Drosophila Affinis Research Articles

Hoisted with his own petard: How sex-ratio meiotic drive in Drosophila affinis creates resistance alleles that limit its spread.

Meiotic drivers are selfish genetic elements that tinker with gametogenesis to bias their own transmission into the next generation of offspring. Such tinkering can have significant consequences on gametogenesis and end up hampering the spread of the driver. In Drosophila affinis, sex-ratio meiotic drive is caused by an X-linked complex that, when in males with a susceptible Y chromosome, results in broods that are typically more than 95% female. Interestingly, D.affinis males lacking a Y chromosome (XO) are fertile and males with the meiotic drive X and no Y produce only sons-effectively reversing the sex-ratio effect. Here, we show that meiotic drive dramatically increases the rate of nondisjunction of the Y chromosome (at least 750X), meaning that the driver is creating resistant alleles through the process of driving. We then model how the O might influence the spread, dynamics and equilibrium of the sex-ratio X chromosome. We find that the O can prevent the spread or reduce the equilibrium frequency of the sex-ratio X chromosome, and it can even lead to oscillations in frequency. Finally, with reasonable parameters, the O is unlikely to lead to the loss of the Y chromosome, but we discuss how it might lead to sex-chromosome turnover indirectly.

Transposable element accumulation drives size differences among polymorphic Y Chromosomes in Drosophila.

Y Chromosomes of many species are gene poor and show low levels of nucleotide variation, yet they often display high amounts of structural diversity. Dobzhansky cataloged several morphologically distinct Y Chromosomes in Drosophila pseudoobscura that differ in size and shape, but the molecular causes of their large size differences are unclear. Here we use cytogenetics and long-read sequencing to study the sequence content of polymorphic Y Chromosomes in D. pseudoobscura We show that Y Chromosomes differ almost twofold in size, ranging from 30 to 60 Mb. Most of this size difference is caused by a handful of active transposable elements (TEs) that have recently expanded on the largest Y Chromosome, with different elements being responsible for Y expansion on differently sized D. pseudoobscura Y's. We show that Y Chromosomes differ in their heterochromatin enrichment and expression of Y-enriched TEs, and also influence expression of dozens of autosomal and X-linked genes. The same helitron element that showed the most drastic amplification on the largest Y in D. pseudoobscura independently amplified on a polymorphic large Y Chromosome in Drosophila affinis, suggesting that some TEs are inherently more prone to become deregulated on Y Chromosomes.

Sex-ratio meiotic drive and Y-linked resistance in Drosophila affinis.

Genetic elements that cheat Mendelian segregation by biasing transmission in their favor gain a significant fitness benefit. Several examples of sex-ratio meiotic drive, where one sex chromosome biases its own transmission at the cost of the opposite sex chromosome, exist in animals and plants. While the distorting sex chromosome gains a significant advantage by biasing sex ratio, the autosomes, and especially the opposite sex chromosome, experience strong selection to resist this transmission bias. In most well-studied sex-ratio meiotic drive systems, autosomal and/or Y-linked resistance has been identified. We specifically surveyed for Y-linked resistance to sex-ratio meiotic drive in Drosophila affinis by scoring the sex ratio of offspring sired by males with a driving X and one of several Y chromosomes. Two distinct types of resistance were identified: a restoration to 50/50 sex ratios and a complete reversal of sex ratio to all sons. We confirmed that fathers siring all sons lacked a Y chromosome, consistent with previously published work. Considerable variation in Y-chromosome morphology exists in D. affinis, but we showed that morphology does not appear to be associated with resistance to sex-ratio meiotic drive. We then used two X chromosomes (driving and standard) and three Y chromosomes (susceptible, resistant, and lacking) to examine fertility effects of all possible combinations. We find that both the driving X and resistant and lacking Y have significant fertility defects manifested in microscopic examination of testes and a 48-hr sperm depletion assay. Maintenance of variation in this sex-ratio meiotic drive system, including both the X-linked distorter and the Y-resistant effects, appear to be mediated by a complex interaction between fertility fitness and transmission dynamics.

Highlight--Tracking Adaptation's Role: Do Larger Populations Evolve Faster?

Highlight--Tracking Adaptation's Role: Do Larger Populations Evolve Faster?

Rhabdoviruses in Two Species of Drosophila: Vertical Transmission and a Recent Sweep

Insects are host to a diverse range of vertically transmitted micro-organisms, but while their bacterial symbionts are well-studied, little is known about their vertically transmitted viruses. We have found that two sigma viruses (Rhabdoviridae) recently discovered in Drosophila affinis and Drosophila obscura are both vertically transmitted. As is the case for the sigma virus of Drosophila melanogaster, we find that both males and females can transmit these viruses to their offspring. Males transmit lower viral titers through sperm than females transmit through eggs, and a lower proportion of their offspring become infected. In natural populations of D. obscura in the United Kingdom, we found that 39% of flies were infected and that the viral population shows clear evidence of a recent expansion, with extremely low genetic diversity and a large excess of rare polymorphisms. Using sequence data we estimate that the virus has swept across the United Kingdom within the past ∼11 years, during which time the viral population size doubled approximately every 9 months. Using simulations based on our lab estimates of transmission rates, we show that the biparental mode of transmission allows the virus to invade and rapidly spread through populations at rates consistent with those measured in the field. Therefore, as predicted by our simulations, the virus has undergone an extremely rapid and recent increase in population size. In light of this and earlier studies of a related virus in D. melanogaster, we conclude that vertically transmitted rhabdoviruses may be common in insects and that these host–parasite interactions can be highly dynamic.

Encapsulation ability: Are all Drosophila species equally armed? An investigation in the obscura group

Unable to form cellular capsules around large foreign bodies, the species Drosophila subobscura Collin in Gordon, 1936 was previously shown devoid of lamellocytes, the capsule-forming hemocytes in Drosophila melanogaster Meigen, 1830. This unusual case of deficiency in encapsulation ability was remarkable enough to motivate further investigations in phylogenetically related species of the obscura group. Like D. subobscura, the species Drosophila azteca Sturtevant and Dobzhansky, 1936, Drosophila bifasciata Pomini, 1940, Drosophila guanche Monclus, 1976, Drosophila miranda Dobzhansky, 1935, Drosophila persimilis Dobzhansky and Epling, 1944, and Drosophila pseudoobcura Frovola and Astaurov, 1929 were found to be unable to encapsulate large foreign bodies and also to lack lamellocytes. Surprisingly, Drosophila affinis Sturtevant, 1916, Drosophila tolteca Patterson and Mainland, 1944, and Drosophila obscura Fallen, 1823 were capable of mounting cellular capsules, although their encapsulation abilities remained weak. These three species were free of lamellocytes but possessed small pools of never before described “atypical hemocytes” present in the hemolymph when capsules were formed.

The effect of temperature on the relative abundance of flies of the Drosophila affinis subgroup collected near Ottawa, Ontario

The effect of temperature on the relative abundance of flies of the Drosophila affinis subgroup collected near Ottawa, Ontario

Two Consequences of Homosexual Courtship Performed by Drosophila melanogaster and Drosophila affinis Males

Two Consequences of Homosexual Courtship Performed by Drosophila melanogaster and Drosophila affinis Males

Speciation via hybrid dysgenesis: negative evidence from the Drosophila affinis subgroup

With the realization that some transposable elements cause hybrid dysgenesis in Drosophila melanogaster, have come proposals that speciation may be one result of their action. One characteristic of hybrid dysgenesis is that the progeny of dysgenic individuals exhibit an elevated mutation rate. Dysgenic speciation models were tested by studying hybrids of four interfertile species and semispecies of the Drosophila affinis subgroup. A study of the progeny of all possible mating pairs found no evidence for an increased visible mutation rate.

The effect of light on the sexual behavior of Drosophila affinis

Drosophila affinis is a species whose mating is facilitated by light. Although sexually mature D. affinis males court D. affinis males and females vigorously in the light, they do not perform any of the courtship behaviors in the dark. This lack of courtship is not caused by the males and females being unattractive in the dark, since D. affinis males and females elicit high levels of courtship from Drosophila melanogaster males in light and in darkness. Fertility tests confirmed previous observations that mating occasionally occurs in the dark, suggesting that some D. affinis males are capable of courting in the dark.

Temperature effects in relation to the patterns of distribution and abundance of three species in the Drosophila affinis subgroup

Abstract. 1. The effect of temperature on several aspects of the biology of Drosophila affinis, D.algonquin and D.athabasca were investigated in order to gain insight as to why these closely related species differ in their spatial and temporal patterns of occurrence.2. No differences exist between the three species in the effect of temperature on egg hatchability.3. Productivities of the three species were measured in a temperature gradient device. These measurements indicated that D.athabasca has an advantage in productivity over D.affinis at cooler temperatures (below 25°C). At warmer temperatures (above 25°C) the greater productivity of D.affinis makes it the better species. Drosophila algonquin, like D.athabasca, was characterized by its productivity curve as a species more adapted to cooler climates.4. The competitive abilities of the three species were measured at 25°C, at 18°C, and in an environment which fluctuated between 18 and 25°C on a daily cycle. Competitive ability was estimated on the basis of the performance of the species in two‐ and three‐species populations.5. In general, D.affinis exhibited its highest competitive ability relative to the other two species at the highest experimental temperature. D.athabasca had its highest competitive ability at the lowest temperature. The competitive ability of Ddgonquin was intermediate; less than that of D.affinis but greater than D.athabasca.6. The dependence of competitive ability and productivity on temperature is thought to be partly responsible for the differences between the species with respect to their geographic distributions and their spatial and temporal patterns in natural populations.

Temperature-Dependent Development and Competitive Ability of Three Species in the Drosophila affinis Subgroup

Temperature-Dependent Development and Competitive Ability of Three Species in the Drosophila affinis Subgroup

Courtship and Mating Sounds in Species of the Drosophila affinis Subgroup

Courtship and Mating Sounds in Species of the Drosophila affinis Subgroup

Ecological Genetics in Drosophila athabasca: Its Effect on Local Abundance

In the vicinity of Deer Isle, Maine, two members of the Drosophila affinis subgroup Drosophila athabasca and D. affinis show demographic evidence of competing with each other. When both species are plentiful in collections, their densities are negatively correlated. They separate ecologically on the basis of island area, D. athabasca being the more commonly collected species on the mainland and large islands while D. affinis is often the more common on smaller islands. The environment on islands from 10 to 30 hectares in area does not appear to be intrinsically worse for D. athabasca than that on the larger islands or the mainland. Island populations of D. athabasca have slower development and lower fertility than mainland populations. These may be important components of fitness in competitive situations. As measured by the within- and between-family components of variance for a morphological trait, wing length, island populations of D. athabasca show lower levels of genetic variability than do nearby mainland populations. Therefore they may be more inbred, and this may cause low fitness on islands. Because this area is near the northern limit of D. affinis's range, it is postulated that periodic population crashes and attendant inbreeding preadapt this species to island life, where inbreeding is a natural consequence of small population size. In general, population structure may often have significant effects on the ecology of species.

Effect of island area on Drosophila population densities.

Species of the Drosophila affinis subgroup show a positive correlation between population density and island area on islands in the vicinity of Deer Isle, Maine. The low density of flies on small islands may be due to inbreeding depression, exposure to salt spray, desiccation, or decimation by violent storms. Mushroom-feeding species of Drosophila show great year to year fluctuations in abundance on these islands, probably due to changes in the level of their resource supply. Population fluctuations and non-linear correlations between island area and population size may have complicating effects on the probability of extinction of species on different sized islands.

Induction of melanotic tumors in larvae of Drosophila affinis parasitized by the wasp, Pseudeucoila bochei

Induction of melanotic tumors in larvae of Drosophila affinis parasitized by the wasp, Pseudeucoila bochei

Protein and enzyme variation in Drosophila

1. 1. The isoenzyme patterns of alcohol dehydrogenase (ADH), glutamate dehydrogenase (GDH), and lactate dehydrogenase (LDH), and the protein banding patterns of Drosophila affinis, D. hydei, D. melanogaster, D. simulans Amherst, D. simulans Georgetown, and D. virilis Texemelucan were demonstated using anodal polyacrylamide-gel electrophoresis. 2. 2. Although some striking similarities were noted among these species, these studies demostrated distinct differences between all species, and the two varieties, of Drosophila studied. 3. 3. These results are discussed in relation to the intra- and interspecific variation among these species of Drosophila, and compared with previous studies on the isoenzymes of these species.

Salivary gland chromosome variation in the Drosophila affinis subgroup. 3. The long arm of the X chromosome in "western" and "eastern" Drosophila athabasca.

Journal Article Salivary Gland Chromosome Variation in the Drosophila affinis Subgroup: III. The long arm of the X chromosome in “western” and “eastern” Drosophila athabasca Get access DWIGHT D. MILLER, DWIGHT D. MILLER Dr. Miller is professor of zoology at the University of Nebraska; Mr. Voelker is a graduate student in the Department of Zoology of the University of Texas. University of Nebraska Department of Zoology Contribution Number 413 Search for other works by this author on: Oxford Academic PubMed Google Scholar ROBERT A. VOELKER ROBERT A. VOELKER Dr. Miller is professor of zoology at the University of Nebraska; Mr. Voelker is a graduate student in the Department of Zoology of the University of Texas. University of Nebraska Department of Zoology Contribution Number 413 Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Heredity, Volume 60, Issue 5, September 1969, Pages 231–238, https://doi.org/10.1093/oxfordjournals.jhered.a107979 Published: 01 September 1969

A Study of Key Characteristics for Distinguishing Several Drosophila affinis Subgroup Species, with a Description of a New Related Species

Certain characteristics of Drosophila affinis subgroup species reported as useful for species identification were reinvestigated in D. affinis, algonquin, athabasca, azteca, narragansett, and tolteca, and new criteria for species separation were sought. Both laboratory strains (in some cases kept at different temperatures) and wild specimens were studied. Special attention was paid to combs and other male fore- characteristics. Number of comb teeth is very useful, even though not 100% reliable, for distinguishing D. affinis from D. algon- quin. The sex comb index (length of first segment divided by length of longest comb tooth) and the tarsal segment index (length of first segment divided by length of second segment) were found to be very effective for separating D. affinis from athabasca and appear likely to be useful for separating D. azteca from tolteca. Number of primary clasper teeth appears likely to be helpful (but not 100%) for distinguishing D. atha;basca '(8 or more) from azteca (usually 6 or less) ; these two species are often poorly distinguishable on the basis of mesonotum striping. Testis shape would seem to be a good basis for distinguishing D. algonquin (less coiled) from tolteca (more coiled). A new species, D. novitskii, is described from collections in Colorado. A modified key for separating American D. affinis subgroup species is presented.

Geographical Distributions of the American Drosophila affinis Subgroup Species

The Drosophila affinis subgroup belongs to the D. obscura group of the subgenus Sophophora Sturtevant. Except for one European species, D. helvetica Burla, 1948, the subgroup consists of eight American species: D. affinis Sturtevant, 1916; algonquin Sturtevant and Dobzhansky, 1936; athabasca Sturtevant and Dobzhansky, 1936; azteca Sturtevant and Dobzhansky, 1936; dobzhanskii Patterson, 1943; narragansett Sturtevant and Dobzhansky, 1936; seminole Sturtevant and Dobzhansky, 1936; and tolteca Patterson and Mainland, 1944. The closeness of relationship of these species is attested to not only by their morphological similarity but also by the fact that it has been possible in the laboratory to derive certain interspecific hybrids: athabasca x azteca, both reciprocal crosses (Sturtevant and Dobzhansky, 1936); algonquin 9 x athabasca d' (Miller, 1939); affinis ? x athabasca 6' (Miller, 1941); and azteca x tolteca, both reciprocal crosses (Patterson, 1954). Moreover, female algonquin-athabasca hybrids are fertile (Miller, 194L), as are both sexes of hybrids between tolteca ? 9 and azteca 6' 6' (Patterson, 1954). Since the affinis subgroup was first identified (Sturtevant and Dobzhansky, 1936), the distributions of the member species and their incidence in collections have been reported both in reports on cytological and genetic variation in the species, and in reports on Drosophila collecting and species distributionsfor example, Dobzhansky and Sokolof (1939), Miller (1939), Patterson (1943), Patterson and Wagner (1943), Dobzhansky and Epling (1944), Patterson and Mainland (1944), Novitski (1946), Spiess (1949), Patterson and Stone (1952), Williams and Miller (1952), Levitan (1954), and BuzzattiTraverso and Scossiroli (1955). These reports (and unpublished data) have not only led to extensions of previously known geographical ranges, but also have given better ideas of the limits of distribution of some of the species and of the relative frequencies of two or more of the species collected together. It is the purpose of this paper to summarize information on the distributions of the American members of the affinis subgroup, using published records and the unpublished data of the author and several other collectors.