[Life-history variation within a taxon: a comparative analysis of birds and mammals]. / Variabel'nost' zhiznennykh tsiklov taksona: sravnitel'nyi analiz ptits i mlekopitaiushchikh.

Most studies on life-history evolution discuss the necessity of distinguishing between extrinsic and intrinsic sources of variability in life-history traits. I use log/log plots of yearly neonate production in daugters (b) versus adult mortality (Ma) for 75 bird species and 88 mammal species to compare graphically life-history "fields" arranged by these selective forces along a "slow-fast continuum". Under the assumptions of steady-state and linear relationship between adult mortality and reproductive effort, as well as between juvenile survival and relative neonate weight, it is possible to place additional axes in the two-dimentional plot, and to predict covariations among demographic and individual growth traits. The functional regression analysis shows, that the assumptions are completely fulfilled, at least for birds, but mammals show nonlinear relationship between adult mortality and reproductive effort. This can be explained by peculiarities of metabolism and parental care in small mammals with high reproductive output. Hence, for birds the axis of relative neonate weight approximately coincides in direction with the juvenile survivorship axis, but this is not a case for mammals. In both taxa, the relative neonate weight is an invariant in relation to fecundity and adult mortality (but not in relation to adult body weight). This important feature, together with other intrinsic (energetic and phylogenetic) constraints, explains well-documented close covariations among traits, even when the effect of body size is factored out. It is argued that life-history and body size variations in birds and mammals mainly depend on a pattern of temporal resource deficiency, although this impact cannot be separated from that of extrinsic juvenile mortality.

[Optimal age of sexual maturity and limitations of juvenile survival in mammals]. / Optimal'nyi vozrast polovozrelosti i ogranicheniia na vyzhivaemost' molodi u mlekopitaiushchikh.

Although the life history evolution of small- and large-bodied mammals seems to be governed by different factors, the both shows relative neonate size and juvenile survival to be slightly dependent on body mass. I propose a hypothesis that natural selection simultaneously maximizes a time to maturity (minimizes somatic growth rate) and a number of newborn survived to reproduction. In this case optimal juvenile survival of large-bodied mammals must be close to e-beta and that of small-bodied approximately e-(1 + beta), where beta is the slope of the regression of log annual fecundity on log annual juvenile mortality. Analysis of vital characters for 71 mammal species revealed the slope to be close to unity. As a result frequency distribution of log juvenile survival shows bimodality which coincides well with predicted optimal survival for large- and small-bodies species. It is shown that the relative neonate size can be directly proportional to the juvenile survival and inversely proportional to the lifetime offspring production irrespective of mortality factors.

[Life cycle strategies: a synthesis of empirical and theoretical approaches]. / Strategii zhiznennogo tsikla: sintez émpiricheskogo i teoreticheskogo podkhodov.

A scheme of relationships among life-history characters is developed on assumptions of determinate growth and dependence of juvenile mortality on the specific growth rate. It is shown that constraints on the relative neonate size, (W0/W infinity), and minimum value of the biotic potential, (rmax), lead to "triangular" shape of life history set on the plain defined by juvenile and adult mortality. This completely coincides with the Ramenskii++--Grime (C-S-R) classification of life-history strategies. Phylogenetic constraints can reduce this set to a relatively narrow r/K-continuum specifically oriented for a certain taxon. Similar restrictions generate models of life history optimization which predict interspecific allometries between life-history traits.