Drosophila Willistoni Group Research Articles

Different sensory modalities are required for successful courtship in two species of the Drosophila willistoni group

During courtship, specific signals are transmitted and received between the male and the female. To understand the evolution and function of courtship behaviours, these signals must be tested individually to determine their relative effects. Drosophila species have a variety of courtship patterns that use different sensory modalities, including chemosensory, tactile, visual and auditory cues, and thus provide an opportunity for exploring different sensory modalities. In most species of the Drosophila willistoni group, males produce an auditory cue (courtship song) through wing vibration. One species, Drosophila nebulosa, does not produce an auditory signal in courtship, although both sexes perform wing-lifting movements and males fan an anal droplet towards the female. We compared the sensory modalities important for mating success in D. nebulosa and D. willistoni through a series of phenotypic manipulation experiments in which individuals had disrupted transmission or reception of signals. In D. nebulosa, females had to be able to smell, presumably to detect the anal droplet, for successful mating to occur, whereas for males of the same species, vision was essential. In contrast, no single sensory modality was absolutely necessary for D. willistoni mating success, although hearing greatly increased mating success for females and courtship song greatly increased mating success for males. Thus, these species are divergent in the sensory modalities necessary for courtship success, indicating that courtship behaviour may change rapidly within species groups.

Seasonal dynamics of a drosophilid (Diptera) assemblage and its potencial as bioindicator in open environments

Drosophila Fallen, 1823 (Diptera, Drosophilidae) is for long a well-established model organism for genetics and evolutionary research. The ecology of these flies, however, has only recently been better studied. Recent papers show that Drosophila assemblies can be used as bioindicators of forested environment degradation. In this work the bioindicator potential of drosophilids was evaluated in a naturally opened environment, a coastal strand-forest (restinga). Data from nine consecutive seasonal collections revealed strong temporal fluctuation pattern of the majority of Drosophila species groups. Drosophila willistoni group was more abundant at autumns, whereas D. cardini and D. tripunctata groups were, respectively, expressive at winters and springs, and D. repleta group at both seasons. The exotic species D. simulans Sturtevant, 1919 (from D. melanogaster group) and Zaprionus indianus Gupta, 1970 were most abundant at summers. Overall, the assemblage structure did not show the same characteristics of forested or urban environments, but was similar to the forests at winters and to cities at summers. This raises the question that this locality may already been under urbanization impact. Also, this can be interpreted as an easily invaded site for exotic species, what might lead to biotic homogenization and therefore can put in check the usage of drosophilid assemblages as bioindicators at open environments.

Male meiotic chromosomes of five species of the Drosophila willistoni group

Male meiotic chromosomes of five species of the Drosophila willistoni group

Developmental isolation and subsequent adult behavior of Drosophila paulistorum. V. Survey of six sibling species.

In an investigation into the effects of developmental isolation from all conspecifics, the Drosophila willistoni group of six sibling species responded to differing degrees: all six are reproductively isolated from D. paulistorum, the tester species. Drosophila pavlovskiana, a narrow endemic, proved the most vulnerable, responding by reducing its adult sexual isolation, if eggs, any instar, and sometimes even pupae were socially isolated. To lesser degrees, D. tropicalis and D. willistoni both produced similar results only when their eggs were isolated, i.e., when from the moment of egg deposition on, there was absolutely no contact with other flies until testing for mating behavior. The remaining siblings, D. equinoxialis and D. insularis, were immovable.

EVOLUTION OF COURTSHIP SONG AND REPRODUCTIVE ISOLATION IN THE DROSOPHILA WILLISTONI SPECIES COMPLEX: DO SEXUAL SIGNALS DIVERGE THE MOST QUICKLY?

Reproductive isolation increases with genetic distance between species. Although sexual selection may drive divergence of sexual signals and traits, causing rapid evolution of sexual isolation, quantitative data supporting this idea are rare. We examine the rates of divergence of a species-specific courtship signal, sexual isolation, and postmating isolation in the Drosophila willistoni group. Both types of isolation increase with genetic distance and postmating isolation is the most strongly correlated with genetic divergence, suggesting this has the least variable divergence rate. Song divergence is not correlated with genetic divergence. Homoplasy in song pattern results in poorly resolved phylogenies that are different from molecular phylogenies. Song evolves more quickly than sexual isolation, which evolves more quickly than postmating isolation.

A MOLECULAR PHYLOGENY OF THE DROSOPHILA WILLISTONI GROUP: CONFLICTS BETWEEN SPECIES CONCEPTS?

The six sibling species of the Neotropical Drosophila willistoni group have a long history in studies of evolutionary biology, yet to date only one molecular study, which used allozymes, has been published on the phylogeny of the group. Here we present a phylogeny of the siblings based on the sequences of two nuclear genes, period (per) and Alcohol dehydrogenase (Adh), as well as the mitochondrial gene Cytochrome oxidase I (COI). Taken individually, only per has a strong phylogenetic signal supporting a well-resolved phylogeny of the group, and this phylogeny is different from that obtained using allozymes. The COI dataset by itself produces trees that disagree with per, and neither that data nor the Adh data have a strong phylogenetic signal, as indicated by low bootstrap values for all analyses. Combining the Adh and COI datasets results in the same tree as per alone. Combining all three genes results in the same topology, which is strongly supported. Two problematic taxa, D. pavlovskiana and a "Carmody strain," which were identified as potentially separate species based on reproductive isolation, clearly cluster in the phylogenetic analyses within D. paulistorum and D. equinoxialis, respectively. Thus, there appears to be a conflict between the biological species concept and the phylogenetic species concept.

Yeast succession in the Amazon fruit Parahancornia amapa as resource partitioning among Drosophila spp.

The succession of yeasts colonizing the fallen ripe amapa fruit, from Parahancornia amapa, was examined. The occupation of the substrate depended on both the competitive interactions of yeast species, such as the production of killer toxins, and the selective dispersion by the drosophilid guild of the amapa fruit. The yeast community associated with this Amazon fruit differed from those isolated from other fruits in the same forest. The physiological profile of these yeasts was mostly restricted to the assimilation of a few simple carbon sources, mainly L-sorbose, D-glycerol, DL-lactate, cellobiose, and salicin. Common fruit-associated yeasts of the genera Kloeckera and Hanseniaspora, Candida guilliermondii, and Candida krusei colonized fruits during the first three days after the fruit fell. These yeasts were dispersed and served as food for the invader Drosophila malerkotliana. The resident flies of the Drosophila willistoni group fed selectively on patches of yeasts colonizing fruits 3 to 10 days after the fruit fell. The killer toxin-producing yeasts Pichia kluyveri var. kluyveri and Candida fructus were probably involved in the exclusion of some species during the intermediate stages of fruit deterioration. An increase in pH, inhibiting toxin activity and the depletion of simple sugars, may have promoted an increase in yeast diversity in the later stages of decomposition. The yeast succession provided a patchy environment for the drosophilids sharing this ephemeral substrate.

Evolution of the Adh locus in the Drosophila willistoni group: the loss of an intron, and shift in codon usage.

We report here the DNA sequence of the alcohol dehydrogenase gene (Adh) cloned from Drosophila willistoni. The three major findings are as follows: (1) Relative to all other Adh genes known from Drosophila, D. willistoni Adh has the last intron precisely deleted; PCR directly from total genomic DNA indicates that the deletion exists in all members of the willistoni group but not in any other group, including the closely related saltans group. Otherwise the structure and predicted protein are very similar to those of other species. (2) There is a significant shift in codon usage, especially compared with that in D. melanogaster Adh. The most striking shift is from C to U in the wobble position (both third and first position). Unlike the codon-usage-bias pattern typical of highly biased genes in D. melanogaster, including Adh, D. willistoni has nearly 50% G + C in the third position. (3) The phylogenetic information provided by this new sequence is in agreement with almost all other molecular and morphological data, in placing the obscura group closer to the melanogaster group, with the willistoni group farther distant but still clearly within the subgenus Sophophora.

Possible horizontal transfer of Drosophila genes by the mite Proctolaelaps regalis.

There is strong inferential evidence for recent horizontal gene transfer of the P (mobile) element to Drosophila melanogaster from a species of the Drosophila willistoni group. One potential vector of this transfer is a semiparasitic mite, Proctolaelaps regalis DeLeon, whose morphology, behavior, and co-occurrence with Drosophila are consistent with the properties necessary for such a vector. Southern blot hybridization, polymerase chain reaction (PCR) amplification, and DNA sequencing showed that samples of P. regalis associated with a P strain of D. melanogaster carried P element sequences. Similarly, Drosophila ribosomal DNA sequences were identified in P. regalis samples that had been associated with Drosophila cultures. These results have potentially important evolutionary implications, not only for understanding the mechanisms by which genes may be transferred between reproductively isolated species, but also for improved detection of some host-parasite and predator-prey relationships.

Role of very slightly deleterious mutations in molecular evolution and polymorphism

Several models of multiple slightly deleterious alleles are reviewed and theoretical consequences of slightly negative selection are discussed in conjunction with evolution and variation at the molecular level. Facts are organized which may be satisfactorily explained by the hypothesis of very slightly deleterious mutations. They are: (1) There appears to be an upper limit in heterozygosity for protein loci as measured by electrophoresis. (2) The excess of rare alleles is more pronounced in Drosophila than in man. (3) Correlation of heterozygosities at a locus among sibling species of the Drosophila willistoni group is too high compared to what is expected by the strict neutral theory, while it is not so among human races and between man and chimpanzee. (4) The rate of protein divergence is exceptionally high in Hawaiian Drosophila.

The evolution of selectively similar electrophoretically detectable alleles in finite natural populations.

Most of the models of population genetics are not realistic when applied to data on electrophoretic variants of proteins because the same net charge may result from any of several amino acid combinations. In the absence of realistic models they have, however, been widely used to test competing hypotheses about the origin and maintenance of genetic variation in populations. In this paper I present a general method for determining probability generating functions for electrophoretic state differences. Then I use the method to find allelic state difference distributions for selectively similar electrophoretically detectable alleles in finite natural populations. Predicted patterns of genetic variation, both within and among species, are in reasonable accord with those found in the Drosophila willistoni group by Ayala et al. (1972) and by Ayala and Tracey (1974).

GENETIC DIFFERENTIATION DURING THE SPECIATION PROCESS IN DROSOPHILA.

Evolution consists of changes in the genetic constitution (gene pool) of populations. The process of evolution may be seen in two ways-which have been called anagenesis and cladogenesis (Rensch, 1960). Changes occurring within a given phylogenetic line as time proceeds, are anagenetic evolution. They result in increased adaptation to the environment, and often reflect changes of the physical or biotic conditions of the environments. Cladogenesis occurs when a phylogenetic lineage splits into two or more independently evolving lineages. The great diversity of the living world is the result of cladogenetic evolution, which results in adaptation to a greater variety of niches, or ways of life. Among cladogenetic processes, the most decisive one is the process by which one species splits into two or more species. Species are groups of populations reproductively isolated from any other such groups. Species are independent evolutionary units. Adaptive changes occurring in an individual or population may be extended to all members of the species by natural selection; however, they cannot be passed on to different species. One of the most important questions in evolutionary genetics is the amount of genetic differentiation occurring in the speciation process. Speciation may occur by a variety of processes. In sexually reproducing organisms speciation most generally occurs according to the model of speciation. Two main stages may be recognized in this process. First, allopatric populations of the same species become genetically differentiated, mostly as a consequence of their adaptation to different environments. This genetic differentiation can only occur if the populations are geographically separated for some time, and there is no or very little migration between them. The second stage takes place when genetically differentiated populations come into geographic contact. If the gene pools of two populations are sufficiently different, progenies from interpopulational crosses are likely to have less fitness than progenies from intrapopulational crosses. Mating preferences are affected by genes. Alleles that decrease the probability of mating with individuals of a different population will, then, be selected against, while alleles increasing the probability of intrapopulational mating will be favored by natural selection. Eventually, the process may result in two reproductively isolated populations, and thus two different species. The question, how much genetic differentiation occurs in the process of speciation, must be unfolded into two separate questions concerning the two stages of the process. The first question concerns the genetic differentiation occurring between allopatric populations that are likely to give rise to different species if and when they become, at least partially, sympatric. The second question refers to the amount of genetic differentiation taking place after sympatry, when the populations become reproductively isolated. 1 This is paper number XII in a series: Enzyme variability in the Drosophila willistoni group. 2 Supported by NSF grant GB32895. 'Present address: Dept. of Biology, Brock University, St. Catherines, Ontario, Canada. 'Address: Department of Zoology, University of Indiana, Bloomington, Indiana.

GENETIC AND REPRODUCTIVE DIFFERENTIATION OF THE SUBSPECIES, DROSOPHILA EQUINOXIALIS CARIBBENSIS.

Sibling species are species morphologically so similar as to be practically indistinguishable from each other by inspection of their structural features. The Drosophila willistoni group consists of at least twelve species, six of which are siblings. Two of the sibling species, D. pavlovskiana Dobzhansky and Kastritis, and D. insularis Dobzhansky, are narrow endemics; the former in Guyana and the latter on some islands of the Lesser Antilles. The other four species, D. willistoni Sturtevant, D. equinoxialis Dobzhansky, D. paulistorum Dobzhansky and Pavan, and D. tropicalis Burla and de Canba, have wide and largely overlapping geographic distributions. The four species are sympatric through Central America and the northern half of continental South America; two or three of them are sympatric in the southern half of Mexico, the larger Caribbean islands, Peru, Bolivia, and the southern half of Brazil (Spassky et al., 1971). We have studied for several years genetic variation in the sibling species of the D. willistoni group, using techniques of gel electrophoresis and enzyme assay. D. equinoxialis consists of two subspecies, D. e. equinoxialis and D. e. caribbensis (Ayala, 1973). In this paper we report results of the study of reproductive isolation between these two subspecies, and we compare genetic variation within and between the subspecies. Ayala and Powell (1972) have

Enzyme variability in the Drosophila willistoni group. 8. Genetic differentiation and reproduction isolation between tow subspecies.

Journal Article Enzyme Variability in the Drosophila willistoni Group: VIII. Genetic differentiation and reproductive isolation between two subspecies FRANCISCO J. AYALA, FRANCISCO J. AYALA Department of Genetics, University of CaliforniaDavis, California 95616 Search for other works by this author on: Oxford Academic PubMed Google Scholar MARTIN L. TRACEY MARTIN L. TRACEY Department of Genetics, University of CaliforniaDavis, California 95616 Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Heredity, Volume 64, Issue 3, May 1973, Pages 120–124, https://doi.org/10.1093/oxfordjournals.jhered.a108367 Published: 01 May 1973

Enzyme variability in the Drosophila willistoni group. VI. Levels of polymorphism and the physiological function of enzymes.

We have studied allelic variation at 28 loci coding for soluble enzymes in three sibling species of Drosophila. The average proportion of polymorphic loci per population is 58% in D. willistoni, 71% in D. equinoxialis, and 60% in D. tropicalis. An individual of any one of these three species is heterozygous at 18–22% of its genes. The correlation between the amount of polymorphism at a given locus and the equilibrium constant of the reaction catalyzed by the corresponding enzyme is not significantly different from zero. We have separated enzymes into those involved in glucose metabolism (group I) and all other enzymes (group II). The genes coding for group II enzymes are about twice as polymorphic as those coding for group I enzymes.