I am a Museum Specialist in the Department of Botany and the research assistant to curator Jun Wen, whose expertise includes grapes – the plant family Vitaceae, ginseng – the plant family Araliaceae, cherries – the family Rosaceae, and many plant groups found both in eastern Asian and North American that are biogeographically disjunct (species that are related, but separated geographically). Wen is a passionate biogeographer, an inveterate collector of plant specimens, and a strong believer in the collaborative process. Of all the tasks and projects I am given, an opportunity for fieldwork tops the list.
Recently, I was able to participate in a GGI-funded collecting expedition to study the relationships and geographic patterns of sumacs and mosses in North America. For this particular trip we were joined by Dr. Zhumei Ren, a longtime colleague from China. Ren has been on several collecting trips with me in the past, but this was not our usual plant collecting trip. While we often collect plants that are disjunct species between North America and eastern Asia, we are not usually collecting a plant species that has a 48-million-year-old relationship with an aphid. But that is exactly what we set off to do.
The aphid, Melaphis rhois, has co-evolved with two separate plant hosts integral to its life cycle. The primary host are sumac trees (Rhus); the aphid creates a sumac gall upon which it feeds. Galls are abnormal plant growths caused by the feeding or egg-laying activity of insects. The gall created by the Meaphis aphid is the summer home to a single female aphid where she reproduces for several months. The secondary hosts are the mosses growing in the area. As autumn approaches, the galls are slit open and the aphids fly to the moss beds where they reproduce again and overwinter. In the following spring, the larva feather and fly to the primary host for producing and mating. The mated female will produce a single female baby and the life cycle continues. Interestingly the sumac-gall aphids also show a disjunct distribution with the related aphid group, subtribe Melaphidina, distributed in eastern North America and eastern Asia.
Our goal on this trip was to collect samples of the unique sumac species in North America over their geographic range in the eastern U.S. in order to conduct more extensive molecular analysis, particularly focusing on the phylogenetic diversity of the species and its disjunction.
While these sumac trees are common, finding trees with sumac galls is a matter of chance. The galls are located on the undersides of the leaf, are globular, and vary in size with the largest about the size of a golf ball. They are often reddish in color, but can also be yellow to light green. We targeted locations that would encompass their geographic range from south to north, but we had a small window of time in which to collect them: when the aphids are mature, but before the galls are open. We needed to rely on first-person reporting to locate each site.
We hit the lottery with Joe Boggs from the Ohio State Extension Service Office. His directions were precise and he met us on site to relate the history of this particular stand of Rhus/gall activity. Boggs departed for the extension office while we continued to collect plant, gall, and moss specimens. As we were packing up our gear Boggs returned. Because Rhus is a member of the Anacardiaceae family (poison ivies and oaks as well), he was concerned that we were exposed to the rash-causing oil, urushiol. He gave us a bottle of poison ivy scrub to remove the oils—good old Midwestern hospitality—and because of this he became the highlight of our trip.
We continued south to Georgia, made a pit stop at the museum to offload specimens and replenish supplies, and continued north to New York, Vermont, and New Hampshire. It was a frantic road trip to make the collections within the prescribed time limit. We successfully collected in every targeted geographic area. But a road trip like this is not without its favorite moments.
Our favorite saying on this trip came from our vehicle GPS guide, when we veered off the preset course – “Take a U-turn (big pause) if possible” – always sounding like it feared a liability.
The collections made from North America will be studied along with many specimens already gathered in China by Zhumei Ren, Jun Wen, and their collaborators to unravel the biogeographic and evolutionary history of this unique group.
By Zhumei Ren, Museum Specialist, Department of Botany (edited by GGI staff).