Evolution Of Reproductive Strategies Research Articles

Death, Hope, and Sex: Life-History Theory and the Development of Reproductive Strategies [and Comments and Reply

Many social scientists reject evolutionary views of human behavior because of their supposed genetic determinism. To establish that not all evolutionary models are inherently deterministic the author first reviews the perennial adaptationist-mechanist controversy in evolutionary biology. He then outlines life-history theory a burgeoning field of biology devoted to the study of reproduction growth and development and ecology in an evolutionary context. He undertakes next to show how life-history theory can provide a satisfactory resolution to the adaptationist-mechanist debate. Combining Promislow and Harveys arguments about the role of mortality rates in the evolution of life-history traits with Belsky Steinberg and Drapers attachment-theory model of the development of alternative reproductive strategies in humans the author proposes that the allocation of reproductive (mating and parenting) effort in adults may be partially contingent on their early experience with the causes and correlates of local high death rates. The author concludes with a discussion of some implications of this proposal for the emerging field of evolutionary psychology. (authors)

Oocyte recruitment and spawning chronology in pike, Esox lucius, and muskellunge, Esox masquinongy

During the reproductive cycle, the progression of oogenesis differs markedly between northern pike, Esox lucius Linnaeus, and muskellunge, Esox masquinongy Mitchill. Both species have group-synchronous ovaries but have different oocyte recruitment strategies. Pike is a single spawner, developing eggs in a single clutch annually, whereas muskellunge is a fractional spawner, producing two clutches of eggs per year. During the spawning period in large female muskellunge, oocyte counts indicate that the second clutch of eggs is equally important to the first. An event portrait of the spawning period for muskellunge is provided, whereby arrival of adults to a spawning site, egg yield, and hatching success agree with the fractional spawner concept. A hypothesis of the temporal sequence of evolutionary relationships in recruitment of oocytes for esocoid fishes is presented. The reproductive strategy of muskellunge belongs to a common esocoid ancestor, whereas that in pike is derived and unique. The significance of this divergence in closely related species remains consistent with the ecological theory that evolution of reproductive strategies is adaptive to diverse environmental conditions.

Developmental Constraints in the Evolution of Reproductive Strategies: Telescoping of Generations in Parthenogenetic Aphids

Most animal and plant species first grow and then switch to reproduction. Some continue to grow after breeding is initiated. Parthenogenetic aphids have a different reproductive strategy. They invest in both somatic and gonadal growth during their larval development. A developmental constraint is suggested to favour the simultaneous commitment to the growth of both soma and gonads in larval life and the telescoping of generations as an effective means of maximizing the rate of increase. This constraint also explains why aphids produce their offspring singly rather than in clutches as by so doing they keep their gonads approximately the same size and so maximize the use of the energy assimilated by the soma. Key-words: Aphids, developmental constraints, reproductive strategies, telescoping of generations

Possible Pathways for the Evolution of Reproductive Strategies in Weasels and Stoats

Possible Pathways for the Evolution of Reproductive Strategies in Weasels and Stoats

Reproductive isolation between Urophora affinis and U. quadrifasciata (Diptera: Tephritidae) in British Columbia

Observations were made of the reproductive behavior of free-ranging Urophora affinis and U. quadrifasciata on their host plant, Centaurea diffusa, near Kamloops, British Columbia. The behavior of both species is similar. Courting males of both species do not distinguish between conspecific males and females until attempted copulation. Males do discriminate between conspecific and non-conspecific females. Species recognition by males occurs at the time of prospective mate selection of during precopulatory displays. Recognition is apparently based on morphological and subtle behavioral differences between the two species. Some males did attempt copulation with non-conspecific females, and these were consistently rejected by the females. Differences in the male genitalia are probably important in female recognition of males. The behavior of these two species is discussed in relation to theoretical models of the evolution of reproductive strategies.

Latitudinal Variation in Reproductive Characteristics of American Shad (Alosa sapidissima): Evidence for Population Specific Life History Strategies in Fish

The reproductive characteristics of five populations of American shad (Alosa sapidissima) on the Atlantic coast were studied. The proportion of repeat spawners increased with the latitude of the home river. Relative and absolute fecundities decreased as the proportion of repeat spawners increased. These reciprocal trends in reproductive characteristics are independent of growth parameters. The principal factor influencing reproductive strategies in shad appears to be variability in the thermal regime of the home river which influences egg and larval survival. Northern populations, spawning in environments that are thermally harsh and variable, allocate a greater proportion of their energy reserves to migration thereby ensuring higher postspawning survival. This is accomplished by reducing the energy allocated to gonads. The pattern of reproductive responses of shad to the thermal environment of the natal river is consistent with existing ecological theory concerning the evolution of reproductive strategies in response to differing environmental conditions. Available literature for several other fishes suggests that fine tuning of reproductive strategies to local environmental conditions may be widespread among fish and may be the ultimate basis for the evolution of homing. Key words: American shad, Alosa sapidissima, reproductive strategies, fecundity, frequency of reproduction, energy allocation, latitudinal variation, theoretical ecology

Measures of fitness and demographic stability.

The concepts of entropy and reproductive potential of a genotype were introduced in a previous paper [Demetrius, L. (1974) Proc. Natl. Acad. Sci. USA 71, 4645-4647] and an analoge of the fundamental theorem of natural selection was derived. This paper relates to entropy of a population with the rate of convergence of the population to the stable age distribution. I show that (i) at maximal entropy, no oscillatory components exist and the birth sequence is unaffected by perturbations in the stable age distribution; and (ii) at zero entropy, oscillatory components occur and increase as rapidly as the real exponential component in the birth sequence. These results have implications towards (i) the relation between population fitness and adaptedness, (ii) modes of selection and the evolution of reproductive strategies, and (iii) the evolution of senescence.