Seasonal population dynamics and a role as natural vector of Leucocytozoon of black fly, Simulium chumpornense Takaoka & Kuvangkadilok.

The black fly, Simulium chumpornense Takaoka & Kuvangkadilok, is suspected to be a natural vector of Leucocytozoon. In this study, seasonal variation in abundance of the adult fly and molecular detection of Leucocytozoon in S. chumpornense and in domestic chicken was investigated in northeastern Thailand. A total of 10,416 female adults were obtained by monthly collection for one year at six sampling sites. There was a peak of abundance in the dry season (March - May) when more than 74% of the specimens were collected. An increased number of suitable habitats for immature stages during the dry season is potentially a factor driving dry season abundance. Molecular genetic investigations revealed that S. chumpornense harbored the infectious stage of Leucocytozoon sp. indicating that it is a natural vector of this parasite. Blood smear screening for the parasite in domestic chickens found a considerable prevalence (52%) of Leucocytozoon spp. infections. The cytochrome b sequences of this parasite in domestic chickens comprised two lineages. One lineage was closely related to Leucocytozoon sp. found in S. chumpornense and another matched with L. schoutedeni. Therefore, S. chumpornense is a vector of Leucocytozoon sp. while L. schoutedeni is possibly transmitted by other ornithophilic black fly species.

DNA barcoding of fruit flies (Diptera: Tephritidae) in Thailand: ambiguity, misidentification and cryptic diversity.

Fruit flies (Diptera: Tephritidae) are significant insect pests of many commercially important fruits and vegetables. Therefore, rapid and accurate species identification methods are required for the regulation, management and quarantine of these pests. In this study, we examined the efficiency of mitochondrial cytochrome c oxidase I sequences for species identification of fruit flies in Thailand. Data analyses based on 42 fruit fly taxa revealed moderate performance of this genetic marker. There were 14 taxa that have no barcode gap and thus could not be identified unambiguously to species by this methodology. Taxonomic uncertainty, inadequate variation of the marker and misidentifications of specimens deposited in the public database are the most likely factors explaining unsuccessful identification. DNA barcodes also revealed cryptic diversity in five taxa (Bactrocera caudata, B. tuberculata, B. infesta, Zeugodacus isolatus, Carpomya vesuviana). These species require further taxonomic investigation of if they are different cryptic taxa or are indications of geographic structuring of within single species.

Population genetics of the solanum fruit fly, Bactrocera latifrons (Hendel) (Diptera: Tephritidae).

The solanum fruit fly, Bactrocera latifrons (Hendel), is an important pest species of commercial plants in the family Solanaceae. In this study, the population genetic structure of B. latifrons was investigated using mitochondrial cytochrome c oxidase I sequences. A mitochondrial DNA haplotype network revealed no major genetic break, but haplotypes from recently invaded areas in Japan, Tanzania, and Kenya were genetically divergent. The overall haplotype network is approximately star-shaped, characteristic of recent demographic expansion of populations. This is also supported by large negative values of neutrality tests. Despite the overall pattern of recent population history, genetic structure analysis revealed considerable genetic structuring with 33% of pairwise comparisons being significantly different. Populations that were genetically different from the others usually possess low genetic diversity, suggesting that genetic drift is potentially a factor driving genetic differentiation. Local extinction and recolonization processes related to the availability of host plants are most likely responsible for a founder effect and subsequent genetic drift in a population.

DNA barcode variability and host plant usage of fruit flies (Diptera: Tephritidae) in Thailand.

The objectives of this study were to examine the genetic variation in fruit flies (Diptera: Tephritidae) in Thailand and to test the efficiency of the mitochondrial cytochrome c oxidase subunit I (COI) barcoding region for species-level identification. Twelve fruit fly species were collected from 24 host plant species of 13 families. The number of host plant species for each fruit fly species ranged between 1 and 11, with Bactrocera correcta found in the most diverse host plants. A total of 123 COI sequences were obtained from these fruit fly species. Sequences from the NCBI database were also included, for a total of 17 species analyzed. DNA barcoding identification analysis based on the best close match method revealed a good performance, with 94.4% of specimens correctly identified. However, many specimens (3.6%) had ambiguous identification, mostly due to intra- and interspecific overlap between members of the B. dorsalis complex. A phylogenetic tree based on the mitochondrial barcode sequences indicated that all species, except for the members of the B. dorsalis complex, were monophyletic with strong support. Our work supports recent calls for synonymization of these species. Divergent lineages were observed within B. correcta and B. tuberculata, and this suggested that these species need further taxonomic reexamination.