Induction of embryonic dormancy in the calanoid copepod Acartia hudsonica: heritability and phenotypic plasticity in two geographically separated populations

The planktonic copepod Acartia hudsonica apparently requires summer diapause or dormancy to persist in Narragansett Bay, RI. In estuaries to the north, however, active A. hudsonica populations are present year-round and may not express dormancy. Using a full-sibling rearing design and analysis of variance (ANOVA), I assessed the importance of phenotypic and genetic sources of variation in two geographically separate populations, one from Maine and one from Rhode Island. Both populations showed phenotypic plasticity in the percentage of dormant eggs produced. Moreover, experiments revealed significant sibship-environment interactions in both populations, indicating that the phenotypic plasticity has a genetic component. Both populations also revealed a significant amount of genetic variation in the percentage of dormant eggs produced. For the Maine population, broad sense heritability was high (0.91, 1.10) in two short-day (12L:12D) treatments and near zero (0.08) in the long-day treatment (15L:9D). For a Rhode Island population, broad sense heritability was higher (0.95) in a low-temperature short-day treatment (13.5 °C, 12L:12D) than in a high-temperature short-day treatment (17.5 °C, 12L:12D; h²=0.25).     

A simple genetic model with non-equilibrium dynamics

 It is implicit in earlier work that simple population genetic models with constant fertility selection at one locus with two alleles can have non-equilibrium dynamics. But the nature of these dynamics has never been investigated in detail. We show that locally stable 2-cycles occur in these models, which seems to be the simplest genetic models exhibiting such dynamics. Received: 5 December 1996 / Revised version: 14 November 1997     

The use of quantitative traits in the study of human population structure

Studies of human population structure and history have tended to use demographic and/or serological data for analysis. This paper reviews the methods and studies that incorporate quantitative traits (usually polygenic traits) in such analyses. Methods of assessing the degree and pattern of among-group variation are discussed, and are characterized as being model-free or model-bound. Model-free methods deal with the measure of overall populational differentiation and with comparative methods for describing the pattern of differentiation. Model-bound methods are used for direct incorporation into theoretical models of population structure in order to estimate genetic parameters, such as those in admixture and isolation by distance models. To date, studies have indicated that quantitative traits may often be used successfully in studies of human population structure, and show effects of microevolutionary forces on quantitative variation among populations.     

ESR studies on the orientation of cholesteryl ester in phosphatidylcholine multilayers

The alignment of cholesteryl esters in multilayer phosphatidylcholine membranes was investigated using two spin-labelled cholesteryl esters: 10 : 3 ester ($\text{I}$) and 1 : 14 ester ($\text{II}$). The nitroxide label of $\text{I}$ is aligned in the membrane with a very large angle of tilt (47° ± 1.5°) with respect to the normal to the membrane surface; $\text{II}$ does not show such a tilt. $\text{I}$ gives spectra corresponding to immobilized label while $\text{II}$ gives nearly isotropic spectra. Ascorbate treatment of the multilayers shows that the labels in $\text{I}$ and $\text{II}$ are not present at the phosphatidylcholine-water interphase.The data supports a ‘horseshoe’ configuration for the cholesteryl ester in the bilayer, with both the fatty acid chain and the cholesteryl moiety extending deep into the hydrophobic region of the membrane and with the ester linkage near the surface.     

Mechanisms for frequency-dependent mating success

We consider ways in which non-frequency-dependent processes could generate negatively frequency-dependent male mating success (the rare male effect). Various forms of male competition and female preference could produce the phenomenon, and further experiments are needed to examine their occurrence. We conclude that the rare male effect is likely to be of limited evolutionary relevance.     

Population structure of Alaskan and Siberian indigenous communities

Genetic data consisting of 14 red cell antigen groups and 11 serum and erythrocytic protein marker systems from four Eskimo populations of the Norton Sound area of Alaska are reported. The population structure of these four groups is analyzed both separately and within the larger context by comparison to 15 other circumpolar groups. These analyses reveal a good fit between genetic structure, geographic distribution, linguistic affiliation, and the ethnohistory of the region.     

Physical anthropology: Human evolution. By Ivan G. Pawson. Wiley,New York. 1977. x + 246 pp., figures,tables, index. $4.95 (paper)

Growth is marked by changes in body shape as well as increase in body size. It is suggested that changes in body shape in childhood and adolescence be analyzed by least squares fit lines for one dimension on a second at successive ages. These are preferred during childhood to the traditional indices of anthropologists because body proportions change with growth, and one can identify the direction of the change and observe which body dimension is changing, or if both are. Furthermore, populations may be compared by analysis of covariance for different patterns of growth related to sex and ethnic groups. Analysis of a number of populations have demonstrated clear differences between the sexes and between populations for the following body proportions: sitting height to leg length, arm length to leg length, biacromial width to biiliac width.     

Blood groups among brahmin and kamma caste populations of coastal Andhra Pradesh

Blood specimens from Brahmin and Kamma caste populations of Coastal Andhra Pradesh, India are examined for A₁A₂BO, MNSs, and Rhesus blood groups. Predominance of A group in Brahmins and B group in Kammas is observed. Phenotype A₂ records less than 4% in both populations. High frequencies of genes M, s, D, and e are exhibited among both populations. Statistically significant differences are found only for A₁A₂BO system between Brahmins and Kammas.     

Multivariate analysis of anthropometric data and classifications of British Columbian natives

Anthropometric data collected in native populations of British Columbia in the late 19th century by Franz Boas were analyzed by two multivariate techniques. Multivariate analysis of variance was used to test physical classificatory units devised by Boas and an ad hoc classification based on local cultural units. Both were found to have some empirical validity. Mahalanobis' D (Mahalanobis, '30) was computed between pairs of local groups, for both sexes. From these a matrix of differences was prepared and diagrams drawn to illustrate phenetic relationships among samples. By this means one cluster of groups, Interior B.C. peoples, could be distinguished and other local samples appeared distinctly different from each other. It was concluded that in the absence of genealogical data by which to identify local populations, local cultural units are preferable to more inclusive units for making empirical comparisons and classifications.     

The mixing behavior of pseudobinary phosphatidylcholine-phosphatidylglycerol mixtures as a function of pH and chain length

The miscibility of phosphatidylcholine (PC) and phosphatidylglycerol (PG) with different chain lengths (n = 14, 16) was examined by differential scanning calorimetry (DSC) at pH 2 and pH 7. The determination of the coexistence curves of the phase diagrams was performed using a new procedure, namely the direct simulation of the heat capacity curves as described recently (Johann et al. 1996, Garidel et al. 1997). From the simulations of the heat capacity curves first estimates for the nonideality parameters for nonideal mixing as a function of composition were obtained and phase diagrams were constructed using temperatures for the onset and offset of melting which were corrected for the broadening effect caused by a decrease in cooperativity of the transition. In most cases, the composition dependence of the nonideality parameters indicated nonsymmetric mixing behavior. The phase diagrams were further refined by simulations of the coexisting curves using a four-parameter model to account for nonideal and nonsymmetric mixing in the gel as well as in the liquid-crystalline phase. The mixing behavior of the systems was analyzed as a function of pH and chain length difference to elucidate the effect of these two parameters on the shape of the phase diagrams. At pH 7 the phase boundaries are much closer together and a narrower coexistence range is obtained compared to the corresponding phase diagrams at pH 2. For DPPC/DMPG at pH 2, the shape of the phase diagram and the strongly positive nonideality parameter ρ ₁ for the liquid-crystalline phase indicates an upper azeotropic point. This indicates an unusual behavior of the system, namely more pronounced clustering of like molecules in the liquid-crystalline phase compared to the gel phase. Received: 17 March 1997 / Accepted: 4 July 1997