Scale insects are plant pests of considerable significance in agriculture and forestry, causing billions of dollars in damage annually. For this reason, the taxonomy and identification of species is quite sophisticated and specialized, but relationships among the larger lineages are still poorly explored. With this grant, research will be expanded on the evolutionary relationships among the basal families of scale insects, using anatomical structures of the adult females and males as well as DNA sequences. The results will allow informed predictions to be made about groups whose biology (e.g., plant hosts) is poorly known. Since scale insects are so diverse in ambers 130 to 20 million years old, they are a model group to examine how plant-feeding insects have evolved with respect to the flowering plants (angiosperms). Scales preserved in ambers from around the world will be studied, and the anatomical data from the fossils in a large data set with the modern species analyzed. Select amber specimens will be scanned at the Advanced Photon Source, Argonne National Laboratory, to visualize obscured microscopic structures. The project will allow to determine when the families of scale insects diverged in geological time, and assess if their evolution coincided with that of the flowering plants.
The PI and co-PI are actively involved with informal science education, and the funded work will be incorporated into it. The Co-PI has designed Entomology sessions of the biodiversity course for the NSF-sponsored Science Research Mentoring Program with which the AMNH Education Department is preparing the production of web material, and will be available through this online portal. The PI mentors two high school students in this program, working on amber. The Co-PI will also be involved in informal public education, including hands-on laboratory experiences for middle and high school students in the Sackler Educational Laboratory. Lastly, a product of this research will be an online interactive identification key available on the co-PI?s research website.
Plant-insect relationships are one of the most remarkable symbiotic terrestrial associations. Although many studies have dealt with the relationships between plants and their pollinators, understanding the evolutionary diversification of plant-feeding insects relative to their hosts is still in its infancy. Scale insects (Hemiptera: Coccoidea) are plant-feeding parasites closely related to aphids. Despite their impact on human societies as destructive pests in agriculture and horticulture, use in the production of dyes, lacquer, or biological control of invasive plants, the evolution of scale insects remains unclear and questions such as how they evolved with their host plants cannot be answered yet. One of the major challenges in this group is to link fossil information with Recent species. In fact, males and females are extremely different and today’s scale insects are known through the females, whereas only males are studied in the fossil record. Additionally, there is a lack of resolution in the family-level relationships. This is especially true for the archeococcoid group that includes all the less common families of scale insects but also the most ancient ones. In contrast, the most common and diverse groups belong to the neococcoids and feed in majority on flowering plants. We therefore wanted to test whether the neococcoid origin and diversity was a result of co-evolution with the rapid diversification of flowering plants in the middle of the Cretaceous (around 100 millions years ago). Our project addressed the evolutionary history of scale insects by first producing a new revision of fossil scale insects from ambers deposits ranging from 135 to 45 million years old. Most fossil inclusions came from ambers excavated by the American Museum of Natural History (Myanmar and India), although the oldest inclusions came from Lebanese amber (National Museum of Natural History in Paris). Using microphotography and traditional drawing techniques, this revision allowed to uncover new diversity of scale insects, today extinct. Secondly, using extensive morphological work from worldwide scale insect collections (from both females and males) and three molecular markers from Recent species, we estimated ages of the main lineages of scale insects by incorporating morphological information of extinct groups and using these fossils as calibration points. Our study, including almost all known scale insects families and incorporated more than 40 fossil species, found that the neococcoid group originated about 100 million years before the radiation of flowering plants, and that, by the middle of the Cretaceous, most Recent families were already established.
