Life Sciences Commons^™

Evidence For The Fixation Of Gene Duplications By Positive Selection In Drosophila, Margarida Cardoso-Moreira, J. Roman Arguello, Srikanth Gottipati, Lawrence G. Harshman, Jennifer K. Grenier, Andrew G. Clark

Lawrence G. Harshman Publications

Gene duplications play a key role in the emergence of novel traits and in adaptation. But despite their centrality to evolutionary processes, it is still largely unknown how new gene duplicates are initially fixed within populations and later maintained in genomes. Long-standing debates on the evolution of gene duplications could be settled by determining the relative importance of genetic drift vs. positive selection in the fixation of new gene duplicates. Using the Drosophila Global Diversity Lines (GDL), we have combined genome-wide SNP polymorphism data with a novel set of copy number variant calls and gene expression profiles to characterize the …

Evolution Of Starvation Resistance In Drosophila Melanogaster: Measurement Of Direct And Correlated Responses To Artificial Selection, Tiffany E. Schwasinger-Schmidt, Stephen D. Kachman, Lawrence G. Harshman

Lawrence G. Harshman Publications

Laboratory selection for resistance to starvation has been conducted under relatively controlled conditions to investigate direct and correlated responses to artificial selection. With regard to starvation resistance, there are three physiological routes by which the trait can evolve: resource accumulation, energy conservation and starvation tolerance. A majority of energetic compounds and macromolecules including triglycerides, trehalose and other sugars, and soluble protein increased in abundance as a result of selection. Movement was additionally investigated with selected males moving less than control males and selected females exhibiting a similar response to selection. Results obtained from this study supported two of the possible …

Longevity-Fertility Trade-Offs In The Tephritid Fruit Fly, Anastrepha Ludens, Across Dietary-Restriction Gradients, James R. Carey, Lawrence G. Harshman, Pablo Liedo, Hans-Georg Müller, Jane-Ling Wang, Zhen Zhang

Lawrence G. Harshman Publications

Although it is widely known that dietary restriction (DR) not only extends the longevity of a wide range of species but also reduces their reproductive output, the interrelationship of DR, longevity-extension and reproduction is not well understood in any organism. Here we address the question: “Under what nutritional conditions do the longevity-enhancing effects resulting from food restriction either counteract, complement or reinforce the mortality costs of reproduction? To answer this question we designed a fine-grained DR study involving 4,800 individuals of the tephritid fruit fly Anastrepha ludens in which we measured sex-specific survival and daily reproduction in females in each …

Simpler Mode Of Inheritance Of Transcriptional Variation In Male Drosophila Melanogaster, Marta Wayne, Marina Telonis-Scott, Lisa Bono, Lawrence G. Harshman, Artyom Kopp, Sergey V. Nuzhdin, Lauren Mcintyre

Lawrence G. Harshman Publications

Sexual selection drives faster evolution in males. The X chromosome is potentially an important target for sexual selection, because hemizygosity in males permits accumulation of alleles, causing tradeoffs in fitness between sexes. Hemizygosity of the X could cause fundamentally different modes of inheritance between the sexes, with more additive variation in males and more nonadditive variation in females. Indeed, we find that genetic variation for the transcriptome is primarily additive in males but nonadditive in females. As expected, these differences are more pronounced on the X chromosome than the autosomes, but autosomal loci are also affected, possibly because of X-linked …

Biodemography Of A Long-Lived Tephritid: Reproduction And Longevity In A Large Cohort Of Female Mexican Fruit Flies, Anastrepha Ludens, James R. Carey, Pablo Liedo, Hans-Georg Müller, Jane-Ling Wang, Damla Senturke, Lawrence G. Harshman

Lawrence G. Harshman Publications

Age of sexual maturity, daily and lifetime reproductive rates, and life span were recorded in a laboratory cohort of Mexican fruit flies consisting of over 1100 females maintained individually. The results revealed that, relative to the medfly, the Mexfly is slower maturing (14 vs 17 days), more fecund (1400 vs 650–1100 eggs/female), and longer lived (50 vs 35 days). The results reinforced the generality of several earlier findings on the medfly including the deceleration of mortality at older ages and the weakness of the correlation between the rate of egg laying at early ages and both subsequent reproduction and remaining …

The Symmetry Of Longevity, Lawrence G. Harshman, Hans-Georg Müller, Xueli Liu, Yue Wang, James R. Carey

Lawrence G. Harshman Publications

We tested the hypothesis that relatively symmetrical flies live longer. Vein measurements on the left and right wings from the same individual were used to characterize bilateral symmetry in relationship to age-specific survival in defined cohorts. A longitudinal cohort study supported the hypothesis of a correlation between bilateral symmetry and longevity. For another type of experiment, wings were removed from females and males at approximately the beginning of adult life. Thus, there would be no effect of wings per se on adult survival. These wings were measured to characterize bilateral asymmetry, and the day of death of each dewinged individual …

Stochastic Dietary Restriction Using A Markov-Chain Feeding Protocol Elicits Complex, Life History Response In Medflies, James R. Carey, Pablo Liedo, Hans-Georg Müller, Jane-Ling Wang, Ying Zhang, Lawrence G. Harshman

Lawrence G. Harshman Publications

Lifespan in individually housed medflies (virgins of both sexes) and daily reproduction for females were studied following one of 12 dietary restriction (DR) treatments in which the availability of high-quality food (yeast–sugar mixture) for each fly was based on a Markov chain feeding scheme – a stochastic dietary regime which specifies that the future dietary state depends only on the present dietary state and not on the path by which the present state was achieved. The stochastic treatments consisted of a combination of one of four values of a ‘discovery’ parameter and one of three values of a ‘persistence’ parameter. …

Life Span Extension Of Drosophila Melanogaster: Genetic And Population Studies, Lawrence G. Harshman

Lawrence G. Harshman Publications

During the past two decades, genetic studies of model organisms have been the most important tool underlying advances in understanding the biological basis of aging and longevity. Drosophila melanogaster, the geneticist's "fruit fly," is a model organism because it has been the focus of genetic studies for more than 90 years. This review argues that studies on D. melanogaster will make an especially important contribution to the field of aging and longevity at the intersection of research on genetics, complex traits, and fly populations.

Five approaches have been used to study the genetics of longevity of D. melanogaster: …

Food Pulses Increase Longevity And Induce Cyclical Egg Production In Mediterranean Fruit Flies, James R. Carey, Pablo Liedo, Lawrence G. Harshman, X. Liu, Hans-Georg Müller, Linda Partridge, Jane-Ling Wang

Lawrence G. Harshman Publications

1. Inasmuch as virtually all studies on mortality and reproduction in insects are conducted under conditions in which food availability is constant, little is known about the demographic response of insects to variable food environments. For example, it is not known if and to what extent the life expectancy of insects subjected to shortages of high-quality food will increase and/or whether this increase is associated with major decreases in lifetime reproduction.

2. Therefore cohorts of 100 individual female medflies were subjected to different sets of conditions of protein availability (interspersed with sugar-only diets) including ad libitum sugar-only (no protein), ad …

Life History Response Of Mediterranean Fruit Flies To Dietary Restriction, James R. Carey, Pablo Liedo, Lawrence G. Harshman, Ying Zhang, Hans-Georg Müller, Linda Partridge, Jane-Ling Wang

Lawrence G. Harshman Publications

The purpose of this study was to investigate medfly longevity and reproduction across a broad spectrum of diet restriction using a protocol similar to those applied in most rodent studies. Age-specific reproduction and age of death were monitored for 1,200 adult males and 1,200 females, each individually maintained on one of 12 diets from ad libitum to 30% of ad libitum. Diet was provided in a fixed volume of solution that was fully consumed each day, ensuring control of total nutrient consumption for every fly. Contrary to expectation and precedence, increased longevity was not observed at any level of …

Female Sensitivity To Diet And Irradiation Treatments Underlies Sex-Mortality Differentials In The Mediterranean Fruit Fly, James R. Carey, Pablo Liedo, Hans-Georg Müller, Jane-Ling Wang, Brad Love, Lawrence G. Harshman, Linda Partridge

Lawrence G. Harshman Publications

Large-scale experiments on medflies that were subjected to sterilizing doses of ionizing radiation (plus intact controls) and maintained on either sugar-only or full, protein-enriched diets revealed that, whereas the mortality trajectories of both intact and irradiated male cohorts maintained on both diets are similar, the mortality patterns of females are highly variable. Mean mortality rates at 35 days in male cohorts ranged from 0.2 to 0.3 but in female cohorts ranged from 0.09 to 0.35, depending on treatment. The study reports three main influences: (a) qualitative differences exist in the sex–mortality response of medflies subjected to dietary manipulations and irradiation, …

"An Evolutionary No Man’S Land" And "Reply From L. G. Harshman And A. A. Hoffmann", Margarida Matos, André Levy, Henrique Teotónio, Michael R. Rose, Lawrence G. Harshman, Ary A. Hoffmann

Lawrence G. Harshman Publications

The gap between evolutionary studies in laboratory versus natural populations is a persistent problem.

Oxidative Stress Resistance: A Robust Correlated Response To Selection In Extended Longevity Lines Of Drosophila Melanogaster?, Lawrence G. Harshman, Beth A. Haberer

Lawrence G. Harshman Publications

Stress resistance is associated with longevity in Drosophila melanogaster and other model organisms used for genetic research. The present study tests for oxidative stress resistance in one set of lines selected for late-life reproduction and extended longevity. Both females and males from the selected lines were appreciably more resistant to oxidative stress than were flies from the control lines. A relative increase in oxidative stress resistance is a correlated response to selection in this laboratory selection experiment. Increased oxidative stress resistance appears to be a relatively robust correlated response to laboratory selection for late-life reproduction and extended longevity.

Ecdysteroid Titers In Mated And Unmated Drosophila Melanogaster Females, Lawrence G. Harshman, Anne M. Loeb, Beth A. Johnson

Lawrence G. Harshman Publications

Radioimmunoassay was used to determine ecdysteroid titers in mated or unmated Drosophila melanogaster females. Whole-body ecdysteroid titers increase after mating and this response is more pronounced after 12–24 hours than it is immediately after mating. In one experiment, females were mated to transgenic males deficient in accessory gland proteins to test whether these peptides mediate the observed increase in female whole-body ecdysteroid titers. Females mated to such transgenic males do not show a pronounced increase in whole-body ecdysteroid titers. The effect of mating on female hemolymph ecdysteroid titers was also investigated. Hemolymph ecdysteroid titers decrease after mating. The ecdysteroid titer …

Environmental Effects On Remating In Drosophila Melanogaster, Lawrence G. Harshman, Ary A. Hoffman, Timothy Prout

Lawrence G. Harshman Publications

The effects of density and food on remating were investigated using Drosophila melanogaster. The frequency of remating was unaffected by density for some combinations of fly strains but was reduced at low relative densities for other combinations. Until females had used most of their stored sperm, remating was less likely when food was absent or contact with food was prevented. Food availability had little effect on the incidence of remating once stored sperm were depleted and had no effect on initial virgin mating frequency. This study indicates that environmental factors can have a substantial direct influence on the frequency …

Variation In Population Sex Ratio And Mating Success Of Asexual Lineages Of Alsophila Pometaria (Lepidoptera: Geometridae), Lawrence G. Harshman, Douglas J. Futuyma

Lawrence G. Harshman Publications

Populations of Alsophila pometaria (Harris) are largely gynogenetic and composed of asexual females that must mate with a conspecific male to reproduce. Within this asexual contingent, there are a variety of electrophoretically defined multilocus genotypes. In this study we found that populations differ in sex ratio. We also found that there is an indication of differential mating success among asexual genotypes in a population of A. pometaria.

Male Effects On Fecundity In Drosophila Melanogaster, Ary A. Hoffman, Lawrence G. Harshman

Lawrence G. Harshman Publications

Effects of male Drosophila melanogaster on female fecundity and productivity were examined, considering both females held in containers with males and females exposed to male effects not involving contact. Females were more fecund when male effects were present, and the largest increase was recorded when vials were previously conditioned by males. This effect was probably due to the growth of transmitted microorganisms, which were observed on the laying surface, as further experiments with vials conditioned by virgin females showed a similar increase in fecundity. A male-specific effect was isolated by conditioning bottles containing only agar with males and virgin females. …

The Origin And Distribution Of Clonal Diversity In Alsophila Pometaria (Lepidoptera: Geometridae), Lawrence G. Harshman, Douglas J. Futuyma

Lawrence G. Harshman Publications

A survey of spatial and temporal variation in the frequency of electrophoretically defined genotypes in the geometrid moth Alsophila pometaria revealed a high diversity of uncommon or rare asexual genotypes and clinal distributions of two of the more common clones. There was substantial year-to-year variation in genotype frequencies in seven of eleven sites. Progeny tests have revealed that sexual reproduction is uncommon in two populations and that new asexual genotypes arise from the sexual population. The recurrent origin of asexual genotypes is likely to account for the high genetic and ecological diversity of the asexual contingent of this species’ populations, …