Why do we have amber forests? The relationship between resin production and amber deposits
Ecology and Biodiversity of Plants and Ecosystems
Final Report Abstract
This project was to understand the reasons that cause plants to produce resin and how this might link to large amber (fossilised resin) deposits in the rock record. Resins are thought to be part of a plant’s set of defences, and many reasons have been previously suggested for resins to be produced and then exuded out of a plant. To be able to answer this the approach was through a mixture of observations of the natural world and through experiments. Then the project evaluated whether there are distinctive chemical signatures in the modern resins that point to a particular reason for the outpouring, and whether this can then be traced in an amber so we can identify a reason for a resin outpouring in the past. The main chemical analysis was using Fourier-Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy plus carbon isotopes. The Araucariaceae plants were used as models for this project as they are highly resinous today, and are the source plants for many ambers in the fossil record. Today the Araucariaceae are found mostly in the Southern Hemisphere, with a centre of biodiversity in New Caledonia. There is also a species in New Zealand which is linked to huge sub-fossil resins and ambers there, providing a perfect link for this project. The ‘real world’ field observations complement the experimental work. The lucky discovery of an arboretum in New Caledonia growing a wide range of endemic and non-native Araucariaceae meant many species’ resins (and other exudates) could be sampled at the same location, allowing the chance to understand any differences between such closely related species and made an excellent addition to the field-collected samples. Different reasons for resin production (e.g., insect damage, fire, physical trauma, and drought) were observed in the natural populations and in the experiments. The experiments has trees subjected to different treatments to observe whether and how much resins are produced., under controlled conditions which is important when trying to disentangle chemical signals. Through the chemical analyses, it was discovered that the resins show so much natural variation in their chemistries, not just between different species, but also between individuals of one species. This variation was even greater in the wild-sourced samples as the ecological differences also affected the resin chemistries, which were not present in the arboretum or experimental set up. However, there was even resin chemistry variation discovered within in one individual plant, depending where the resin originated on the plant. Some natural variation was expected in a biological product, but this level of variation has never been documented before. This means that in future we must amend our testing from the often sole sample, to include far more samples to be able to give us a fair better idea of the actual variation present in resins and ambers. Furthermore we need to now investigate how many resins actually have overlapping chemistries, as this project highlighted this variation means that some resins from different species cannot be chemically distinguished. A surprise was the discovery that in the Araucariaceae family, some of the species produce different exudates, not just resins. Although this had been noted for a couple of species previously, I could show that several members of this family produce resins, gums and gum-resins, some species even produce all three types. The careful collection of wild-sourced samples and the chemical analyses here allowed these different exudate types to be thoroughly identified. Another unexpected discovery was the identification of the first fossilised gum in the rock record – this was unexpected as gums are water soluble and so were not thought to survive fossilisation.
Publications
- 2017. Carbon-isotope variability prevents faithful palaeoatmosphere reconstructions with fossil conifer resin (amber): the Cretaceous case study. Geochimica et Cosmochimica Acta. 199: 351–369
Dal Corso, J., Schmidt, A. R., Seyfullah, L. J., Preto, N., Ragazzi, E., Jenkyns, H. C., Delclòs, X. & Roghi, G.
(See online at https://doi.org/10.1016/j.gca.2016.11.025) - 2018. Marine microorganisms as amber inclusions: insights from coastal forests of New Caledonia. Fossil Record. 21: 213–221
Schmidt, A. R, Grabow, D., Beimforde, C., Perrichot, V., Rikkinen, J., Saint Martin, S., Thiel, V. & Seyfullah, L. J.
(See online at https://doi.org/10.5194/fr-21-213-2018) - 2018. Production and preservation of resins – past and present. Biological reviews. 93: 1684–1714
Seyfullah, L. J., Beimforde, C., Dal Corso, J., Perrichot, V., Rikkinen, J. & Schmidt, A. R.
(See online at https://doi.org/10.1111/brv.12414) - 2018. The Carnian Pluvial Episode and the first global appearance of amber. Journal of the Geological Society of London. 175: 986–988
Seyfullah, L. J., Roghi, G., Dal Corso, J. & Schmidt, A. R.
(See online at https://doi.org/10.1144/jgs2017-143) - 2020. Cretaceous gnetalean yields first preserved plant gum. Scientific reports. 10: 3401
Roberts, E. A., Seyfullah, L. J., Loveridge, R. F., Garside, P. & Martill, D. M.
(See online at https://doi.org/10.1038/s41598-020-60211-2) - 2020. Revealing the diversity of amber source plants from the Early Cretaceous Crato Formation, Brazil. BMC Evolutionary Biology. 20:107
Seyfullah, L. J., Roberts, E. A., Schmidt, A. R., Ragazzi, E., Anderson, K. B., Rodrigues do Nascimento, D., da Silva Filho, W. & Kunzmann, L.
(See online at https://doi.org/10.1186/s12862-020-01651-2) - 2020. The Carnian Pluvial Episode: mass extinction and dawn of the modern world. Science Advances 6:eaba0099
Dal Corso, J., Bernardi, M., Sun, Y., Song, H., Seyfullah, L. J., Preto, N., Gianolla, P, Ruffell, A., Kustatscher, E., Roghi, G., Merico, A., Hohn, S., Schmidt, A. R., Marzoli, A., Newton, R. J., Wignall, P. B. & Benton, M. J.
(See online at https://doi.org/10.1126/sciadv.aba0099) - Experimental induction of resins as a tool to understand variability in ambers. Fossil Record, 24, 321–337, 2021
Seyfullah, L. J., Roberts, E. A., Jardine, P. & Schmidt, A. R.
(See online at https://doi.org/10.5194/fr-24-321-2021)
