Resolution of inter and intra-species relationships of the West Indian fruit fly Anastrepha obliqua.

The West Indian fruit fly, Anastrepha obliqua (Diptera: Tephritidae), is an economically important pest that inhabits areas of South and Central America, Mexico and the Caribbean with occasional infestations in the southern United States. We examine intra-specific relationships within A. obliqua as well as interspecific relationships to other Anastrepha species using a multi-locus data set comprising nine loci (seven nuclear, two mitochondrial) with 105 operational taxonomic units. The results based on a concatenated set of nuclear loci strongly support the monophyly of A. obliqua and most of the other species previously identified by morphology. A split between Peruvian A. obliqua samples and those from other locations was also identified. These results contrast with prior findings of relationships within A. obliqua based on mitochondrial data, as we found a marked discrepancy between nuclear and mitochondrial loci. These analyses suggest that introgression, particularly between A. obliqua and fraterculus species, may be one explanation for the discrepancy and the high mitochondrial diversity reported for A. obliqua could be the result of incomplete lineage sorting.

Development of a ribosomal DNA ITS2 marker for the identification of the thrips, Scirtothrips dorsalis.

The thrips Scirtothrips dorsalis Hood (Thysanoptera: Thripidae) is an invasive pest that poses a significant economical threat to U.S. agriculture and trade. In this study, DNA sequence data and polymerase chain reaction (PCR) were utilized to develop a molecular diagnostic marker for S. dorsalis. The DNA sequence variation from the internal transcribed spacer 2 (ITS2) region of nuclear ribosomal DNA (rDNA) was analyzed from various thrips species, including S. dorsalis. A primer set and polymerase chain reaction cycling parameters were designed for the amplification of a single marker fragment of S. dorsalis ITS2 rDNA. Specificity tests performed on ten thrips species, efficacy tests performed on fifteen S. dorsalis populations, and tests on primer sensitivity and robustness all demonstrated the diagnostic utility of this marker. This diagnostic PCR assay provides a quick, simple, and reliable molecular technique to be used in the identification of S. dorsalis.

Genetic variation and population structure of Diaphorina citri using cytochrome oxidase I sequencing.

Citrus greening disease, or huanglongbing (HLB), is currently one of the most devastating diseases of citrus. The bacteria thought to be responsible for the disease, Candidatus Liberibacter asiaticus impact the majority of commercial citrus species worldwide. These bacteria are transmitted by the Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, which is now found in most citrus growing regions. With no known cure, ACP-vectored HLB is responsible for significant economic losses to the global citrus industry. A better understanding of the global genetic diversity of D. citri would improve current and future pest management and mitigation programs. To assess the genetic diversity of D. citri in worldwide collections, a total of 1,108 sequences belonging to ACP gathered from 27 countries in the Americas, the Caribbean, Southeast and Southwest Asia were examined for the study. 883 D. citri came from 98 locations in 18 different countries, and were sequenced using a 678bp fragment of the mitochondrial cytochrome oxidase I (COI) gene. Additionally, 225 previously-reported D. citri COI sequences, were also included in our analysis. Analyses revealed 28 haplotypes and a low genetic diversity. This is in accordance with previous reports on the little diversity of D. citri in worldwide populations. Our analyses reveal population structure with 21 haplotypes showing geographic association, increasing the resolution for the source estimation of ACP. This study reveals the distribution of haplotypes observed in different geographic regions and likely geographic sources for D. citri introductions.