In this last of a series of posts (1,2,3) on the future of botany, I want to take up a topic that seems to be receiving more attention lately: the relationships between specimens and photographs. Even as stout a defender of herbarium specimens as myself has to admit that there is a considerable difference between them and living plants, between brown and virtually two-dimensional as opposed to colorful and in 3-D. Photographs have the storage advantages of specimens while providing at least some of the information that specimens lack. In addition, digital photography has made it cheaper to take photographs and easier to store them.
Yet despite their usefulness, plant photographs, at least for some species, are not easy to come by. In a 2021 article in Nature Plants, Pitman et al. reported on a survey of 25 online databases of field photographs and found that they held only about 53% of the 125,000 vascular plant species from the Americas. The databases they searched included those hosted by botanic gardens, natural history museums, and other entities such as Flora of the World and Plantsystematics.org. Also, three social media and community science platforms were surveyed: iNaturalist, Pl@ntNet and Flickr. These three accounted for 37.8% of the species, and photos of about a third of these species were not found on any other sites. Flickr and iNaturalist also had the best geographic coverage.
Not surprisingly, North American species were more likely to be photographed than those of central and South America. But there were wide variations in coverage, with 71.9 % of Bolivian species pictured versus 56.8% of those in Brazil. There were also differences among plant families with 98.1% of the Liliaceae captured, but only 18.7% of the Piperaceae, which have less showy flowers. Not surprisingly, rare plants were less likely to be photographed as were relatively new species. In addition, the researchers found that when they rechecked their results after several months that a number of species were represented that hadn’t been there earlier. So this is definitely a changing landscape, but one that’s troubling to those attempting to document and study biodiversity.
The Americas are not the only areas that have this problem. A new Australian study of (Mesaglio et al., 2023) revealed that 17.6% of the Australian flora of 21,077 vascular plant species are not represented by any photographs. Here 33 online resources were used, again including social media and community science platforms. Obviously the coverage is much better than for the Americas. Australia has a well-organized system of state herbaria, was an early adopter of digitization, and is able to draw upon an up-to-date list of its species. Still there are gaps, again related to the rarity of species or their recent discovery, and there are also geographic disparities. While Western Australia is the most species-diverse state there are some areas that are very difficult to access, hence less photography has been done. Other reasons for gaps cited by the authors were for plants that are difficult to identify or that lack “charisma.”
Both articles stress the importance not only of the number of photographs but their quality. These need to be high-resolution and capture as many of the plant’s identifying characteristics as possible. Thus the best photographs are likely to be those taken by individuals who know enough about plant systematics to literally focus on identifying traits. This is a topic that Carlos Gómez-Bellver (2019) and his colleagues in Barcelona address in an article where they propose standards for photographs to complement herbarium vouchers. However, the guidelines would also be useful for photographs not physically attached to specimens, but linked to them as part of the extended specimen concept.
The authors list six cases where photos would considerably increase a specimen’s taxonomic value. First are large species such as a palm, where photos of the plant as a whole and its habitat would help to put the specimen into context. Succulent or spiny plants, that are difficult to prepare would also benefit from such photos, with only small pieces of the plant itself attached; the same is true of plants with toxic substances. Then there are species for which little remains but seeds and withered material, also species that lose important morphological traits when they are pressed and dried. There might be cases where the specimen is the only one in the vicinity, so the photo would serve as a voucher; the same would be true of plants at sacred sites where collection might be considered disrespectful.
The authors call for the development of a protocol with standards that photographs must meet to be considered as reference material to be tied to a voucher. I can’t go into all the elements here, but they include reflecting the entire size of the plant and its habitat. The photo must also include the standard metadata about date and location, the collector, and precise geolocation. What they term “fusion vouchers” are those that include both a specimen and photos; these would be stored in herbaria. Photo vouchers alone could be filed in a variety of ways which are discussed. At this time, there is no standardization. But as the other articles I’ve discussed here make clear, it would be important for the photos to be accessible digitally.
Gómez‐Bellver, C., Ibáñez, N., López‐Pujol, J., Nualart, N., & Susanna, A. (2019). How photographs can be a complement of herbarium vouchers: A proposal of standardization. TAXON, 68(6), 1321–1326. https://doi.org/10.1002/tax.12162
Mesaglio, T., Sauquet, H., Coleman, D., Wenk, E., & Cornwell, W. K. (2023). Photographs as an essential biodiversity resource: Drivers of gaps in the vascular plant photographic record. New Phytologist, 238(4), 1685–1694. https://doi.org/10.1111/nph.18813
Pitman, N. C. A., Suwa, T., Ulloa Ulloa, C., Miller, J., Solomon, J., Philipp, J., Vriesendorp, C. F., Derby Lewis, A., Perk, S., Bonnet, P., Joly, A., Tobler, M. W., Best, J. H., Janovec, J. P., Nixon, K. C., Thiers, B. M., Tulig, M., Gilbert, E. E., Campostrini Forzza, R., … Hilo de Souza, E. (2021). Identifying gaps in the photographic record of the vascular plant flora of the Americas. Nature Plants, 7(8), 1010–1014. https://doi.org/10.1038/s41477-021-00974-2