Comparisons of yeast florae from natural substrates and larval guts of southwestern Drosophila

Summary The yeast florae in the natural substrates of four desert and three non-desert Drosophila species were compared both qualitatively and quantatively to the yeast present in the guts of Drosophila larvae living in those substrates. The desert species breed in rotting cacti and the other Drosophila were found breeding in necrotic oranges. Larvae of one cactophilic species, D. mojavensis, and larvae of all of the species utilizing oranges (D. melanogaster, D. pseudoobscura, and D. arizonensis) were found to contain non-random samples of the yeasts available in their respective substrates. Larval preference behavior is most likely responsible for these differences. The other cactophilic Drosophila (D. nigrospiracula, D. mettleri, and D. pachea) did not exhibit significant differences when the yeast florae of their larvae and substrates were compared. Selective feeding by larvae appears to be related to the degree of polyphagy in that only larvae of polyphagous species are selective. Trade-off between generalism and specialism at two biological levels is discussed.     

Testing the ecological relevance of Daphnia species designations

1. Molecular approaches have increasingly revealed hidden genetic structure within ecologically important species, leading to the creation of sibling species whose ecological relevance is often unclear. A prime example is Daphnia galeata mendotae, which was split into D. dentifera and D. mendotae based on differences at two allozyme loci. 2. In a set of lake populations in Michigan USA, we test the geographical and temporal consistency of the genetic structure underlying this species split. We also test the morphological relevance of this molecular variation and its ecological significance in lakes. In essence, we ask: does recognition of these new species provide valuable information for plankton ecologists? 3. We found that D. dentifera and D. mendotae represent morphologically and ecologically distinct forms that are distributed among lakes in non‐random fashion, which were remarkably stable over 6 years. Key differences between the species concern their body and head shape, vertical habitat use within lakes and distribution among lakes of different size. We hypothesise that these differences represent specialisation to habitats that differ in risk of invertebrate predation. 4. Reproductive barriers alone are insufficient to explain the pattern of genetic structure; in some lakes complete introgression is apparent. However, parent species and hybrids exhibit a stable co‐existence in many lakes, which suggests that ecological specialisation reinforces divergence within this taxon.     

Variation in the tissue water relations of two sympatric Hawaiian Dubautia species and their natural hybrid

Summary At one site of sympatry on the Island of Hawaii, Dubautia ciliolata and D. scabra are restricted to different lava flows, even though individuals of the two species may be found growing within a few meters of one another. Associated with this habitat difference is a difference in the tissue water deficits experienced by these two species. Midday water potentials in D. ciliolata are typically 0.4–0.5 MPa lower than in D. scabra.These two species also exhibit significant differences in their tissue osmotic and elastic properties. Dubautia ciliolata exhibits a lower tissue osmotic potential at full hydration and a lower tissue elastic modulus near full hydration than D. scabra. As a result, high and positive tissue turgor pressures are maintained to significantly lower tissue water contents and water potentials in D. ciliolata than in D. scabra. These differences in tissue osmotic and elastic properties appear to have a marked influence on diurnal turgor maintenance. Thus, while diurnal water potentials in D. ciliolata are significantly lower than in D. scabra, the diurnal turgor pressures exhibited by these two species are very similar.The natural hybrid between D. ciliolata and D. scabra exhibits intermediate tissue osmotic and elastic properties. This is evident, in particular, for the turgor dependence of the elastic modulus.The degree of phenotypic variation in the tissue osmotic and elastic properties of D. ciliolata appears to be relatively limited. As a result, plants of D. ciliolata growing under both well-watered conditions in the glasshouse and under natural conditions in the field exhibit a large capacity for maintaining high turgor pressures as tissue water content decreases.     

Balbiani rings and puffs of the polytene chromosomes of Drosophila auraria

Drosophila auraria and its sibling species, D. biauraria, D. triauraria, and D. quadraria are unique among Drosophila species in that their salivary gland chromosomes exhibit Balbiani rings. In this report we present a cytological map of D. auraria and information on the developmental profiles of its puffs and Balbiani rings. Information is presented on the existence of tandem inverted duplications involving the Balbiani ring regions and other regions of the chromosomes, and data are given concerning the puffing patterns of the duplicated bands. Possible homologies between puffs of D. melanogaster and D. auraria and certain differences between the two species in the developmental sequences of the active loci are discussed.     

Salivary glands of heteromyid rodents, with a summary of the literature on rodent submandibular gland morphology

The principal parenchymal elements of the submandibular glands of the heteromyid rodents Dipodomys merriami, Perognathus longimembris, Perognathus fallax, Perognathus penicillatus and Perognathus baileyi consist of acini, granular tubules and striated ducts. Acinar cells of the four species of Perognathus are aniline blue, PAS (magenta) and Alcian blue (pH 2.5) positive and metachromatic with toluidine blue and safranin. The granules of the tubule cells are orthochromatic and react with aniline blue, orange G, the PAS reagent (deep pink) and the tryptophan indicator, xanthydrol. Acinar and tubule cells of D. merriami exhibit similar reactions except for the Alcian blue stain. Acinar cells of D. merriami do not react with Alcian blue. Submandibular glands of D. merriami exhibit a sexual dimorphism of the granular tubules. There is little observable difference between the sexes in the species of Perognathus but the ratio of granular tubules to acinar elements, the degree of hypertrophy of the tubules, and the amount of mucosubstance and protein (granules) contained in their cells are different in the four species studied. Since these desert rodents have similar habitats and habits, the differences observed between the two heteromyid subfamilies studied, as well as among the four members of a single subfamily, suggest that these are inherent species variations rather than variations of adaptation to environment.     

Integrative taxonomy and evolutionary history of a newly revealed spider Dysdera ninnii complex (Araneae: Dysderidae)

The spider genus Dysdera is a species‐rich clade of specialized woodlice predators, composed typically of complexes of sibling species. Here, we analyse the Dysdera ninnii complex, distinguishing three species that exhibit slight but constant differences in the morphology of their copulatory organs, and in their genetic background. We designate a neotype for D. ninnii and redescribe it. We consider Dysdera pavesii Thorell, 1873 to be a junior synonym of Dysdera ninnii Canestrini, 1868. In addition, we describe two new species ( D ysdera moravica sp. nov. and D ysdera microdonta sp. nov. ). All three species occur in the region of north‐eastern Italy, Slovenia, and north‐western Croatia. D ysdera moravica sp. nov. expanded to central Europe. The species occur allopatrically or parapatrically. All three species possess the same diploid number and X0 sex chromosome determination. In some individuals we found chromosome fusions, and such polymorphism is common in spiders with holokinetic chromosomes. The analysis of mitochondrial (cytochrome c oxidase subunit I, COI) and nuclear ribosomal (internal transcribed spacer 2, ITS2) DNA markers revealed two clades, one formed by D. ninnii and D . microdonta sp. nov. , and a second by D . moravica sp. nov. Species of the first clade are not well defined by DNA markers. We noticed only weak separation of maternally inherited COI, and even overlap of autosomally inherited ITS2 sequences. We suggest that either short speciation time, unfinished lineage sorting, or rare hybridization events caused this pattern. In one sample of D . microdonta sp. nov. we detected the coxA gene of a Rickettsia species, which is the first record of this parasitic bacteria from the spider family Dysderidae. D ysdera microdonta sp. nov. occurs at higher altitudes than D. ninnii, and their distribution ranges form a long contact zone. Remarkably, we did not record any overlap of the two distribution ranges, suggesting that the lack of a precopulatory interspecific barrier causes a loss of reproduction potential. We hypothesize that because of the unsolved interspecific barrier together with only tiny differences in morphology and COI sequences, and no differences in karyotypes and ITS2 sequences, the D. ninnii species complex is evolutionarily young. © 2014 The Linnean Society of London     

ADAPTATIONS TO TEMPERATE CLIMATES AND EVOLUTION OF OVERWINTERING STRATEGIES IN THE DROSOPHILA MELANOGASTER SPECIES GROUP

The Drosophila melanogaster species group is considered to have originated in the tropics and only recently invaded temperate habitats. The temperate species of this group that were studied here may be subdivided into the warm-temperate species (D. lutescens and D. rufa) and the cool-temperate species (species of the auraria complex). The warm-temperate species were more cold-hardy than were their tropical relatives (D. takahashii or D. melanogaster) at the larval and imaginal stages, and the cool-temperate species were more cold-hardy than the warm-temperate species, although only at the imaginal stage. However, these species showed little or no intraspecific variation in cold-hardiness, in spite of great variation in winter temperature within the species' ranges. It is assumed that cold-hardiness is one of the main factors restricting their distributions at high latitudes and that it is the key for evolution of the warm- and cool-temperate species from their subtropical or warm-temperate ancestors. Both warm- and cool-temperate species had photoperiodically controlled reproductive diapause. In the cool-temperate species, the development of cold-hardiness was affected by diapause, but diapause had little or no effect on cold-hardiness in the warm-temperate species. Critical daylengths and the diapause rates varied from species to species according to variation in their overwintering plans and also varied geographically in consequence of their adaptation to local climates. Species showed different responses to temperature in preimaginal and ovarian development. These differences are considered to reflect adaptation to different environmental temperatures.     

How different are recently diverged species? More than 150 phenotypic differences have been reported for the D. melanogaster species subgroup.

The nine species of the Drosophila melanogaster subgroup are currently one of the best systems for studying the genetic basis of species differences and speciation. However, despite the availability of complete genome sequences from most of these species, no comprehensive accounting of their phenotypic differences has been made. We gathered data from about 200 papers published between 1919 and 2008 that report phenotypic differences between species of the D. melanogaster species subgroup and we compiled 163 morphological, physiological and behavioral traits that differ between at least two species of the D. melanogaster subgroup. Our compilation is available online at www.normalesup.org/~vorgogoz/FlyPhenomics. The FlyPhenomics database provides a useful starting point for Drosophila researchers who aim to identify the mutations underlying phenotypic variation.     

Elemental Composition in Two Water Beetles (<Emphasis Type="Italic">Dytiscus thianschanicus</Emphasis>, <Emphasis Type="Italic">Dytiscus persicus</Emphasis>) (Dytiscidae: Coleoptera) as Revealed by WDXRF Spectroscopy

In this study, concentrations of 34 different inorganic elements between Dytiscus thianschanicus and Dytiscus persicus collected from the environs of five Turkish cities were measured by wavelength dispersive X-ray fluorescence spectrometry. The two species were found to differ in both elemental composition and amount. The concentrations of Na, As, Br and Ba were found to differ significantly between D. thianschanicus and D. persicus. In addition, Mn and I concentrations for D. thianschanicus and Si, Zn for D. persicus between males and females were statistically significant. It is thought that metabolic differences between males and females of these insects may be behind the observed differences in these species. Differences in elemental composition were also seen between beetles from different localities, and the content of non-essential elements in an insect’s body may be a useful measure of the level of these elements in their habitats.     

Seasonal variation in life history traits in two Drosophila species

Seasonal environmental heterogeneity is cyclic, persistent and geographically widespread. In species that reproduce multiple times annually, environmental changes across seasonal time may create different selection regimes that may shape the population ecology and life history adaptation in these species. Here, we investigate how two closely related species of Drosophila in a temperate orchard respond to environmental changes across seasonal time. Natural populations of Drosophila melanogaster and Drosophila simulans were sampled at four timepoints from June through November to assess seasonal change in fundamental aspects of population dynamics as well as life history traits. D. melanogaster exhibit pronounced change across seasonal time: early in the season, the population is inferred to be uniformly young and potentially represents the early generation following overwintering survivorship. D. melanogaster isofemale lines derived from the early population and reared in a common garden are characterized by high tolerance to a variety of stressors as well as a fast rate of development in the laboratory environment that declines across seasonal time. In contrast, wild D. simulans populations were inferred to be consistently heterogeneous in age distribution across seasonal collections; only starvation tolerance changed predictably over seasonal time in a parallel manner as in D. melanogaster. These results suggest fundamental differences in population and evolutionary dynamics between these two taxa associated with seasonal heterogeneity in environmental parameters and associated selection pressures.     

Temperature sensitivity of circadian clocks is conserved across Drosophila species melanogaster,malerkotliana and ananassae

Light and temperature are the major environmental cycles that can synchronize circadian rhythms in a variety of organisms. Previously, we have shown that under light/dark cycles of various photoperiods, the Drosophila species ananassae exhibits unimodal activity pattern with a prominent morning activity peak in contrast with Drosophila melanogaster and Drosophila malerkotliana, which show bimodal activity pattern with morning and evening activity peaks. Here we report that circadian clocks controlling activity/rest rhythm of these two less-studied species D. malerkotliana and D. ananassae can be synchronized by temperature cycles and that even under temperature cycles D. ananassae exhibits only a pronounced morning (thermophase onset) activity peak. Although D. melanogaster and D. ananassae exhibit differences in the phase of activity/rest rhythm under temperature cycles, circadian clocks of both show similar sensitivity to warm temperature pulses. Circadian period of activity/rest rhythm of D. ananassae differs from the other two species at some moderate-range temperatures; however, in conditions that are more extreme, circadian clocks of D. melanogaster, D. malerkotliana and D. ananassae appear to be largely temperature compensated.     

Floral and pollinator divergence in two sexually deceptive South African orchids

Two sister species in Disa section Disa were studied to evaluate the effect that minor differences in floral color, shape, and scent have on pollination. D. atricapilla and D. bivalvata have overlapping distributional ranges, occupy similar habitats, flower at the same time, and often occur sympatrically. Observations at several sites indicate that each species is pollinated almost exclusively by male wasps. D. atricapilla is pollinated by Podalonia canescens (Sphecidae), while D. bivalvata is pollinated mainly by Hemipepsis hilaris Smith (Pompilidae). Both wasp genera appear to exhibit mate-seeking behavior when approaching and visiting flowers. This together with the absence of a floral reward suggests that D. atricapilla and D. bivalvata are pollinated through sexual deception. Pollination success often appears low, but because of long floral life spans, overall fruiting success is generally high. The occasional presence of hybrids in areas of sympatry is attributed to secondary beetle pollinators. The rarity of these hybrids indicates that prefertilization barriers between the species are usually strong. This is the first report of pollination through sexual deception for southern Africa.     

Contrasting patterns of population structure in the montane caddisflies Hydropsyche tenuis and Drusus discolor in the Central European highlands

1. In this study, we compared mitochondrial sequence data (cytochrome oxidase I) to infer the population structure of the two montane caddisflies Hydropsyche tenuis and Drusus discolor. The two species are contrasting examples of montane aquatic insects with insular distributions: D. discolor is restricted to altitudes above 600 m, H. tenuis is limited to the same mountain ranges in Central Europe but inhabits lower altitudes. 2. In particular, we ask whether these two species with similar regional distributions show similar patterns of population structure and haplotype diversity, and whether any differences can be attributed to population history and/or autecology. 3. To determine the population structure of both species, we applied conventional population genetics analyses to mitochondrial sequence data. We collected and sampled 121 specimens of H. tenuis from 29 sites in 10 different regions of the Central European highlands and 138 individuals of D. discolor from 40 sites in 11 different regions. 4. Nine unique haplotypes were identified for H. tenuis and 34 for D. discolor. There were eight variable positions in H. tenuis and 41 in D. discolor. The maximum difference between haplotypes was 0.8% (4 bp) for H. tenuis and 4.2% (21 bp) for D. discolor. We observed haplotype overlap between geographic regions for both species. Analysis of molecular variance showed that two‐thirds of the total variance in H. tenuis was found among regions while in D. discolor, a larger portion of variance was found within regions and populations due to a higher number of haplotypes observed within regions. Mantel test showed a significant relationship between genetic and geographic distance in D. discolor, but no significant relationship in H. tenuis. 5. Our analyses show that, despite their very similar overall distribution pattern in Europe, the two species exhibit distinct population structures, which may reflect differences in phylogeographic history, dispersal capabilities, habitat specifity or within‐region geographic occurrence.     

Trophic interactions and habitat segregation between competing Daphnia species

Summary Two commonly coexisting species of Daphnia segregate by habitat in many stratified lakes. Daphnia pulicaria is mostly found in the hypolimnion whereas D. galeata mendotae undergoes diel vertical migration between the hypolimnion and the epilimnion. I examined how habitat segregation between these two potentially competing species might be affected by trophic interactions with their resources and predators by performing a field experiment in deep enclosures in which I manipulated fish predation, nutrient levels, and the density of epilimnetic Daphnia. The results of the experiment indicate that habitat use by D. pulicaria can be jointly regulated by competition for food from epilimnetic Daphnia and predation by fishes. Patterns of habitat segregation between the two Daphnia species were determined by predation by fish but not by nutrient levels: The removal of epilimnetic fish predators resulted in higher zooplankton and lower epilimnetic phytoplankton densities and allowed D. pulicaria to expand its habitat distribution into the epilimnion. In contrast, increased resource productivity resulted in higher densities of both Daphnia species but did not affect phytoplankton levels or habitat use by Daphnia. The two species exhibit a trade-off in their ability to exploit resources and their susceptibility to predation by fish. D. g. mendotae (the less susceptible species) may thus restrict D. pulicaria (the better resource exploiter) from the epilimnion when fish are common due to lower minimum resource requirements than those needed by D. pulicaria to offset the higher mortality rate imposed by selective epilimnetic fish predators. D. g. mendotae does not appear to have this effect in the absence of fish.     

Colonization of North America by Drosophila subobscura: Ecological analysis of three communities of drosophilids in California

We have carried out bimonthly collections of Drosophila species during a 16 month period in three localities of California (Eureka, Davis, and Gilroy). D. subobscura, which has colonized North America only a few years ago, is well established and has an annual abundance cycle similar to that observed in the Old World. The differences between the three localities account for 26.4% of the species diversity. Davis and Gilroy exhibit similarities attributable to their similar environmental conditions. Seasonality accounts for 46% and 50.4 % of the species diversity in Davis and Gilroy respectively, but only for 39.4% in Eureka. Differences between years explain only a small percentage of the total species diversity. A correspondence analysis of the association between species and months of collection shows ecological similarities between D. subobscura and the Nearctic members of the obscura species group.     

Feeding habits and dietary overlap of Naididae (Oligochaeta) from a bog stream

Feeding habits and dietary overlap of three species of naidid oligochaetes (Chaetogaster diastrophus, Dero digitata, Dero nivea) were studied during June 1982–December 1983 from a bog stream in Wisconsin, USA. Chaetogaster diastrophus primarily ingested diatoms, while D. digitata and D. nivea primarily ingested detritus. Dietary overlap was substantial (97–98%) between D. digitata and D. nivea using the dietary overlap coefficient. Dietary overlap between C. diastrophus and D. digitata was 58–62% and that between C. diastrophus and D. nivea was 51–55%. Dietary differences existed between the three species in the percentage of each major food type and diatom genera ingested, selective ingestion or avoidance of diatom genera and in the size classes (length and/or volume) of diatoms consumed. These data suggest temporal coexistence of these species may possibly be due to complex food resource partitioning, although in this habitat, C. diastrophus, D. digitata, and D. nivea did not exhibit concurrent peak abundances; thus, interspecific competition for food was minimized.     

Erysiphe kenjiana (Erysiphales), a new invasive fungus in Europe

An Asian powdery mildew fungus Erysiphe (Uncinula) kenjiana (Erysiphales, Ascomycota) has been found in Ukraine. This is the first record of this fungus in Europe. In 2007, E. kenjiana was collected on four Ulmus species in Kiev. All locations adjoined railways or an airport. Development of E. kenjiana was epiphytotic. This species was not found on elms surveyed at towns situated north-east, east or south of Kiev. The fungus may have been brought directly to Ukraine by rail or air transport. In 2008, the fungus was also collected in Chernihiv situated north-east of Kiev. It is likely that E. kenjiana will spread over all Ukraine and into countries of central and western Europe in 2009 or later. Molecular phylogenetic analyses using D1/D2 domains of the 28S rDNA and ITS sequences revealed that the Ulmaceae-Cannabaceae-parasitic powdery mildews, including E. kenjiana, form a clade with strong supports, suggesting that these species diverged from a single ancestor and expanded their host ranges within the Ulmaceae and allied Cannabaceae. This hypothesis is supported by these species sharing the unique morphology of enlarged apices on their chasmothecial appendages. These fungi formed part of a larger grouping with species on Fagaceae, Nothofagaceae, Rosaceae, and Sapindaceae with strong statistical supports. These results suggest that Uncinula-like powdery mildew fungi on these plant families exhibit close evolutionary relationships with their hosts.     

Drosophila Melanogaster, Drosophila Simulans: so Similar yet so Different

During the last two decades, the two cosmopolitan species Drosophila melanogaster and Drosophila simulans have been compared with regard to numerous characteristics, ranging from their geographic distribution and ecology to their DNA polymorphism. Various traits have been compared, including morphology, physiology, sexual behavior, allozymes and other proteins, chromosomal inversions, mitochondrial and nuclear DNA, transposable elements, wolbachia etc. Such comparisons reveal similarities and differences between the two species, depending on the trait considered. In most cases, the between-population variability of D. simulans is lower than that of D. melanogaster, but the two species exhibit similar levels of within-population variability. One of the main exceptions is the nucleotide polymorphism of several nuclear regions. Although several hypotheses have been proposed to explain these observations, the evolutionary dynamics of these two species are far from being understood. How have two species sharing a common ancestor in the recent past accumulated so many differences? A brief history of comparisons of the two species, from the first in 1919 by A.H. Sturtevant, and a summary of the hypotheses proposed to explain the similarities and the differences between these species are presented and discussed.     

Tracing the origin of a cryptic invader: phylogeography of the Euwallacea fornicatus (Coleoptera: Curculionidae: Scolytinae) species complex

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Ongoing hybridization obscures phylogenetic relationships in the Drosophila subquinaria species complex

Inferring evolutionary relationships among recently diverged lineages is necessary to understand how isolating barriers produce independent lineages. Here, we investigate the phylogenetic relationships between three incompletely isolated and closely related mushroom‐feeding Drosophila species. These species form the Drosophila subquinaria species complex and consist of one Eurasian species (D. transversa) and two widespread North American species (D. subquinaria and D. recens) that are sympatric in central Canada. Although patterns of pre‐ and post‐mating isolation among these species are well characterized, previous work on their phylogenetic relationships is limited and conflicting. In this study, we generated a multi‐locus data set of 29 loci from across the genome sequenced in a population sample from each species, and then, we inferred species relationships and patterns of introgression. We find strong statistical support that D. subquinaria is paraphyletic, showing that samples from the geographic region sympatric with D. recens are most closely related to D. recens, whereas samples from the geographic region allopatric with D. recens are most closely related to D. transversa. We present several lines of evidence that both incomplete lineage sorting and gene flow are causing phylogenetic discordance. We suggest that ongoing gene flow primarily from D. recens into D. subquinaria in the sympatric part of their ranges causes phylogenetic uncertainty in the evolutionary history of these species. Our results highlight how population genetic data can be used to disentangle the sources of phylogenetic discordance among closely related species.