This week we highlight an article hot off the press in the new year, a review penned by Dr. Mason Heberling at the Carnegie Natural History Museum. In this paper, Heberling describes how herbarium specimens have, can, and should be used to study plant functional traits.
Functional traits, as defined in the article, are "any morpho-physio-chemical-phenological characteristics that serve as proxies for understanding individual fitness" (Heberling 2022). In other words: anything that is measured from or on a plant that is used to approximate how successful that plant is. Ecologists have turned their attentions toward functional traits relatively recently; Heberling cites landmark works from as early as 1997. Still, an offhand search of Web of Science with the keyword "functional trait" or "functional traits" results in over 11,000 papers (our research, not Heberling's), clearly revealing high interest in trait-related research. However, Heberling noted that few studies in this particular arena use herbarium specimens, despite the stupendous spatiotemporal and taxonomic coverage that specimens can provide. He calculated that, if you measured only a single trait on all 396 million specimens that are estimated to exist, you could grow the most commonly used trait database, TRY, by 3400%. This could be a functional trait windfall.
Heberling explains that there is a cornucopia of questions that could be investigated using specimen-derived functional traits. Researchers can measure plant and leaf size and shape; density and patterns of leaf veins and stomata (small pore-like openings in the surface of the leaf that allow the exchange of gases); tissue chemistry; pollen shape, size, and composition; presence of symbiotic organisms; plant phenological traits (e.g., flowering or fruiting status); and many other traits yet unexplored. These all can be related to the time, place, and conditions in which the plant was collected to inform our understanding of these plants' ecological roles and evolutionary strategies. The few studies that have dived into this data source have already discovered critical patterns, such as significant morphological shifts in introduced species over only 150 years (Buswell et al. 2011), and a decrease in leaf nitrogen (an important component in the structures that conduct photosynthesis) in the last 100 years (McLauchlan et al. 2010). Such research can pave the way for further studies of the ecological, evolutionary, and economic impact of these changes.
All this being said, Heberling posits that realizing the potential of herbariums specimens for functional trait research relies not only upon ecologists recognizing these specimens as a viable source of data, but also on (1) the continued development of ways to account for well-documented biases in specimen-based datasets, and (2) improved collection practices that capture trait variation and other key data. With attention paid to these two aspects, Heberling writes, and "Bolstered by more than a decade of digitization and emerging initiatives, the role of herbaria in modern research should only strengthen" (110).
Works Cited
Heberling JM. 2022. Herbaria as big data sources of plant traits. International Journal of Plant Sciences. 183(2):87-118.
Buswell JM, Moles AT, & S Hartley 2011 Is rapid evolution common in introduced plant species? Journal of Ecology. 99:214–224.
McLauchlan KK, Ferguson CJ, Wilson IE, Ocheltree TW, & JM Craine. 2010 Thirteen decades of foliar isotopes indicate declining nitrogen availability in central North American grasslands. New Phytologist. 187:1135–1145.
Buswell JM, Moles AT, & S Hartley 2011 Is rapid evolution common in introduced plant species? Journal of Ecology. 99:214–224.
McLauchlan KK, Ferguson CJ, Wilson IE, Ocheltree TW, & JM Craine. 2010 Thirteen decades of foliar isotopes indicate declining nitrogen availability in central North American grasslands. New Phytologist. 187:1135–1145.
