Periodic Reporting for period 4 - ANICOLEVO (Animal coloration through deep time: evolutionary novelty, homology and taphonomy)
Reporting period: 2020-07-01 to 2021-04-30
The project’s societal importance lies in its position at the interface of several scientific disciplines and rooting in palaeontology. As such, the project naturally lends itself to inspiring the public in the wonders of the natural world and encouraging prospective future scientists via the provision of high-profile role models and cutting-edge research discoveries.
The overall objectives of the research relate to the evolution of coloration in fossil vertebrates and insects. Regarding vertebrates, the key objectives centre around resolution of the biological distribution, geometry, chemistry, function and evolution of melanin. Regarding insects, the key objectives relate to the origins, chemistry and evolution of colour patterns and 3D photonic crystals. All objectives are underpinned by taphonomic insights in order to maximise the credibility of the data.
Several important conclusions have already been published. Broad phylogenetic analysis of the biology of melanin across vertebrates reveals tissue-specific and taxonomic trends in melanin abundance, location and chemistry that supports evidence for evolutionary tradeoffs between function and cytotoxicity. Melanosome chemistry, however, is not preserved in fossils intact, and instead the metal chemistry of melanosomes from different tissues can converge during thermal maturation, potentially masking real original differences in chemistry and related anatomical and taxonomic interpretations. Fossil skin can preserve evidence of the full colour gamut via diverse chromatophores in authigenically mineralized tissue and can preserve evidence of a deep co-evolutionary history with feathers. Preservation of branched feathers in pterosaurs confirms feathers originated in the avemetatarsalian ancestor of pterosaurs and dinosaurs in the Early Triassic. Finally, 3D photonic crystals preserved in weevils from the Swiss Pleistocene likely functioned in substrate matching.
The results have been disseminated primarily in 24 publications (with an additional 30 papers in preparation or in review), including high-profile publications in Nature Communications (n=2), Nature Ecology & Evolution (n=2), Trends in Ecology and Evolution (n=2), Science Advances (n=1), Current Biology (n=1), Proceedings B (n=1), PNAS (n=1) and Journal of the Royal Society Interface (n=2). The results have also been disseminated to the scientific community via 63 conference presentations (50 of these oral presentations) across 44 international meetings, plus 16 invited keynotes and lectures (by the PI). The project results have been disseminated to the public via 67 public engagement activities, including exhibits, lectures, a website and blog, news articles, TV and radio interviews and documentaries.
The main results of the project include several important discoveries that have already been published. These include internal melanosomes in fossil and extant vertebrates, a new tool for interpreting fossil soft part anatomy, preservation of diverse colour-producing cells and keratinocytes in fossils, preservation of branched feathers in pterosaurs, the controls on the chemistry of fossil melanosomes, single diamond 3D photonic crystals in fossil weevils, and new models for the functional evolution of melanin in vertebrates.
This project also represents a major advance in research approach. We tackled various issues relating to colour evolution in animals using a very grounded, systematic, and comprehensive analytical approach. Many of the techniques we employed are rarely used in palaeobiology, e.g. tissue histology, microspectrophotometry, fourier transform infrared radiation spectroscopy, Raman spectroscopy, and synchrotron-X-ray absorption spectroscopy, but this project has played an important role in embedding these approaches in the palaeobiology mainstream. In particular, we have now published a substantial body of work using synchrotron-XAS approaches on both fossil and extant animals; this, combined with our critical taphonomy-based narrative, has enhanced the credibility of XAS data from fossils.
This project highlights the need for future palaeobiological studies on fossil soft tissues to use a broad phylogenetic approach. In doing so, our work has enabled robust interrogation of evolutionary trends relating to keratinous tissues, melanin biology and chemistry for the first time. Critically, this approach even allows integration of fossil and genomic data, highlighting the potential for new future research avenues.
This project is also unique in its strong foundation in taphonomy – both experimental and theoretical. This is essential to accurate interpretation of fossils and application of fossil data to diverse evolutionary questions. Our publications have established a new standard for reporting experimental taphonomic data by including a dedicated section justifying our experimental approach, to facilitate progress beyond the “black box” model and to cement the credibility of experimental taphonomy in the scientific community.