures persistence properties (like invasibility or time to extinction) of a population. Here we critique this reliance on and show that it fails to capture the effect of temporal random abundance variations on persistence properties. The problem becomes particularly severe when an increase in the amplitude of stochastic temporal environmental variations leads to an increase in , since at the same time it enhances random abundance fluctuations and the two effects are inherently intertwined. In this case, the chance of invasion and the mean extinction time of a population may even go down as increases.     

Penicillium rubens germination on desiccated and nutrient-depleted conditions depends on the water activity during sporogenesis

Fungal growth often appears in a surrounding where water and nutrients are scarce. The impact of this environment during sporogenesis on subsequent growth is often neglected.This study investigates the effect of water availability during sporogenesis on subsequent early growth. Therefore, a carbon-depleted substrate was constructed. Humidity is then the only parameter of interest. The water conditions during sporogenesis, and during subsequent growth, were varied. This is a stressing environment: no carbon source is present, and water provided solely via the vapour.The lag time, $t_l$, and initial growth rate, ${\mu }_{fp}$, of the germ tubes were monitored.The effect of $a_w$ history on germination and initial growth depends on the $RH$ of the environment. Only at low $RH$ do spores produced at low $a_w$ have a smaller $t_l$ and higher ${\mu }_{fp}$ compared to those grown at high $a_w$. This result was remarkably pronounced when the substrate was also made hydrophobic: growth only occurred when spores were developed at low $a_w$ and placed in high $RH$.Spores grown on lowered $a_w$ attract more water. It is hypothesized that this attraction affects subsequent growth behaviour, and is the reason why growth on hydrophobic glass only prevails in the condition of high $RH$ and lowered $a_w$ history.We demonstrate the influence of cultivation conditions on germination, which becomes more pronounced in a more desiccated environment.     

Song and immunological condition in male barn swallows (Hirundo rustica)

Male secondary sexual characters may have evolved as intra-or intersexual signals of male phenotypic or genetic quality.In birds, singing performance may have the function to honestlyreveal health and vigor of individual males. Infectious diseasesand poor body conditions would therefore be expected to negativelyinfluence singing performance. Since bird pathogens are knownto elicit both a humoral and a cell-mediated immune response,it can be predicted that a negative relationship exists betweensinging performance and activity of the immune system. Thisprediction was tested for the first time in this correlationalstudy. The relationships between song rate and features andhematological variables (concentration of leukocytes in peripheralblood, ratio of gamma-globulins to total plasma proteins, bloodcell sedimentation rate, hematocrit) and body condition wereanalyzed in a population of bam swallows (Hirundo rustica).Song rate was negatively correlated with lymphocyte concentrationand with the ratio of gamma-globulins to plasma proteins. Spectrographicanalysis showed that features of song were not significantlycorrelated with hematological variables or body condition. Thelevel of circulating testosterone was not correlated with songrate nor hematological variables. This study is the first toshow a correlation between a bird's singing performance andhematological profile and suggests that song rate of male barnswallows may reflect their health status. Song in this speciesmight thus have evolved because it allows prospecting femalesto assess aspects of phenotypic and/or genetic quality of potentialmates     

Distribution and redistribution of extension growth along vertical and horizontal gravireacting maize roots

Horizontal primary roots of Zea mays L. were photographed during the course of their gravireaction and during a preceding growth period in the vertical orientation. The displacement, by root elongation, of marker particles on the root surface was recorded. The particle-displacement rates were used to estimate the distribution of elemental elongation rates along opposite sides of the growing root apex. In the temperature range 21–25°C there was a stimulation of local elongation rates along the upper side of a gravireacting root and a reduction (and sometimes a cessation) of elongation along the lower side. Elemental elongation rates have been related to the development of root curvature, and the magnitude of the differential growth between upper and lower sides required for a particular rate of bending has also been estimated. The results complement, and are compatible with, findings relating to the distribution of certain endogenous growth regulators believed to participate in the gravireaction.Abbreviation RELEL relative elemental rate of elongation