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V Baimai

Publications and source records attributed to V Baimai.

At least 19 recordsLinked to original sources
PubMed2006

Closely related Wolbachia strains within the pumpkin arthropod community and the potential for horizontal transmission via the plant.

Phylogenetic studies have implicated frequent horizontal transmission of Wolbachia among arthropod host lineages. However, the ecological routes for such lateral transfer are poorly known. We surveyed the species of two arthropod communities, one on pumpkin and the other on loofah plants, for Wolbachia, constructed wsp gene phylogenies of those Wolbachia strains found to infect community members, and established ecological links among infected members. Four taxonomically diverse insects in the pumpkin arthropod community contained very closely related Wolbachia wsp sequences (<1.5% divergence by Kimura-2-parameter distances). These insects, namely, the whitefly Bemisia tabaci, the planthopper Nisia nervosa, the flea beetle Phyllotreta sp., and the fleahopper Halticus minutus, were all collected from pumpkin leaves. They were ecologically linked through feeding on the same leaf substrate. Unlike other infected leaf insects, the whitefly population appeared to have a permanent breeding relationship with pumpkin plants, and high and stable, but not fixed, monthly Wolbachia infection rates. Our findings suggest potential roles for the plant in Wolbachia transmission and for whiteflies in being an infection source for other pumpkin leaf-feeding insects.

Animals↗
PubMed2006

Bacteriophage WO-B and Wolbachia in natural mosquito hosts: infection incidence, transmission mode and relative density.

Bacteriophages of Wolbachia bacteria have been proposed as a potential transformation tool for genetically modifying mosquito vectors. In this study, we report the presence of the WO-B class of Wolbachia-associated phages among natural populations of several mosquito hosts. Eighty-eight percent (22/25) of Wolbachia-infected mosquito species surveyed were found to contain WO-B phages. WO-B phage orf7 sequence analysis suggested that a single strain of WO-B phage was found in most singly (23/24) or doubly (1/1) Wolbachia-infected mosquitoes. However, the single Wolbachia strain infecting Aedes perplexus was found to harbour at least two different WO-B phages. Phylogenetic analysis suggested that horizontal transmission of WO-B phages has occurred on an evolutionary scale between the Wolbachia residing in mosquitoes. On an ecological scale, a low trend of co-transmission occurred among specific WO-B phages within Wolbachia of each mosquito species. Assessment of the density of WO-B phage by real-time quantitative polymerase chain reaction (RTQ-PCR) revealed an average relative density of 7.76 x 10(5)+/- 1.61 x 10(5) orf7 copies per individual mosquito for a single Wolbachia strain infecting mosquitoes, but a threefold higher density in the doubly Wolbachia-infected Aedes albopictus. However, the average combined density of WO-B phage(s) did not correlate with that of their Wolbachia hosts, which varied in different mosquito species. We also confirmed the presence of WO-B-like virus particles in the laboratory colony of Ae. albopictus (KLPP) morphologically, by transmission electron microscopy (TEM). The viral-like particles were detected after purification and filtration of Ae. albopictus ovary extract, suggesting that at least one WO-B-like phage is active (temperate) within the Wolbachia of this mosquito vector. Nevertheless, the idea of utilizing these bacteriophages as transformation vectors still needs more investigation and is likely to be unfeasible.

Animals↗
PubMed2002

Host age effect and expression of cytoplasmic incompatibility in field populations of Wolbachia-superinfected Aedes albopictus.

The Asian tiger mosquito, Aedes albopictus (Skuse), is a known vector of dengue in South America and Southeast Asia. It is naturally superinfected with two strains of Wolbachia endosymbiont that are able to induce cytoplasmic incompatibility (CI). In this paper, we report the strength of CI expression in crosses involving field-caught males. CI expression was found to be very strong in all crosses between field males and laboratory-reared uninfected or wAlbA infected young females. In addition, crossing experiments with laboratory colonies showed that aged super-infected males could express strong CI when mated with young uninfected or wAlbA infected females. These results provide additional evidence that the CI properties of Wolbachia infecting Aedes albopictus are well suited for applied strategies that seek to utilise Wolbachia for host population modification.

Aedes↗
PubMed2002

SCAR markers and multiplex PCR-based identification of isomorphic species in the Anopheles dirus complex in Southeast Asia.

The Anopheles dirus Peyton & Harrison complex of mosquitoes (Diptera: Culicidae) comprises seven known species, including important malaria vectors in Southeast Asia. Specific identification of each species of the complex, which cannot be distinguished using morphological characters, is crucial for understanding vector ecology and implementing effective control measures. Derived from individual random amplified polymorphic DNA (RAPD) markers, sequence characterized amplified regions (SCAR) were analysed for the design of specific paired-primers. Combination of six SCAR primers resulted in the development of a simple, robust, single multiplex PCR able to identify three important malaria vectors among the four most common species (A, B, C, D) of the complex: species A from several Southeast Asian countries, species B from Perlis, Malaysia, and species C and D from Thailand.

Animals↗
PubMed2001

A multiplex PCR-based method derived from random amplified polymorphic DNA (RAPD) markers for the identification of species of the Anopheles minimus group in Southeast Asia.

Effective control of Anopheles minimus s.l., an important malaria vector in Southeast Asia, is based on the accurate identification of species within An. minimus complex, which cannot be distinguished using morphological characters. Derived from individual random amplified polymorphic DNA markers, sequence characterized amplified regions were analysed for the design of species-specific paired-primers. Combination of these primers resulted in the development of a simple, robust multiplex PCR able to identify both species An. minimus A and C belonging to the complex, hybrids AC, and three sympatric and closely related species, An. aconitus, An. pampanai and An. varuna. Hybrids AC do not possess alleles of both parents but exhibit novel adaptive potentials resulting from recombination among parental genes leading to hybrizyme.

Animals↗
PubMed2001

Genetic population structure and introgression in Anopheles dirus mosquitoes in South-east Asia.

Genetic structure and species relationships were studied in three closely related mosquito species, Anopheles dirus A, C and D in Thailand using 11 microsatellite loci and compared with previous mitochondrial DNA (mtDNA) data on the same populations. All three species were well differentiated from each other at the microsatellite loci. Given the almost complete absence of mtDNA differentiation between An. dirus A and D, this endorses the previous suggestion of mtDNA introgression between these species. The high degree of differentiation between the northern and southern population of An. dirus C (RST = 0.401), in agreement with mtDNA data, is suggestive of incipient species. The lack of genetic structure indicated by microsatellites in four populations of An. dirus A across northern Thailand also concurs with mtDNA data. However, in An. dirus D a limited but significant level of structure was detected by microsatellites over ~400 km in northern Thailand, whereas the mtDNA detected no population differentiation over a much larger area (>1200 km). There is prior evidence for population expansion in the mtDNA. If this is due to a selective sweep originating in An. dirus D, the microsatellite data may indicate greater barriers to gene flow within An. dirus D than in species A. Alternatively, there may have been historical introgression of mtDNA and subsequent demographic expansion which occurred first in An. dirus D so enabling it to accumulate some population differentiation. In the latter case the lack of migration-drift equilibrium precludes the inference of absolute or relative values of gene flow in An. dirus A and D.

Animals↗
PubMed2000

Distribution of the transposable element mariner in anopheline mosquitoes.

We have surveyed the distribution of the transposable element mariner using PCR in 23 species of Anopheles mosquitoes, including all of the most important vectors of malaria in South-east Asia. Sequencing of the nine positive species revealed elements from the irritans, mauritiana and mellifera subfamilies. These are the first data showing the presence of three subfamilies of mariners in anophelines. The elements we encountered are likely to be inactive, based on the presence of multiple stop codons and/or frameshifts.

Animals↗
PubMed2000

Distribution and diversity of Wolbachia infections in Southeast Asian mosquitoes (Diptera: Culicidae).

Wolbachia are a group of intracellular inherited bacteria that infect a wide range of arthropods. They are associated with a variety of reproductive alterations in their hosts, the best known being cytoplasmic incompatability. The Wolbachia pipientis assemblage has been divided into two major groups (A and B) and 12 subgroups. We report herein the first systematic survey of Wolbachia in mosquitoes, and the first survey classifying Wolbachia infections by subgroup. Wolbachia were detected in 28.1% of 89 wild-caught mosquito species, based on a polymerase chain reaction assay using ftsZ and wsp gene primers. Infections were found in all major disease vector genera except Anopheles. Nine of the 12 Wolbachia subgroups were represented. Group B Wolbachia strains showed more phylogenetic concordance with their host taxa than group A strains. Of the 25 positive mosquito species, five were superinfected with group A bacteria strains (AA), eight were superinfected with A and B strains (AB), and one was superinfected with group B strains (BB). The widespread distribution of Wolbachia among mosquito species further supports their potential importance in the genetic control of disease vectors.

Aedes↗
PubMed2000

Population structure and population history of Anopheles dirus mosquitoes in Southeast Asia.

Separating the confounding effects of long-term population history from gene flow can be difficult. Here, we address the question of what inferences about gene flow can be made from mitochondrial sequence data in three closely related species of mosquitoes, Anopheles dirus species A, C, and D, from southeast Asia. A total of 84 sequences of 923 bp of the mitochondrial cytochrome oxidase I gene were obtained from 14 populations in Thailand, Myanmar, and Bangladesh. The genealogy of sequences obtained from two populations of AN: dirus C indicates no contemporary gene flow between them. The F(ST) value of 0.421 therefore probably represents a recent common history, perhaps involving colonization events. Anopheles dirus A and D are parapatric, yet no differentiation was seen either within or between species. The starlike genealogy of their haplotypes, smooth unimodal mismatch distributions, and excess of low frequency mutations indicate population expansion in An. dirus A and D. This, rather than widespread gene flow, explains their low within-species F(ST) values (0.018 and 0.022). The greater genetic diversity of An. dirus D suggests that expansion occurred first in species D and subsequently in species A. The current geographical separation and low hybrid fitness of these species also argue against ongoing interspecific gene flow. They suggest instead either historical introgression of mtDNA from An. dirus D into species A followed by independent range expansions, or a selective sweep of mtDNA that originated in An. dirus D. While not excluding contemporary gene flow, historical population processes are sufficient to explain the data in An. dirus A and D. The genealogical relationships between haplotypes could not be used to make inferences of gene flow because of extensive homoplasy due to hypervariable sites and possibly also recombination. However, it is concluded that this approach, rather than the use of fixation indices, is required in the future to understand contemporary gene flow in these mosquitoes. The implications of these results for understanding gene flow in another important and comparable group of malaria vector mosquitoes in Africa, the An. gambiae complex, are also discussed.

Animals↗
PubMed1999

Protein polymorphism in natural populations of Diachasmimorpha longicaudata (Hymenoptera: Braconidae) in Thailand.

Diachasmimorpha longicaudata (Ashmead) is a larval parasitoid of tephritid flies and is widely used as a classical biological control agent. We have used allozyme electrophoresis to evaluate the genetic relationships of six populations of D. longicaudata in Thailand. Twelve loci were examined of which 11 were polymorphic in at least some populations, especially that of Nakornratchasima. We observed a complete lack of heterozygotes for seven of the 10 polymorphic loci in the Nakornratchisima female population, and a significant deficiency of heterozygotes at a further two loci. We discuss possible hypotheses for these findings in light of the haplo-diploid sex determination system of these wasps.

Animals↗
PubMed1999

Genetic differentiation in Thai populations of the rare species Afgekia sericea Craib (Leguminosae) revealed by RAPDPCR assays.

Genetic diversity within and among populations was investigated using RAPD-PCR assays in a rare species, Afgekia sericea Craib. Two hundred and sixty-nine individuals were sampled from nine geographically isolated populations from northeastern Thailand. This study includes 73 RAPD markers. Within population polymorphism as measured by percentage of polymorphic RAPDs, varied between 38.4% and 60.3%. Genetic variability was measured using Shannon's information index and partitioned into between- and within-population components. Overall, genetic variation among A. sericea populations was high (H(sp)-H(pop))/H(sp)=48.2%. The genetic diversity for the species (H(sp)) was 43.2%. Mean of within-population values (H(pop)) for all populations was 0.224. The total genetic diversity was explained by high variation among populations (mean Gst=0.426), which is consistent with low gene flow among populations (Nm=0.35). High between-population genetic variation observed in this study could be explained by limited migration through seed and/or pollen dispersal among populations. Conservation strategies of A. sericea are discussed in the context of these results.

Journal Article↗
PubMed1999

Identification of five species of the Anopheles dirus complex from Thailand, using allele-specific polymerase chain reaction.

The Anopheles dirus complex of mosquitoes contains some of the most important vectors of malaria in Southeast Asia. To distinguish five species of the complex that occur in Thailand, a method using the polymerase chain reaction (PCR) was developed. The method utilizes allele-specific amplification to detect fixed differences between the species in the DNA sequence of the ribosomal DNA internal transcribed spacer 2. Primers were designed to amplify fragments of diagnostic length from the DNA of the different species. The method was tested on 179 mosquitoes of the An. dirus complex from many parts of Thailand and shown to be effective. Every specimen was unambiguously identified as species A, B, C, D or F (i.e. An. dirus s.s. species B, C, D or An. nemophilous, respectively) by the PCR method, with confirmation of 58/61 identifications from polytene chromosome characteristics. For the other three specimens (3/44 from Kanchanaburi 5 locality), there was disagreement between the PCR and chromosomal methods of species identification (probably due to errors in the chromosomal identifications). Primers can be combined in a single PCR reaction providing a rapid, sensitive and straightforward method of species identification. Only small quantities of DNA are required, leaving most of the mosquito to be used for other analyses.

Alleles↗
PubMed1999

Isozyme evidence for three sibling species in the Anopheles sundaicus complex from Indonesia.

Electrophoretic studies of isoenzymes in three chromosomally distinct forms (A, B and C) of the mosquito Anopheles sundaicus Theobald (Diptera: Culiciae) were undertaken on wild samples collected from six geographically isolated populations in Indonesia. Analyses of 12 enzyme systems comprising 15 loci revealed significant allelic variations, genetic polymorphism, within and among the populations of the An. sundaicus complex. Phylogenetic dendrograms produced by analysis using the Biosys-1 program based on UPGMA methods show that all the populations of form A fall into one cluster, which is closely related to the form C cluster, whereas the populations of form B belong to a more distinct cluster. Allelic frequency and Wright's F statistics of Mpi (mannose phosphate isomerase) are sufficient to identify individuals of each cytological form. This isozyme data correlates with our previous cytological evidence for the existence of three isomorphic species within the taxon An. sundaicus in Indonesia. These three species of the An. sundaicus complex were found together sympatrically at one locality, Asahan in North Sumatra.

Animals↗
PubMed1996

Heterochromatin variation in chromosome X in a natural population of Anopheles willmori (Diptera: Culicidae) of Thailand.

Among the eight families of Anopheles willmori derived from individual wild-caught females collected from Chiangmai Province (northern Thailand) and examined, four isofemale lines showed variation in the X chromosome, including the normal X1 and three aberrant types (X3, X4 and XL). It is postulated that these different types of X chromosomes could have arisen as a result of spontaneous chromosomal rearrangements involving tandem translocation and paracentric inversion followed by acquisition of constitutive heterochromatin. Such rare events of chromosomal changes have become established in the natural population of An. willmori in northern Thailand.

Animals↗
PubMed1996

Metaphase karyotypes of Anopheles of Thailand and Southeast Asia: V. The Myzomyia Series, subgenus Cellia (Diptera:Culicidae).

Metaphase karyotypes of 9 species of the Myzomyia Series show intra- and interspecific differences based on quantitative variation and distribution of constitutive heterochromatin in the sex chromosomes or the centromeric regions of the autosome pairs or both. Anopheles jeyporiensis and Anopheles aconitus each exhibit 4 forms of mitotic karyotypes, which may reflect interspecific differences within each taxon. The well-defined genetic species within the Anopheles minimus and the Anopheles culcifacies complexes clearly exhibit distinctive metaphase karyotypes that can be used as diagnostic characters for separating these sibling species, which are difficult to identify by morphological criteria alone. Our analysis on metaphase karyotypes of Anopheles pampanai, Anopheles varuna, and Anopheles flavirostris also confirms their morphological identification based on heterochromatin differences in the sex chromosomes and autosome 2.

Animals↗
PubMed1996

Metaphase karyotypes of Anopheles of Thailand and Southeast Asia. VI. The Pyretophorus and the Neomyzomyia series, subgenus Cellia (Diptera:Culicidae).

A total of 6 species of the Pyretophorus (4 species) and Neomyzomyia (2 species) series of the subgenus Cellia of Anopheles were used for metaphase karyotype analysis. Anopheles subpictus and An. vagus exhibit 4 and 2 forms of mitotic karyotypes, respectively, which are attributable to different types of Y chromosomes. Such distinctive mitotic chromosomes may reflect interspecies differences within each of these 2 taxa. Two distinct species, An. indefinitus and An. sundaicus, show similar metaphase karyotypes, particularly with regard to the size and shape of the sex chromosomes. Likewise, An. tessellatus and An. kochi, which are distinct species of the Neomyzomyia Series, also have metaphase karyotypes that resemble each other. They exhibit a typical feature of telocentric sex chromosomes resembling those of the An. dirus complex and the other species of the Leucosphyrus Group. Like the other cases of the Oriental Anopheles, heterochromatin has played a significant role in chromosome evolution of the 6 species.

Animals↗
PubMed1995

Metaphase karyotypes of fruit flies of Thailand. I. Five sibling species of the Bactrocera dorsalis complex.

Natural populations of fruit flies of the Bactrocera dorsalis complex exhibit chromosomal variation based on differences in the amount and distribution of constitutive heterochromatin in the centromeric regions of the autosomes and the sex chromosomes. The chromosomal variation, coupled with differences in external morphology and host plant specific preferences, strongly suggest the existence of 5 closely related species within the B. dorsalis complex that have provisionally been designated B. dorsalis species B, C, D, and E in contrast with B. dorsalis s.s. (species A). Analysis of heterochromatin in autosomes and sex chromosomes has revealed 4 distinct groups of mitotic karyotypes. Bactrocera dorsalis is the only representative of Group I, which is characterized by the typical metacentric X chromosome and major blocks of centromeric heterochromatin in autosomes 5 and 6. Group 2 consists of species B and C, which show prominent landmarks of pericentric heterochromatin in all autosomes and in the X chromosome. Group 3 comprises species D, which is characterized by conspicuous blocks of pericentric heterochromatin in all autosomes but the long arm of the subtelocentric X chromosome is euchromatic and lacks a major portion of centromeric heterochromatin. Species E belongs to Group 4, which differs from Group 3 in having major blocks of heterochromatin at the distal portion of the X chromosome in addition to the prominent landmarks of pericentric heterochromatin in all autosomes. Chromosomal evolution among closely related species within the B. dorsalis complex clearly involves the presence or absence of constitutive heterochromatin in the centromeric regions of autosomes as well as in the X chromosome.

Animals↗