GENETIC LOADS AFFECTING FECUNDITY IN NATURAL POPULATIONS OF DROSOPHILA PSEUDOOBSCURA

Abstract

ATURAL populations of every species of Drosophila studied in this respect N carry genetic loads consisting of deleterious variants, usually recessive and concealed in heterozygous condition. Numerous studies have been made on the viability components of the genetic loads, i.e., on the variants that reduce the viability of their carriers. The components that reduce the fertility have received relatively little attention. Sterility loads have been found by DOBZHANSKY, HOLZ and SPASSKY (1942), DOBZHANSKY and SPASSKY (1953) and DOBZHANSKY, SPAS-

THE FREQUENCY AND ALLELISM OF LETHAL CHROMOSOMES IN ISOLATED DESERT POPULATIONS OF DROSOPHILA PSEUDOOBSCURA

“…There is no significant difference (p = 0.6) in the frequencies of lethals among locations. These data are consistent (p = 0.1) with other results for the same chromosome over a wide geographical range SPASSKY 1953,1963;MARINKOVIC 1967).…”

Genetic Loads and Cold Temperature Resistance in Drosophila pseudoobscura

“…A similar conclusion can be drawn for genes governing cold temperature resistance and fecundity. In a previous second-chromosome study, Marinkovic (1967a) has found little evidence for linkage or pleiotropy of genes governing viability and fecundity.…”

“…Lethal chromosomes are those which, as honiozy~ gotes, produced no wild-type flies in the standard viability tests at 25° C (see Dobzhansky et al, 1963). Viability (egg-to-adult) and fecundity (egglaying capacity) of nonlethal homozygotes and of heterozygous chromosome combinations were determined at 25° C (see Dobzhansky et al, 1963;Marinkovic, 1967a). Gene arrangements were identified by the technique of Kastritsis and Crumpacker (1966).…”

“…DRAGOSLAV MARINKOVIC, DAVID w. CRUMPACKER, AND VICTOR M. SALCEDAt Rockefeller University, New York, New York 10021 Previous studies on genetic loads in natural populations of Drosophila have dealt with components of fitness, such as rate of development, viability, longevity, fecundity, and fertility (e.g., Dobzhansky and Spassky, 1953;Dobzhansky, Spassky, and Tidwell, 1963;Hiraizumi and Crow, 1960;Marinkovic, 1967aMarinkovic, , 1967b. The present experiment extends this approach to the consideration of a specific environmental factor, namely, cold temperature.…”

FITNESS AND DENSITY-DEPENDENT POPULATION GROWTH IN DROSOPHILA MELANOGASTER

“…VOLUTIONARY biologists relate certain biological phenomena with meas-E urements of fitness. Population geneticists call these biological phenomena components of fitness," which include viability (DOBZHANSKY, SPASSKY and TIDWELL 1963), fecundity (MARINKOVIC 1967), virility (BRITTNACHER 1979), developmental rate ( MARINKOVIC 1967) and sperm displacement ( PRQUT and BUNDGAARD 1977). Population ecologists have examined such traits as the intrinsic rate of increase, r, (DOBZHANSKY, LEWONTIN and PAVLOVSKY 1964), the carrying capacity, K , of a population (CARSON 1961;AYALA 1966AYALA , 1968, mate selection (EMLEN and ORING 1977) and foraging behavior (SCHQENER 1971).…”