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United States Department of Agriculture

Agricultural Research Service

Related Topics

Research Project: Mite Systematics and Arthropod Diagnostics with Emphasis on Invasive Species

Location: Systematic Entomology

2011 Annual Report


1a.Objectives (from AD-416)
The long-term goal of this project is to produce systematic revisions of monophyletic groups of Acari that are important to U.S. agriculture and transfer this information to stakeholders, scientists, and the general public. The project will focus on the mite families Tenuipalpidae (flat mites) and Tuckerellidae (peacock mites) (both superfamily Tetranychoidea), which are of increasing importance on ornamentals and fruit crops in the U.S. Two flat mite genera, Brevipalpus and Raoiella, are affecting thousands of acres of citrus and palms, respectively, across the U.S. and worldwide; and several species of Brevipalpus are strongly linked with the transmission of serious plant viruses. The peacock mites (genus Tuckerella) cause damage to citrus, avocado, tea, and other ornamental and fruit tree crops. Despite their economic importance, these mite genera are in need of rigorous systematic revision, and the tools available for their identification need improvement. An additional goal is to contribute to the currently minimal understanding of the systematics and classification of these taxa through comparative morphological studies. Over the next 5 years the project will focus on the following objectives: (1) Develop accurate species concepts within mite groups using a holistic approach based on morphological and ecological data; (2) Determine and identify adventive species of mites; (3) Evaluate current taxonomic concepts of mites through discovery of new characters for species separation and subsequent systematic relationships; and (4) Process incoming and outgoing arthropod specimens and identifications, and maintain SELIS (Systematic Entomology Laboratory Identification Service), the on-line identification database about agriculturally important arthropods, for use in quarantine conservation, pest management, and other ARS research programs.


1b.Approach (from AD-416)
Morphological characters will be identified through the examination of specimens using dissecting, Differential Interference Contrast (DIC), Phase Contrast, Confocal microscopes and low temperature scanning electron microscopy (LT-SEM). The novel characters available with LT-SEM will be investigated and assessed using a minimum of 10 species from each genus, or more as time and resources permit. The validity of key characters for separating species and genera will be investigated across the family. As part of the data-gathering process, numerous techniques will be used to assess homology and variation in structural characteristics. Measurements and basic statistical data (i.e. range, mean) are often a part of this assessment. Characters will be scored as either discrete or continuous and ordered or unordered, and compiled into a data matrix for analysis. Analyses of the morphological data to construct hypotheses of evolutionary relationships will be conducted using PAUP and MrBayes. MrBayes for Bayesian analyses, and PAUP for parsimony analyses. Although the research will focus primarily on morphological and ecological characters, these data sets will be augmented with molecular data (COI, 18s, 28s, EF-1') obtained from collaborators at the University of Arkansas. Character information will include the external and internal morphology of mounted peacock mites, genus Tuckerella adults and immatures, combined with the molecular data. Identification tools will be developed for users to identify a specific organism among similar organisms and associate a name with that organism. This project will produce traditional dichotomous keys for this purpose, as well as electronic and/or interactive tools that facilitate identifications (e.g., LucID, DELTA). Throughout this project, an additional goal of curating (including remounting and relabeling where needed) and databasing the sections of the collection held in the U.S. National Mite Collection (USNMC) will be met. Mite specimens submitted to the Systematic Entomology Laboratory for identification will be prioritized primarily by importance of their impact, invasive behavior, the number of interceptions, and the commodity involved. The Taxonomic Services Unit is responsible for distributing arthropod specimens submitted for identification to the appropriate SEL research entomologists or collaborators. When the specialists have identified and added their identifications to SELIS, TSU generates a report which is sent to submitters. The TSU coordinates with APHIS, PPQ on a daily basis on various issues relating to identification of specimens intercepted at ports-of-entry or in domestic surveys, especially those specimens with URGENT priority from shipments being detained at ports of entry pending receipt of identification reports from SEL. This objective will result in more than 13,000 identifications (34,000 specimens/year), along with associated biological information, of arthropods annually to customers dependent upon these data for the exclusion of invasive species, assessing potential biological control agents, systematic and biological research, and in support of regulatory programs.


3.Progress Report
In FY 2011, scientists were able to study mites in the genus Brevipalpus which revealed a systematic controversy. The major mite species affecting the citrus production in the Americas, which is associated with some very important virus family (leprosis virus), was an obscure species that was wrongly synonymized with Brevipalpus phoenicis. We worked on the Raoiella genus and obtained samples from most of the countries affected by there presence; however, we are still waiting for material from Greece.

We developed a web-based key (Lucid key) for the flat mite family. The flat mite lucid key will need testing from the register users. We were able to collect and obtain Tueckerella and Tenuipalpidae material from Australia, Brazil and the U.S. A total of six publications addressing plant feeding mites, predator mites and mite morphology were published in refereed journals.

Began reseach on two LucID project for mites in the genus Raoiella and Brevipalpus intercepted at ports-of-entry or important in plant protection programs.

The project includes the preparation of specimens of important tenuipalpid mites (including species in the genus Brevipalpus and Raoiella) and prostigmatid mites (families Tarsonemidae, Eriophyidae and Tetranychidae) for scanning electron micrographs and key illustrations.


4.Accomplishments
1. Studies of plant feeding mites on economically important fruit trees, ornamental and crop plants provided new information for identification and classification. The red palm mite was identified as one of the major arthropod pest problems on palms. The red palm mite and relative species are able to affect several species of palms, eucalyptus and other fruit trees by directly feeding cross the specialized gas exchange cells (stomata) located on the leaflets or leaves. Discovery of these specialized feeding sites changes the way this mite can be controlled/managed and it potentially changes its current classification and host plant associations. The scarlet flat mite was previously considered one of the most important mite pest species affecting citrus in the world. However, by studying material from Europe, South America, Australia and the U.S. it was discovered that the mite has been misidentified and the most common species on citrus is another species of similar appearance. Since correct identification is essential before any control or management program can be implemented, this information is critical for farmers, quarantine specialists, extension agents, state and university researchers. Taxonomic Service Unit of the Systematic Entomology Laboratory processed and tracked insect specimens and identifications in a time critical manner. This also included the daily updating of the associated databases. The processing of over 12,000 lots of material representing over 31,000 specimens reflects the volume of identifications required for entomological research and quarantine critical issues at U.S. ports-of-entry.


Review Publications
Beard, J., Ochoa, R., Vega, F.E. 2011. Asca nelsoni sp. nov. (Acari: Mesostigmata: Ascidae), a new mite species from coffee leaf domatia in Costa Rica. Systematic & Applied Acarology Special Publications. 16:7-20.

Dowling, A.P., Bauchan, G.R., Beard, J.J., Ochoa, R. 2010. SEM vouchers and genomic data from an individual specimen: maximizing the utility of delicate and rare specimens. Acarologia. 50(4):479-485.

Menon, P., Ochoa, R., Bauchan, G.R., Joshi, S., Ramamurthy, V.V. 2011. A new genus and species Mangalaus krishianusandhanus (Acari: Eriophyidae) from India. International Journal of Acarology. 37(2):131-142.

Beard, J.J., Ochoa, R. 2011. New flat mite genera (Acari: Trombidiformes: Tenuipalpidae) associated with Australian sedges (Cyperaceae). Systematic & Applied Acarology Special Publications. (2941):1-37.

Ochoa, R., Beard, J.J., Bauchan, G.R., Kane, E.C., Dowling, A.G. 2011. Herbivore exploits chink in armor of host. American Entomologist. 57(1):26-29.

Last Modified: 8/22/2014
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