“Rise of Modern Biological Diversity in the Phanerozoic” Roundtable Discussions

Roundtable discussions at the 2015 Critical Transitions in the History of Life Workshop addressed key topics and challenges facing researchers today. Participants discussed opportunities for data sharing, technological advancements in analytical tools and mutually-beneficial ways to collaborate on further studies. Four separate roundtables were held on-site, with one additional discussion taking place at the Advance Photon Source of the Argonne National Lab. Links to the highlights, summaries and participant lists for each discussion are below.

Timing and Origins of Modern Biodiversity and Ecosystems

This discussion focused on two major issues. First, participants cited the need for better understanding of geochronology of major fossil biotas, which is an enduring problem for researchers. Although there has been significant progress in dating the age of major fossil biotas, there is still a pressing need to improve their geochronologic and stratigraphic resolutions. For several major biotas of China, there is an obvious need for consensus on definition of each biota, and how to better circumscribe its geographic scope, and to summarize the taxonomic diversities of the faunas and the flora. For an understanding of the evolutionary assembly of communities, there is a need for consistent approaches to time-averaging in taphonomic and paleoecological studies. Improved biostratigraphic and geochronologic data will allow more accurate timing estimates of biotic turnover and evolutionary rates. Although hardly new, this is the foundational framework for examining biotic response to changes in climate and geosphere.

The second main topic was how to improve disparity and diversity metrics, and on using ecomorphological approaches to gauge patterns of faunal changes. Fossil studies need new methods, such as comparing the disparity patterns of fossil assemblages with disparities of extant ecological communities, to detect shifts in community structure. One new method used food web-based network analysis of paleoecological changes to establish the biotic and environmental interactions during critical transitions.

These topics prompted two practical suggestions. First, data-sharing needs to improve for information on stratigraphic sections and voucher fossil specimens. Second, a number of fossil-bearing units and sites should be used as reference case studies. These “focus sites” or “model assemblages” with fine-scale chronology and biotic diversity and disparity can serve as a baseline to improve our overall understanding of the biotic interaction during critical transitions.

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The Rise of Modern Diversity: Combining Paleontological and Molecular Perspectives

Integrating molecular and paleontological perspectives requires a central database or archive of genomic data, phenomic data, and stratigraphic data for fossil calibration. Participants suggested a common platform for researchers to foster best practices in combining molecular systematics with fossil data. This common platform requires the construction of a comprehensive database of key fossils employed in calibrating molecular phylogenies, the content of which should be peer-reviewed and continuously updated. Such initiatives already exist (e.g http://fossilcalibrations.org), but need to be supported and expanded.

Participants agreed that website mirroring would be useful in protecting and disseminating the information, and that scientists could encourage Chinese and American websites to lead the way. These databases will also require significant IT infrastructure, data storage capabilities, administration and the physical capability to carry out significant analytical computations.

Major topics in evolutionary development should be used to frame case studies of evolutionary transition in the fossil record. Though hardly novel in theory, recent advances in technology (various scanning methods for fossils and embryos) and novel lab analytical tools (e.g. new understanding of genetics and morphogenesis underlying phenotypic features also seen in fossils) have revitalized this approach for paleontological research.

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Sedimentology, Taphonomy and the Study of Fossilized Soft Tissues in Major Lagerstätten

Presentations on this theme focused on the exceptional preservation in fossil Lagerstätten worldwide, with an emphasis on China. Participants discussed the need for a comprehensive understanding of the taphonomy and geochemistry of 'exceptional preservation.’

The term 'exceptional preservation' broadly covers conditions where soft tissues of extinct organisms are preserved, but a great diversity of preservational modes exist. Our understanding of the biogeochemistry of how soft tissues can be preserved in different preservational modes has lagged behind the discovery of new sites with exceptional preservation.

During the discussion, participants identified two major priorities. First, research needs to focus on developing novel tools and methods for studying disparate modes of preservation. Second, researchers need to use technological resources to standardize methods and protocols in characterizing the fossil soft-tissues, or at least work toward such standardization. Advances will permit more precise formulation of hypotheses of preservation, to replace more vague hypotheses that have been formulated in the past.

Participants also raised the idea of creating a shared map of the stratigraphic and geographic distribution of exceptional preservations in the fossil record. A majority of case studies on exceptional preservations dealt with individual fossil assemblages, and these scattered case studies need to be placed in the context of the total fossil record. An accessible web portal for such information could be one solution.

Out of the discussion also came an appeal for the larger scientific community not to underestimate the potential for unexpected preservation of soft tissues in the fossil record. Participants cited recent examples of previously unexpected preservation that include ancient DNA records now going back to the Pleistocene. Also, preserved proteins that can inform on the phylogeny of extinct mammal taxa, and possibly even Cretaceous dinosaurs, were mentioned in this regard. Other examples include the preservation of melanosomes in numerous Jurassic and Cretaceous specimens from Chinese Lagerstätten and elsewhere.

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Climatic and Biotic Evolution in the Neogene

Participants in this session focused to a large extent on Neogene faunal and climate evolution as consequence of tectonic uplift of the Tibetan Plateau, with a strong focus on mammalian turnover and paleobiogeographic distribution.

The discussion highlighted the need to analyze the evolutionary patterns at relevant time scales of Neogene. For Neogene biotic and climatic evolution, especially the assembly of fossil mammal communities, participants saw value in study of the interaction of principal clades as a ways to decipher paleoecological communities of mammals.

It is very desirable to establish a common denominator for current databases that have different levels of proprietary data (including unpublished data), among MIOMAP based in North America, NOW based in Europe and Asia, and the widely used Paleobiology Database (PBDB).

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Discussion at Advance Photon Source of Argonne National Lab

At the Argonne National Laboratory (ANL) Advance Photon Source (APS) facility, several workshop participants presented case studies of fossils using synchrotron tomography.

APS scientists and workshop participants discussed ways of fostering new research using APS beamlines. APS staff extended an open invitation for participants to develop synchrotron-based projects, in which both US and Chinese scientists expressed strong interest.

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