Location: Systematic Entomology Laboratory
Project Number: 8042-22000-313-00-D
Project Type: In-House Appropriated
Start Date: Jul 29, 2020
End Date: Jul 28, 2025
The long-term goal of this project is to produce systematic revisions of monophyletic groups of Acari (mites) that are important to U.S. agriculture and transfer this information to stakeholders, regulatory agencies, scientists, and the general public. The project will focus on two mite families: Tetranychoidea (spider mites and flat mites) and Eriophyioidea (gall, rust and bud mites), which are of increasing importance on crops, ornamentals and fruit trees in the U.S. Other related plant feeding superfamilies, like the white mites (Tarsonemoidea), will continue to be monitored. Many genera in the Eriophyioidea are affecting millions of fruit trees (e.g., citrus, apple, avocado, mango and berries), palms and ornamentals, and several species of Eriophyiod mites are strongly linked with the transmission of plant viruses. To complicate manners, many of the viruses may help the mites to affect the plant. The spider mites (several genera, including Tetranychus, Oligonychus, Eotetranychus and Eutetranychus) are major pest of crops and ornamentals and their roles as invasive species have been increasing, which increases the need for new management alternatives. Despite their economic importance and our limited knowledge, these mite genera need rigorous systematic revision, and the tools available for their identification need improvement. This project plan focuses on the following objectives: Objective 1: Conduct systematics and taxonomic research to revise the superfamilies Tetranychoidea and Eriophyoidea (Acari), and curate and expand the U.S. National Mite Collection in support of this effort. [NP304, C1, PS1A; C2, PS2B; C3, PS3A and 3B; C4, PS4A and 4B]. Objective 2: Expand and enhance web-based information resources for systematic acarology, emphasizing mite-plant-associations and their taxonomy, ecology, biology and geographic distributions. [NP304, C1, PS1A; C2, PS2B; C3, PS3A and 3B; C4 PS4A and 4B].
Morphological characters will be identified through the examination of specimens using dissecting, DIC, Phase Contrast, CLSM, TT-SEM and Cryo SEM. Use of Cryo-SEM in mite taxonomy is revealing remarkable new character systems that were previously unknown and allowing researchers to re-evaluate poorly understood morphological characters that are difficult, if not impossible, to evaluate based on traditional slide-mounted preparations. This technique not only greatly expands the array of morphological characters available, offering them in greater detail, but it also provides valuable behavioral characters, especially with respect to understanding mite feeding behavior. Cryo-SEM will be used to confirm the intricate details of certain morphological characters visible with light microscopy, especially those of the tarsi and empodia. The novel characters available with Cryo-SEM (e.g., tegument texture and tarsal morphology) will be investigated and assessed using a minimum of 5 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. TT-SEM and CLSM technologies will be used to further the morphological studies. Although the research will focus primarily on morphological and ecological characters of 4 tetranychid genera and 4 eriophyid genera, these data sets will be augmented with molecular data (COI, 18S, 28S, EF-1') as an exploratory avenue for systematic research in these taxa. We will collaborate with Dr. Ashley Dowling and his team at the University of Arkansas who have expertise in molecular characterization of mites. Character information will include the external and internal morphology of mounted flat mites, adults and immatures, combined with the molecular data and analyzed using TNT and MrBayes. Live specimens used for Cryo-SEM studies will be solicited from colleagues and/or brought into the laboratory from domestic and/or foreign fieldwork following standard quarantine regulations and evaluated for morphological characters. In addition, some slide-mounted specimens will be borrowed from or examined at various institutions worldwide, especially the type specimens located in Canada, Brazil and Australia. More than half of the type specimens located at the National Mite Collection (Beltsville, MD) have been studied under DIC and Phase Contrast microscopy. Additional specimens will be collected from regions that are poorly represented in accessible collections, including Australia, South America, India and China. Methods of preparation and preservation will follow those previously described for slide mounting and Cryo-SEM.