Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/2011
Publication Date: 12/1/2011
Citation: Kumar, V., Seal, D.R., Schuster, D.J., McKenzie, C.L., Osborne, L., Maruniak, J., Zhang, S. 2011. Scirtothrips dorsalis (Thysanoptera: Thripidae): Scanning electron micrographs of key taxonomic traits and a preliminary morphometric analysis of the general morphology of populations of different continents. Florida Entomologist. 94(4):941:955. Available: http://www.bione.org/doi/full/10.1653/024.094.0431 Interpretive Summary: The exotic thrips, Scirthothrips dorsalis (Hood), has become established in Florida and is a real threat to the fruit, ornamental and vegetable industries due to its devastating feeding damage that can result in plant death and its potential to spread viral diseases to its host plants. Rapid and accurate identification of this exotic pest is essential to implementing effective plant quarantine and biological control initiatives. Traditional taxonomy of this species is difficult because morphological traits vary widely. By using traditional taxonomic keys, specimens of thrips can be assigned to a particular genus, but because of intraspecific morphological variation, the identification of the species of many specimens requires great expertise. Comparison of the morphometric traits of S. dorsalis populations from five different geographic regions where used to study the variation of this species. Fourteen morphological traits of ten specimens from each of five geographic regions were quantified by measuring the lengths of the body, antennae, head, prothorax, mesothorax, metathorax, ovipositor, forewing and hind wing, and the widths of the head, abdomen, prothorax, mesothorax, and metathorax.
Technical Abstract: Scirtothrips dorsalis (Hood) is an emerging pest of numerous economically important vegetable and ornamental crops in Florida. Since its advent in 2005, it has rapidly dispersed across the state and is causing significant damage to horticultural and nursery production statewide. A comparison of morphometric traits of S. dorsalis populations from different geographical regions was used to study the morphological variation of this species. Specimens of S. dorsalis were obtained from five different geographical regions: New Delhi, India, Shizouka, Japan, St. Vincent, Negev, Israel and Florida, United States of America. Fourteen morphometric characters of each population were analyzed and compared among the five populations. No significant differences were observed between body lengths of the various S. dorsalis populations which ranged from 0.83 mm (Negev) to 0.98 mm (Florida). Data on the measurements of S. dorsalis from each region were also compared with a report from New Delhi, India (1976) to analyze any change in their body sizes during the last three decades. Apparently the mean body lengths of adults from each population are greater than the reported study (0.76 mm) with all other measurements being comparable. No significant differences were detected between antennal length, head length or width, prothorax length or width, and the lengths of the ovipositor, forewing and hindwing among any of the populations evaluated. However, the mesothorax and the metathorax length and width of the Japan population were significantly larger than the Florida population. The Japan population mesothorax width and metathorax length was also significantly larger than the Israel population. The population from St. Vincent metathorax and abdomen widths was significantly smaller than the Japan population. Together these measurements indicate that the Japan population was significantly larger than the other populations.