In the last post, I introduced Vicki Funk, a plant systematist who is a research scientist and curator at the U.S. National Herbarium, part of the Smithsonian Institution’s National Museum of Natural History. There I mentioned that Funk had recently published a review article called “Collections-Based Science in the 21 Century,” published in the May 2018 issue of the Journal of Systematics and Evolution. As with most review articles, it begins with a historical perspective. The first sentence is a bold claim: “Major revolutions in scientific thought have occurred because of collections-based research” (p. 175). Funk is in a position to know both because she works in an institution with a premier natural history collection, and because she herself has contributed to today’s revolution in how collections are accessed and utilized.
Funk begins with the age of classification and Carl Linnaeus’s heavy reliance on natural history collections in creating his artificial system of classification and nomenclatural reform. Michel Adanson and Antoine Laurent de Jussieu, working at the botanical garden in Paris with its notable herbarium, devised natural classification schemes that in various forms eventually replaced the Linnaean artificial system. The 19th century, Funk notes, began with Alexander von Humboldt’s expedition to Latin America that gave him the perspective to develop the field of biological and physical geography, along with ecology and meteorology. He and his traveling partner Aimée Bonpland collected 50,000 specimens, documenting many new genera and species as well as the relationship between geography and species distributions. Later, Charles Darwin, Joseph Dalton Hooker, and Alfred Russel Wallace not only collected specimens but used them to build on Humboldt’s work and to document the concept of species change. With examples like this Funk makes clear the connection between collection and theory building, as well as the importance of great natural history museum collections, many of which were built in the 19th century.
Funk terms the 20th century the “Age of Synthesis” in reference to the evolutionary synthesis that developed at mid-century and to “four collection-based ideas and methods that changed . . . the way we do science” (p. 178). The first was the concept of continental drift and with it the idea that land bridges between continents had existed in the past. Both Humboldt and J.D. Hooker argued for these from the similarities among organisms in areas that are now separated by great distances. Second was the development of phylogenetic systematics or cladistics, a field to which Funk has contributed a good deal both theoretically (1991) and in terms of her research, especially on the Asteraceae. Cladistics deals with using derived characters to objectively construct relationships, then grouping taxa so all are descended from a single common ancestor without omitting any of its descendants. This is a complex field, and as a recent issue of the American Journal of Botany (August 2018) on fossil plants reveals, there are problems that arise when only living species are used in creating monophyletic groups, so fossil collections are crucial to the process.
Under the third 20th-century trend, Funk lists databasing collections, biodiversity science, and niche modeling. This is a huge triumvirate, but with its parts closely tied together. Databasing collection data—specimen identification as well as place and time of collection—makes it possible to more easily assess data on the biodiversity of a region as well as on how it may be changing over time. It also allows rigorous niche modeling, a term for techniques employing occurrence data to model the possible spatial extent of a species based on geographical and climatic data. Ecology has always been a field using sophisticated mathematical models but the availability of digital data and high-speed computing have caused an explosion in research. And this is really only the beginning, as more collection data and analytic tools come online.
The final concept Funk cites as developing in the 20th century is molecular phylogenetics, the analysis of gene sequences as a way to discover phylogenetic relationships. She writes: “Collections are an excellent source of material for the extraction of DNA, but they are also important because they provide the vouchers of the DNA sequences, and their presence allows us to check the identification of samples and to gather the data needed to ask questions about character evolution and modes of speciation” (p. 180). These vouchers usually contain at least some geographic information, bringing in the biogeography she mentioned earlier. Molecular systematics helped to clear up some arguments about derived characters used in cladistics and resulted in a major reorganization of plant phylogenetics. As will become apparent in the next two posts, sequencing techniques have changed rapidly during the latter part of the 20th and into the 21st century, increasing the efficacy of DNA analysis with herbarium specimens. These tools now allow sequencing of species for which no fresh material is available because the species are rare, inaccessible, or even extinct. If historical material is available, they also enable work on how the genetics of a species may have changed over the last few hundred years.