It is therefore possible to assess the chemical composition of an organism’s anatomy and use this same anatomical region as a point of comparison among other related species. Matter reflects, absorbs, and emits radiation in varying proportions at different wavelengths, creating what is known as a spectral signature, measured light encoded with information. As such, hyperspectral analysis differs from conventional analysis of photographs or other digital media (e.g. By analyzing how light (electromagnetic radiation) interacts with matter (even an organism), it is possible to determine an object’s chemical composition and physical structure. Hyperspectral analysis is a well-established methodology in the Earth sciences with roots in chemistry and physics. What if another method for rapid identification of polymorphism in natural populations existed? Moreover, what if assessment of phenotypic polymorphism could be undertaken in the field while living organisms are held in person, rather than in a lab far away? We propose that hyperspectral assessment of live organisms, and the generation of spectral signatures for individual taxa (or operational taxonomic units, OTUs) can provide: (1) rapid assessment of phenotypic variability in the field, (2) discriminate organisms along meaningful categories like taxonomy or ontogeny, and (3) complement or even reconcile morphological taxonomy with molecular barcoding methods. However, both traditional morphological taxonomy and molecular barcoding still require considerable benchwork: i.e., an intensively trained taxonomist who completes microscopy and meristics to identify phenotypic structures or a technician that performs PCR reactions and sequencing for barcoding. Rapid identification of phenotypic diversity in the field gives biodiversity researchers the ability to streamline their collections and surveys, as well as brings assessment of phenotypic variation back to the forefront of systematics. Complementing surveys and natural history collections, there are methods like DNA barcoding and meta-barcoding which have been developed to catalog biodiversity, for both previously known and unknown organisms 7. The need to find, categorize, and curate biodiversity is both critical for the prioritized deployment of conservation resources and for maintaining a record of biodiversity before such organisms are lost. The biological sciences face two dire and disturbing issues: (1) increases in extinctions of animals across all continents and oceans 1, 2, 3, 4, as well as (2) a shrinking pool of taxonomists trained to identify these organisms 5, 6, 7. While spectra do not serve as an alternative to the collection of curated specimens, hyperspectral data of fishes in the field should help clarify which specimens might be unique or undescribed, complementing existing molecular and morphological techniques. Herbivorous pacu spectra were more like one another than they were to piranhas however, our method also documented interspecific variation in pacus that corresponds to cryptic lineages. We analyzed 47 serrasalmid species and could distinguish spectra among different species and clades, with the method sensitive enough to document changes in fish coloration over ontogeny. We demonstrate that spectral signatures of individual, live fish specimens can accurately capture species and clade-level differences in fish coloration, specifically among piranhas and pacus (Family Serrasalmidae), fishes with a long history of taxonomic confusion. Although hyperspectral data have been mostly used to study landscape ecology, floral diversity and many other applications in the natural sciences, we propose that spectral signatures can be used for rapid assessment of faunal biodiversity, akin to DNA barcoding and metabarcoding. Hyperspectral data encode information from electromagnetic radiation (i.e., color) of any object in the form of a spectral signature these data can then be used to distinguish among materials or even map whole landscapes.
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