The concept of the household: Linking behavior and genetic analyses

The household is a species-characteristic system of social, spatial, and material relations in which an individual interacts with and adjusts to his habitat. Genetically, the household can be viewed as that system and systems level in which individuals coordinate genetic and energetic investments in lineal and collateral descendants, and in which generational cohorts coordinate individual investments in their own and allied lineages. Elsewhere we have reviewed household organizations from the standpoint of behavior in evolution. Here we discuss (1) the utility of the household as an analytic concept which bridges behavior and genetics; (2) the systematic ways in which households influence kin recognition and mate choice; and (3) variation in genetic structure of household across cultures, which remains largely unexamined: —attention to such variation in conjunction with analysis of differences in household organization should yield insights into behavioral regulation of genetic exchange and the role of the household in determining local population structure.     

Phylogenetic implications of endosperm cell wall morphology in Douglasia, Androsace, and Vitaliana (Primulaceae)

We investigated differences in endosperm cell wall thickening in three genera of Primulaceae; seven species of Douglasia , 28 species of Androsace representing the four sections of the genus, and the single species of the genus Vitaliana . Endosperm cell walls have irregular wall thickenings and narrow constrictions and characterize all Douglasia species and Vitaliana , whereas evenly thickened cell walls without constrictions were found in the endosperm of Androsace and Primula . The endosperm character supports the monophyly of Douglasia and Vitaliana , and we discuss the phylogenetic implications of this conclusion.     

Modeling experimental time series with ordinary differential equations

Recently some methods have been presented to extract ordinary differential equations (ODE) directly from an experimental time series. Here, we introduce a new method to find an ODE which models both the short time and the long time dynamics. The experimental data are represented in a state space and the corresponding flow vectors are approximated by polynomials of the state vector components. We apply these methods both to simulated data and experimental data from human limb movements, which like many other biological systems can exhibit limit cycle dynamics. In systems with only one oscillator there is excellent agreement between the limit cycling displayed by the experimental system and the reconstructed model, even if the data are very noisy. Furthermore, we study systems of two coupled limit cycle oscillators. There, a reconstruction was only successful for data with a sufficiently long transient trajectory and relatively low noise level.     

Cytolytic T lymphocyte responses to metabolically inactivated stimulator cells. II. Effect of a soluble "costimulator" factor(s) in primary and secondary mixed leukocyte culture

The ability of a concanavalin A-stimulated spleen cell supernatant (“costimulator”) to overcome the effects of impaired CD and LD antigen presentation by metabolically inactivated stimulator spleen cells was examined in the primary and secondary cytolytic T lymphocyte (T_c) response. (i) Cells inactivated by ultraviolet irradiation or mild glutaraldehyde treatment, which were unable to stimulate primary cytolytic activity on their own, generated near maximal responses in the presence of costimulator. The 30-fold lower efficiency of splenic membrane fragments as antigen in primary MLC with the supernatant indicated that the damage to immunogenicity caused by membrane isolation was not equivalent to that caused by uv light and glutaraldehyde, as has previously been assumed. (ii) Comparison of the relative effects of antigen and costimulator demonstrated that costimulator played the dominant regulatory role in primary MLC, increasing sensitivity to suboptimal antigen doses 10- to 30-fold; neither antigen nor the supernatant appeared preferentially to control the strength of the secondary response. (iii) Metabolically inactivated adult and untreated neonatal spleen cells failed to release costimulator activity in response to concanavalin A. However, the ability of the neonatal cells to induce a primary cytolytic response suggested that costimulator production by the stimulator cells themselves is not essential for primary T_c activation, and supports the hypothesis that the lack of primary immunogenicity of inactivated spleen cells reflects their failure to induce costimulator production by the responder population.     

Primula tschuktschorum and Primula eximia (Primulaceae: Section Crystallophlomis): A distylous species and its homostylous derivative from the Bering Strait region,Alaska

Primula tschuktschorum Kjellman s. lat., known from Alaska and northeastern Siberia, has been the subject of many nomenclatural combinations. This paper argues the case for treating it as two species on the basis of morphology and reproductive biology.Primula tschuktschorum Kjellman s. str. is a distylous species endemic to the Bering Strait region andP. eximia Greene is a more widely distributed homostylous species. The polymorphism seen inP. eximia is attributed to ecological and phenological factors and a high degree of self-fertilization. In contrast to its distylous relative, the ability of this homostylous species to self-fertilize has enabled it to colonize recently deglaciated areas in Alaska. Because of the intramorph incompatibility system associated with distyly,P. tschuktschorum is an obligate outcrosser. Its apparent rarity may be due to a dependence on inefficient pollinators. The species deserves further study to determine if there is a need for protected status in Alaska.     

A stochastic theory of phase transitions in human hand movement

The order parameter equation for the relative phase of correlated hand movements, derived in a previous paper by Haken et al. (1985), is extended to a time-dependent stochastic differential equation. Its solutions are determined close to stationary points and for the transition region. Remarkably good agreement between this theory and recent experiments done by Kelso and Scholz (1985) is found, and new predictions are offered.     

Temporal patterning in an auditory illusion: the verbal transformation effect

When the same syllable is presented repeatedly to a human subject, it undergoes perceptual changes known as verbal transformations. However, the dynamics of such perceptual changes is poorly understood. In the present work we show that the main organization of the perceptual transitions is into pairs. This pairwise coupling is pronounced in the frequency of switching to pair members, but not in their dwell times (the time spent perceiving a given phonemic form before switching to another form). We show that the paircoupled transforms of perception have a faster and more stable dynamic than the nonpaircoupled transforms. We also demonstrate that the pairwise coupling is stronger than would be expected from random arrangement of small numbers of transforms. These characteristic patterns of verbal transforms have been predicted by a mathematical model, first proposed as a model of perceptual alternations of ambiguous visual figures. Received: 19 February 1997 / Accepted in revised form: 27 May 1997