Genetic Structure of Populations. I. On the Nature of the Genetic Load in the South Amherst Population of Drosophila melanogaster

GENETIC STRUCTURE OF POPULATIONS. IV. SUMMER ENVIRONMENTAL VARIABLES AND LETHAL AND SEMILETHAL FREQUENCIES IN A NATURAL POPULATION OF DROSOPHILA MELANOGASTER

“…This relationship is manifest in the negative correlation between temperature range prior to sample collections and the lethal + semilethal (Ie + sle) frequency recovered in the samples. The significant association has been found to persist when data for collections made in 1960 (Band and Ives, 1963) and 1961, 1962(Band, 1964 are included with the previous observations spanning 1945 to 1959.…”

“…The correlation to exist for populations of Drosophila melanogaster, In the temperate zone, the frequencies of these variants within populations increase as one moves toward the equator (U.S. populations, Ives, 1954; summary for populations for many countries, Band and Ives, 1963). If temperature is related to such observations, intrapopulationally, one might expect to find a similar relationship.…”

“…In this case, higher rainfall would be associated with increased le + sle frequencies, reduced rainfall with reduced Ie + sle frequencies. The hypothesis of an inverse relationship between Ie + sle frequency and temperature range is likewise justified in that greater fluctuation between maximum and minimum tempera- Band and Ives (1961) and the experimental demonstration of viability changes among heterozygous classes in wide and narrow temperature conditions (Band, 1963) and "Diane," each bringing over 7 inches of rain to the area. Lethal + semilethal frequencies among second chromosomes are shown for those years when collections were made in the Fall.…”

“…For rainfall pattern no obvious trends in the Data on mean and range prior to collection are as described in Band and Ives (1961). Again, the environment prior to collection is defined as the 7 days preceding first collecting day.…”

“…Lethals have been defined as those chromosomes yielding no wildtypes when homozygous, semilethals as those non-lethal chromosomes having viability less than 50% mean heterozygote viability when homozygous. The method is more fully described in, and lethal + semi- 1899-1908 1909-1918 1919-1928 1929-1938 1939-1948 1949-1955 1956-1965 lethal frequencies for 1960 given in, Band and Ives (1963), the Ie + sle frequency for 1961and 1962in Band (1964. For the September, 1964 population, the le + sle frequency was found to be 34.0% (Band, 1968) .…”