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PubMed2000

Interspecific competition between sibling species larvae of Anopheles arabiensis and An. gambiae.

Mosquito larvae of the sibling species Anopheles arabiensis Patton and An. gambiae Giles sensu stricto (Diptera: Culicidae) were investigated for interspecific competition. Single-species and mixed-species populations were reared at 27 degrees C from the first instar to pupation at different densities (100, 200 or 400 larvae/200 cm2 tray) with a constant amount of food, 0.2 mg/larva/day. Pupae obtained from mixed populations were identified to species using PCR. Both species had a 1:1 sex ratio at pupation. Development time to pupation averaged about one day less for An. arabiensis compared to An. gambiae, ranging from 0.93-1.49d for males and from 0.44-0.84 d for females in single populations. In mixed species populations the difference for males ranged from 0.99-1.58d and for females from 0.93-1.62d. Survival rates of An. gambiae s.s. were significantly higher than those of An. arabiensis in both the single-species and mixed-species populations. Mixed-species rearing did not have an effect on the survival of An. gambiae, whereas the mortality rate of An. arabiensis was significantly higher in mixed populations than when only this species was reared at the same densities, suggesting a competitive disadvantage for An. arabiensis in mixed populations. High proportions of larvae (4-35%) were lost during development; these losses could not be accounted for by corpses found in the rearing pans. The possibility of cannibalism was investigated by rearing each species separately in small containers (five per 50 ml), inspected every 6h, but no cannibalism was detected at any stage of development in either species. It was concluded that, under these experimental circumstances, interspecific competition between both species did occur but with a detrimental effect on An. arabiensis only. Relevance of these findings to the ecology of both species in the field is discussed briefly.

Animals↗
PubMed1990

Invasion resistance arises in strongly interacting species-rich model competition communities.

I assemble stable multispecies Lotka-Volterra competition communities that differ in resident species number and average strength (and variance) of species interactions. These are then invaded with randomly constructed invaders drawn from the same distribution as the residents. The invasion success rate and the fate of the residents are determined as a function of community-and species-level properties. I show that the probability of colonization success for an invader decreases with community size and the average strength of competition (alpha). Communities composed of many strongly interacting species limit the invasion possibilities of most similar species. These communities, even for a superior invading competitor, set up a sort of "activation barrier" that repels invaders when they invade at low numbers. This "priority effect" for residents is not assumed a priori in my description for the individual population dynamics of these species; rather it emerges because species-rich and strongly interacting species sets have alternative stable states that tend to disfavor species at low densities. These models point to community-level rather than invader-level properties as the strongest determinant of differences in invasion success. The probability of extinction for a resident species increases with community size, and the probability of successful colonization by the invader decreases. Thus an equilibrium community size results wherein the probability of a resident species' extinction just balances the probability of an invader's addition. Given the distribution of alpha it is now possible to predict the equilibrium species number. The results provide a logical framework for an island-biogeographic theory in which species turnover is low even in the face of persistent invasions and for the protection of fragile native species from invading exotics.

Journal Article↗
PubMed2004

Ideal free distributions, evolutionary games, and population dynamics in multiple-species environments.

In this article, we develop population game theory, a theory that combines the dynamics of animal behavior with population dynamics. In particular, we study interaction and distribution of two species in a two-patch environment assuming that individuals behave adaptively (i.e., they maximize Darwinian fitness). Either the two species are competing for resources or they are in a predator-prey relationship. Using some recent advances in evolutionary game theory, we extend the classical ideal free distribution (IFD) concept for single species to two interacting species. We study population dynamical consequences of two-species IFD by comparing two systems: one where individuals cannot migrate between habitats and one where migration is possible. For single species, predator-prey interactions, and competing species, we show that these two types of behavior lead to the same population equilibria and corresponding species spatial distributions, provided interspecific competition is patch independent. However, if differences between patches are such that competition is patch dependent, then our predictions strongly depend on whether animals can migrate or not. In particular, we show that when species are settled at their equilibrium population densities in both habitats in the environment where migration between habitats is blocked, then the corresponding species spatial distribution need not be an IFD. Thus, when species are given the opportunity to migrate, they will redistribute to reach an IFD (e.g., under which the two species can completely segregate), and this redistribution will also influence species population equilibrial densities. Alternatively, we also show that when two species are distributed according to the IFD, the corresponding population equilibrium can be unstable.

Animal Migration↗
PubMed2005

Photosynthetic acclimation to light changes in tropical monsoon forest woody species differing in adult stature.

We studied morphological and physiological leaf and whole-plant features of seedlings of six late-successional woody species common in the Xishuangbanna lowland rain forest in southwest China. Study species differed in adult stature and shade tolerance and included the shrubs Lasianthus attenuatus Jack and Lasianthus hookeri C.B. Clarke ex Hook. f.; the sub-canopy species Barringtonia macrostachya (Jack) Kurz and Linociera insignis C.B. Clarke; the canopy tree Pometia tomentosa (Blume) Teijsm. & Binn.; and the emergent species Shorea chinensis (Wang Hsie) H. Zhu. After 1 year of growth in low light (4.5% full sun), seedlings were transferred to high light (24.5% full sun) to investigate acclimation responses of existing leaves to forest gap opening and to determine whether seedling capacity for acclimation is a limiting factor in its natural regeneration. Leaves of the shrub species are shade-adapted, as indicated by their low photosynthetic capacity, efficiency in using sunflecks, low stomatal density, low Chl a/b ratio and high spongy/palisade mesophyll ratio. The shrub species utilized sunflecks efficiently because they had a short photosynthetic induction time and low induction loss. In all species, transfer of seedlings to high light resulted in a substantial initial reduction in the dark-adapted quantum yield of photosystem II (variable chlorophyll fluorescence/maximum chlorophyll fluorescence; Fv/Fm) at midday. Predawn Fv/Fm of the taller species did not change greatly, but predawn Fv/Fm of the shrub species decreased significantly without complete recovery within 25 days of transfer to high light, indicating chronic photoinhibition and damage to the previously shade-adapted leaves. Maximum net photosynthetic rate and dark respiration of the four taller species increased considerably after transfer to high light, but not in the shrub species. Similar trends were observed for the number of newly formed leaves and relative height growth rate. We conclude that the shrubs L. hookeri and L. attenuatus have limited potential for developmental and physiological acclimation to high light, which explains their absence from forest gaps. Compared with the shrub species, the taller tree species, which are more likely to experience high light during their life span, showed a greater potential for light acclimation. Physiological differences among the four tree species were not consistent with differences in adult stature.

Acclimatization↗
PubMed2002

Evolutionary relationships among rice species with AA genome based on SINE insertion analysis.

Previous studies based on morphological and molecular markers indicated that there are two cultivated and five wild rice species within the Oryza genus with the AA genome. In the cultivated rice species, Oryza sativa, a retroposon named p-SINE1 has been identified. Some of the p-SINE1 members characterized previously showed interspecific insertion polymorphisms in the species with the AA genome. In this study, we identified new p-SINE1 members showing interspecific insertion polymorphisms from representative strains of four wild rice species with the AA genome: O. barthii, O. glumaepatula, O. longistaminata, and O. meridionalis. Some of these members were present only in strains of one species, whereas the others were present in strains of two or more species. The p-SINE1 insertion patterns in the strains of the Asian and African cultivated rice species O. sativa and O. glaberrima were very similar to those of the Asian and African wild rice species O. rufipogon and O. barthii, respectively. This is consistent with the previous hypothesis that O. sativa and O. glaberrima are derived from specific wild rice species. Phylogenetic analysis based on the p-SINE1 insertion patterns showed that the strains of each of the five wild rice species formed a cluster. The strains of O. longistaminata appear to be distantly related to those of O. meridionalis. The strains of these two species appear to be distantly related to those of three other species, O. rufipogon, O. barthii and O. glumaepatula. The latter three species are closely related to one another with O. barthii and O. glumaepatula being most closely related. A phylogenetic tree including a hypothetical ancestor with all loci empty for p-SINE1 insertion showed that the strains of O. longistaminata are related most closely to the hypothetical ancestor. This indicates that O. longistaminata and O. meridionalis diverged early on, whereas the other species diverged relatively recently, and suggests that the Oryza genus with AA genome might have originated in Africa, rather than in Asia.

Base Sequence↗
PubMed2005

Some characteristics of the larval breeding sites of Anopheles culicifacies species B and E in Sri Lanka.

BACKGROUND & OBJECTIVES: Anopheles culicifacies Giles, the major malaria vector in Sri Lanka, exists as a species complex comprising two sympatric sibling species--species B and E. Species E is reported to be the major vector of Plasmodium vivax and P. falciparum parasites in Sri Lanka, whilst species B is a poor or nonvector as in India. Knowledge of the breeding habits of the two sibling species can help in designing optimal vector control strategies. Hence, a survey was conducted in Sri Lanka to study the preferential breeding habitats of An. culicifacies species B and E. METHODS: Immature forms of An. culicifacies were collected from identified breeding sites in malarious districts. Collected larvae were typed for their sibling species status based on mitotic Y-chromosome structure. Data was analysed using Statistical Package for Social Science version 10.0. RESULTS: An. culicifacies immature forms were found in 23 collection sites. Among these samples 19 were found to have species E and four to have species B. All species B larvae were collected from Tonigala village in the Puttalam district. None of the 23 sites was found to have both species B and E. Species E, the major vector of malaria, appears to breed in variety of breeding sites which can be of an indication of its adaptive variation to exploit breeding sites with varying limnological characteristics. INTERPRETATION & CONCLUSION: The present findings have to be taken into account when formulating more effective larval control measures. They also show the need for a detailed study of possible different preferences for larval breeding sites between species B and E.

Animals↗
PubMed1990

Ribonuclease in different chromosomal species of the mole rat, superspecies Spalax ehrenbergi: concentration in the pancreas and primary structure.

Ribonucleases are found in considerable quantities in the pancreas of a number of mammalian taxa and a few reptiles. The ribonuclease content varies greatly in different species. Large quantities are found in ruminants and species that have a ruminant-like digestion and in a number of species with coecal digestion. This is a response to the necessity of digesting large amounts of RNA derived from the microflora of the stomach of ruminants or species with ruminant-like digestion or of the coecum of species with coecal digestion. The amino acid sequence of pancreatic ribonuclease from the chromosomal species 2n = 60 of the mole rat, superspecies Spalax Ehrenbergi was determined. From the comparison of the sequence with those of other mammalian species we found that Spalax diverged from the myomorph rodent branch before the divergence of the Muridae (mouse, rat) from the Cricetidae (hamster, muskrat). Spalax ribonuclease shares several amino acid residues with other myomorph rodent species. These are not or only rarely observed outside this rodent suborder. Although the ribonuclease content varies greatly in different mammalian species, the variation in content between individuals within a species is small. Spalax is an exception to this with ribonuclease contents varying over more than an order of magnitude in different individuals. Ribonucleases isolated from the chromosomal species 2n = 52, 2n = 58 and 2n = 60 have identical elution positions on reversed-phase HPLC. The enzyme from the 2n = 54 species, however, elutes at a slightly earlier elution position. No amino acid sequence differences have been found hitherto between the ribonucleases of the four chromosomal species of Spalax ehrenbergi occurring in Israel. However, due to lack of material we were unable to determine more than about 20% of the sequence of the enzyme from the 2n = 54 species, which is the oldest offshoot.

Amino Acid Sequence↗
PubMed1989

Aquatic fungi associated with seven species of Nile fishes (Egypt).

Ten identified species in addition to 2 unidentified species of Achlya and Pythium which belong to seven zoosporic fungal genera (aquatic freshwater fungi) were recovered during this investigation. The fish species with most zoosporic fungi (5 species and 3 genera) was Tilapia nilotica. The fish species with least fungi were Bagrus bayad and Syndontis schall (yielded only one species each). Mormyrus kannum did not give any zoosporic fungal species. Some aquatic fungi emerged only from internal organs of some fish species. 46 species belonging to 22 terrestrial fungal genera were also recovered during this work. The broadest spectrum (15 species) was recorded in the second external wash water (WE2) of Mormyrus kannum and the narrowest spectrum (2 species) in the second internal wash water (WI2) of Schilbe mystus and with the scales of Labeo niloticus. First wash water of internal organs (WI1) of Tilapia nilotica yielded the highest total count (6.95% of total count) and the second wash water of internal organs (WI2) of Schilbe mystus yielded the lowest total count (0.34% of total count). Nile water sample (NW) yielded 3.67% of total fungi and eight species which belong to seven genera. Aspergillus was the most common (31 out of 31 samples) and yielded 52.40% of total fungi. It was represented by 12 species and one variety of A. flavus var. columnaris (broadest spectrum). Penicillium was represented by 7 species and found in 19 out of 31 samples yielding 11.02% of total fungi.

Animals↗
PubMed1998

Comparison of three estimators of species richness in parasite component communities.

Comparisons of species richness between parasite component communities are often confounded by uneven sampling effort and the possibility that rare species have been missed from some component communities. The use of nonparametric estimators of species richness could potentially alleviate this problem by allowing the number of missing species to be extrapolated from the observed data. The performance of 3 estimators and their sensitivity to true species richness and the frequency of rare species, i.e., species with low prevalence, were tested using computer-simulated parasite communities. When the number of hosts examined in a sample is large, the observed species richness is an accurate estimate of true richness; no extrapolation is necessary even when rare species make up a large part of the community. At small sample sizes, observed species richness is a poor underestimate of true richness. The jackknife estimator and Chao's estimator both improve the estimate of species richness, but they are imprecise and can seriously overshoot the true richness value when the community includes many rare species. The bootstrap estimator. on the other hand, gives a better estimate than observed richness. Bootstrap estimates are also less variable and less likely to overestimate true richness, independently of how frequent rare species are in the community. This estimator provides a better, but conservative, estimate of true richness than observed richness and should be used to correct for inadequate host sampling. Data from natural communities suggest that the use of richness estimators is often justified, and that many parasite species may regularly escape detection.

Animals↗
PubMed2026

PCR-based species identification tools for wireworms (Coleoptera: Elateridae) of economic importance in Canada.

BACKGROUND: Coexistence of pest and non-pest wireworms (Coleoptera: Elateridae) in agricultural fields makes species-level identification critical to determine when pest management measures are required. However, morphological identification of wireworms (larval stage of click beetles) is challenging, as larvae are difficult to distinguish based on morphological features and misidentifications are common. Here, we developed species-specific primers for 15 click beetle species to be used in PCR-based species-level identification for agricultural fields across Canada. RESULTS: Partial sequences of the gene regions cytochrome c oxidase I (COXI), 16S, 12S, 28S, 18S, internal transcribed spacer 2 (ITS2), cytochrome-b (CYTB), elongation factor 1 (EF1), ATP6/8, NADH dehydrogenase 1 (ND1), NADH dehydrogenase 2 (ND2), NADH dehydrogenase 3 (ND3), NADH dehydrogenase 4 (ND4), NADH dehydrogenase 5 (ND5) and NADH dehydrogenase 6 (ND6) were generated for elaterid species of interest. Of these gene regions, primers were designed on the mitochondrial gene regions COXI, CYTB and ND1 that had sufficient variation to discriminate among species and tested for species specificity using additional pest and non-pest species from the families Elateridae, Carabidae, Scarabidae and Silphidae. Specificity testing confirmed that all primer sets were species-specific. CONCLUSION: The novel primers designed in this study allow for PCR-based species identification of 15 economically important click beetle pest species in Canada. Further testing is needed to validate the assay for use outside of Canada. Accurate species-level identification will benefit pest management professionals by informing management decisions and reducing the use of insurance insecticide applications due to difficulties with identifications of wireworm pest species. © 2026 His Majesty the King in Right of Canada and The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. Reproduced with the permission of the Minister of Agriculture and Agri-Food.

Animals↗
PubMed2002

Role of reactive oxygen and nitrogen species in acute respiratory distress syndrome.

Reactive oxygen species are reactive, partially reduced derivatives of molecular oxygen (O 2 ). Important reactive oxygen species in biologic systems include superoxide radical anion, hydrogen peroxide, and hydroxyl radical. Closely related species include the hypohalous acids, particularly hypochlorous acid; chloramine and substituted chloramines; and singlet oxygen. Reactive nitrogen species are derived from the simple diatomic gas, nitric oxide. Peroxynitrite and its protonated form, peroxynitrous acid, are the most significant reactive nitrogen species in biologic systems. A variety of enzymatic and nonenzymatic processes can generate reactive oxygen species and reactive nitrogen species in mammalian cells. An extensive body of experimental evidence from studies using animal models supports the view that reactive oxygen species and reactive nitrogen species are important in the pathogenesis of acute respiratory distress syndrome. This view is further supported by data from clinical studies that correlate biochemical evidence of reactive oxygen species-mediated or reactive nitrogen species-mediated stress with the development of acute respiratory distress syndrome. Despite these data, pharmacologic strategies directed at minimizing reactive oxygen species-mediated or reactive nitrogen species-mediated damage have yet to be successfully introduced into clinical practice. The most extensively studied compound in this regard is N -acetylcysteine; unfortunately, clinical trials with this compound in patients with acute respiratory distress syndrome have yielded disappointing results.

Animals↗
PubMed1978

The distribution of satellite and main-band DNA components in the melanogaster species subgroup of Drosophila. I. Fractionation of DNA in actinomycin D and distamycin A density gradients.

Fractionation of total adult DNA of five of the seven species of the melanogaster species sub-group of Drosophila in actinomycin D and distamycin A caesium density gradients has revealed the presence of three main-band DNA components, common to all species, and ten satellite DNAs that are distributed between the species. Satellite DNAs are either unique to a species or common to two or more species. The abundance of a common satellite DNA varies between species. There is no simple relationship between the presence of a satellite DNA and a branch point of phylogenetic divergence; nevertheless the arrangement of the species in a phylogeny that is based on the numbers of satellites held in common accurately reflects the pattern of relationships between the same species based on differences in inversions of polytene chromosomes. The species can be similarly arranged according to the compositions of their mitochondrial DNAs. It is possible that the same basic set of sequences, each of low frequency, is common to all species with arbitrary or selected amplification of particular sequences to differing extents in individual species. The conservation of satellites in the group and the close parallel between the distributions of satellites and inversions between the species suggests that either the processes that operate to change both chromosomal phenomena are similarly time-dependent and occurring at relatively low rates or that their rates of change are restricted according to some undetermined functions of these aspects of the genome.

Animals↗
PubMed1976

DNA homologies among homothallic, pseudo-homothallic and heterothallic species of Neurospora.

Highly purified DNAs from three homothallic species Neurospora africana, N. dodgei and N. lineolata; three reference strains representing authentic heterothallic species, N. crassa, N. intermedia and N. sitophila; and two strains of pseudo-homothallic species N. tetrasperma were characterized by spectrophotometry and DNA reassociation using hydroxyapatite chromatography. All of these known species are closely related on the basis of DNA characteristics such as base composition and thermal denaturation profiles of major DNA components. Minor components of ascospore DNA was, however, only 5-7% of total DNA instead of 15-20% minor component DNA shown by mycelial DNA. Species belonging to same group were not distinguishable morphologically, but all of these species were distinguishable by DNA:DNA homology studies. Greater DNA homology was noticed between DNAs of heterothallic species and DNAs of pseudohomothallic species than DNA of true homothallic species. Difference on DNA-nucleotide sequences among homothallic species was very little. Pseudo-homothallic species N. tetrasperma was found to be distinctly different from homothallic species but closer to heterothallic species based on such studies.

Base Sequence↗
PubMed2004

Sensitivity analyses of woody species exposed to air pollution based on ecophysiological measurements.

GOAL, SCOPE AND BACKGROUND: Air pollution has been of a major problem in the Pearl River Delta of south China, particularly during the last two decades. Emissions of air pollutants from industries have already led to damages in natural communities and environments in a wide range of the Delta area. Leaf parameters such as chlorophyll fluorescence, leaf area (LA), dry weight (DW) and leaf mass per area (LMA) had once been used as specific indexes of environmental stress. This study aims to determine in situ if the daily variation of chlorophyll fluorescence and other ecophysiological parameters in five seedlings of three woody species, Ilex rotunda, Ficus microcarpa and Machilus chinensis, could be used alone or in combination with other measurements for sensitivity indexes to make diagnoses under air pollution stress and, hence, to choose the correct tree species for urban afforestation in the Delta area. METHODS: Five seedlings of each species were transplanted in pot containers after their acclimation under shadowing conditions. Chlorophyll fluorescence measurements were made in situ by a portable fluorometer (OS-30, Opti-sciences, U.S.A). Ten random samples of leaves were picked from each species for LA measurements by area-meter (CI-203, CID, Inc., U.S.A). DW was determined after the leaf samples were dried to a constant weight at 65 degrees C. LMA was calculated as the ratio of DW/LA. Leaf N content was analyzed according to the Kjeldhal method, and the extraction of pigments was carried out according Lin et al. RESULTS AND DISCUSSION: The daily mean Fv/Fm (Fv is the variable fluorescence and Fm is the maximum fluorescence) analysis showed that Ilex rotunda and Ficus microcarpa were more highly resistant to pollution stress, followed by Machilus chinensis, implying that the efficiency of photosystem II in I. rotunda was less affected by air pollutants than the other two species. Little difference in daily change of Fv/Fm in I. rotunda between the polluted and the clean site was also observed. However, a relatively large variation of Fv/Fm appeared in the other two species, particularly in M. chinensis, suggesting that they were more sensitive to air pollutants than I. rotunda. The mean LA was reduced for all species growing at the polluted site. The mean LMA for all species exceeded the sclerophylly threshold given by Cowling and Campbell and increased for those under pollution stress, which could be explained as one of the acclimation strategies for plants to air pollution stress. Little difference in leaf chlorophyll content was observed in F. microcarpa and M. chinensis, while remarkable differences were found in I. rotunda growing at the polluted and the clean site. Content of leaf carotenoids was largely reduced in I. rotunda growing at the polluted site, but increased in F. microcarpa and M. chinensis, compared with plants growing at the clean site. Plants growing at the clean site had a lower leaf N content than those growing at the polluted site. In addition, species with a higher resistance to pollution stress showed less difference in leaf N content than those sensitive species. CONCLUSION: Based on Fv/Fm measurements of the three woody species, I. rotunda showed the highest resistance to air pollutants from ceramic industries, followed by F. microcarpa. M. chinensis was the most sensitive species to air pollution, had lowest capacities to cope with the air pollution stress, which was consistent with visual injury symptoms observed in the crown profiles of plants at the polluted site. Fv/Fm, LAM, LA, leaf pigments and N content could be used alone or in combination to diagnose the extent of the physiological injury. The ratio of Fv/Fm, however, was the best and most effective parameter. RECOMMENDATION AND OUTLOOK: Tree species which have higher air-pollutant resistance, as diagnosed by such ecophysiological parameters, should be considered first and planted widely for urban afforestation or forest regeneration in areas where the forest was seriously degraded or forest health was markedly effected by the same kind of air pollutants.

Air Pollutants↗
PubMed2003

The leaf size-twig size spectrum and its relationship to other important spectra of variation among species.

There is a spectrum from species with narrow, frequently branched twigs carrying small leaves and other appendages, to species with thick twigs carrying large leaves and appendages. Here we investigate the allometry of this spectrum and its relationship to two other important spectra of ecological variation between species, the seed mass-seed output spectrum and the specific leaf area-leaf lifespan spectrum. Our main dataset covered 33 woody dicotyledonous species in sclerophyll fire-prone vegetation on low nutrient soil at 1,200 mm annual rainfall near Sydney, Australia. These were phylogenetically selected to contribute 32 evolutionary divergences. Two smaller datasets, from 390 mm annual rainfall, were also examined to assess generality of cross-species patterns. There was two to three orders of magnitude variation in twig cross-sectional area, individual leaf size and total leaf area supported on a twig across the study species. As expected, species with thicker twigs had larger leaves and branched less often than species with thin twigs. Total leaf area supported on a twig was mainly driven by leaf size rather than by the number of leaves. Total leaf area was strongly correlated with twig cross-section area, both across present-day species and across evolutionary divergences. The common log-log slope of 1.45 was significantly steeper than 1. Thus on average, species with tenfold larger leaves supported about threefold more leaf area per twig cross-section, which must have considerable implications for other aspects of water relations. Species at the low rainfall site on loamy sand supported about half as much leaf area, at a given twig cross-section, as species at the low rainfall site on light clay, or at the high rainfall site. Within sites, leaf and twig size were positively correlated with seed mass, and negatively correlated with specific leaf area. Identifying and understanding leading spectra of ecological variation among species is an important challenge for plant ecology. The seed mass-seed output and specific leaf area-leaf lifespan spectra are each underpinned by a single, comprehensible trade-off and their consequences are fairly well understood. The leaf-size-twig-size spectrum has obvious consequences for the texture of canopies, but we are only just beginning to understand the costs and benefits of large versus small leaf and twig size.

Analysis of Variance↗
PubMed2006

Heat-induced hormesis in longevity of two sibling Drosophila species.

Previous work showed that mild-heat stress induces longevity hormesis in a model organism, D. melanogaster. Here we compared the possible heat-induced hormesis in longevity of other species of Drosophila, D. buzzatii and its sibling species D. koepferae, in a single-sex environment. Possible correlations between longevity and heat-stress resistance were also tested by measuring longevity, heat-knockdown resistance and the heat-induced Hsp70 expression for each species in a common environment. D. buzzatii was longer lived than D. koepferae at benign temperature. Knockdown resistance to heat stress was positively correlated to longevity within species. However, the shorter-lived species was more resistant to knockdown by heat stress than the longer-lived species. The heat-induced Hsp70 expression was similar between species. A heat-shock treatment (37 degrees C for 1 h at 4 days of age) extended mean longevity in the longer lived species but not in the shorter lived species. In D. koepferae, the demographic rate of senescence decreased but the baseline mortality rate increased by heat-shock, resulting in no extension of mean longevity. Sympatric populations of closely related species can be differentially sensitive to temperature and exhibit different patterns of 37 degrees C-induced hormesis in demographic senescence and longevity. The results also show that positive correlations between stress resistance and life span within species can shift in sign across closely related species. Finally, this study shows that heat-induced hormesis in longevity can be found across different Drosophila species, as hormetic effects are not limited to the previously studied D. melanogaster.

Aging↗
PubMed2003

Quantifying the species-specificity in genomic signatures, synonymous codon choice, amino acid usage and G+C content.

Each prokaryote has a unique genomic signature as evidenced by a set of species-specific frequencies of short oligonucleotides. With respect to genomic signatures a bacterial genome is homogenous and the variation within a genome is smaller than the variations between genomes of different species. This study quantifies the species-specificity of genomic signatures in the complete genomes of 57 prokaryotes. The species-specificity in the genomic signature was related to the quantification of other sequence biases, such as G+C content, synonymous codon choice and amino acid usage. The results confirm that the genomic signature is genome-wide with high species-specificity in both coding and non-coding regions. In coding regions the species-specific bias in synonymous codon choice was comparable to the genomic signature, while the bias in amino acid usage only captured about 50% of the species-specific bias in the genomic signature. A correlation between the species-specificity in synonymous codon choice and amino acid usage was identified, in which proteins with species-specific amino acid usage were also coded with species-specific synonymous codon choice. However, we demonstrated that the G+C content captures only approximately 40% of the species-specificity in the genomic signature, and is insufficient to explain the species specificity in the non-coding regions. Thus, the species-specific bias in non-coding regions remains largely unknown. Further, we compared the genomic signature in relation to phylogenetic distance. This was performed in order to illustrate the feasibility of a hierarchical classification scheme in future applications of the described classification methodology in screening for horizontal gene transfer and biodiversity studies.

Amino Acids↗
PubMed2003

PCR-based identification of common dermatophyte species using primer sets specific for the DNA topoisomerase II genes.

BACKGROUND: We have determined nucleotide sequences of the DNA topoisomerase II genes of the dermatophyte species, and conducted a PCR-based identification system using species-specific primers for the nucleotide sequences. OBJECTIVE: To identify the major dermatophytes, Trichophyton rubrum, T. mentagrophytes, T. violaceum, M. gypseum, M. canis and E. floccosum, by PCR amplifications at the species level, without determining the nucleotide sequence. METHODS: For PCR-based identification of the major dermatophyte species, a common primer set (dPsD1) for these species and species-specific primer sets (PsT and PsME) for each species were designed based on the genomic sequences of the DNA topoisomerase II genes of the dermatophytes, and tested for their specificities in PCR amplifications. The method consisted of amplification of the genomic DNA topoisomerase II gene by the common primer set, followed by a second PCR with the primer sets consisting of species-specific primers for each dermatophyte species. RESULTS: Using dPsD1, a DNA fragment of 3390 bp was amplified from the genomic DNA of all the dermatophyte species. In the subsequent nested PCR using species-specific primer sets (PsT and PsME), both sets amplified unique sizes of PCR products, all of which corresponded to a species of the dermatophytes even in the presence of other fungal DNA. CONCLUSION: We demonstrate that the PCR-based identification targeting the DNA topoisomerase II gene is rapid and simple, and is available as a tool for the identification of the major dermatophyte species.

Arthrodermataceae↗