2015 Annual Science Report
Massachusetts Institute of Technology Reporting | JAN 2015 – DEC 2015
Early Animals: The Origins of Biological Complexity
We seek to understand the interactions of ecological, environmental and developmental processes that generate biological novelty and innovation, with particular emphasis on the events associated with the origin and early evolution of animals. The larger goal is to develop a general model of novelty (the origin of new organismal characters) and innovation (the ecological and evolutionary success of these novelties) and determine whether it applies through the history of life. Alternatively episodes of novelty and innovation may be dominated by historical contingency so that no general model can be developed.
Doug Erwin has continued to focus on articulating a general framework of novelty and innovation, a long-term project on which significant progress was made this year. Novelty and Innovation are frequently conflated but are logically distinct. Considerable progress has been made on one of the major outputs of this project, and several papers have been published this year dealing with various aspects of novelty and innovation. A précis of the framework was published this year in Current Biology and a longer treatment will be completed this year.
NAI-funded graduate student Sarah Tweedt is nearing completion of her work. Sarah Tweedt studies the origins of development and major developmental change in the earliest history of multicellular organisms and animals. Her work covers the oldest macroscopic Ediacara biota as well as exceptionally preserved Cambrian fossils. Molecular divergence estimates place the origin of animals in the Cryogenian – long before their first appearance in the fossil record. To better understand the developmental capacities of these early lineages, Sarah and Douglas Erwin undertook a survey of the published comparative and experimental developmental biology literature, focusing on pre-bilaterian clades. They reconstructed minimum developmental capabilities for sponge, cnidarian, and bilaterian last common ancestors; this work was published in spring 2015 in a special volume on the evolution of multicellular life.
The early Cambrian lobopods are widely thought to have given rise to all true arthropods, but this would imply a substantial evolutionary transition in animal development occurring in the Precambrian. Thus far there is little fossil evidence for this scenario, and early panarthropod relationships remain poorly resolved. For her thesis research Sarah is working to build a robust lobopod-arthropod phylogeny to test the limits of our knowledge of rapid morphological change, and ultimately to help understand major developmental change in the ancient panarthropod lineage. Sarah traveled to the Nanjing Institute of Geology and Paleontology in the summer of 2015 (not using NASA or NAI funds) to examine the lower Cambrian Chenjiang lobopod fossils, which comprise the majority of Cambrian lobopod diversity. She presented some of this work at the annual Geological Society of America meeting in the fall of 2015.
Additionally, Sarah continues to work on the summary and description of 80+ specimens of a new macroscopic Ediacaran organism from Namibia. She plans to join Douglas Erwin and Emmy Smith for field work in the late Ediacaran of Nevada in spring 2016, as well as Namibia in the summer of 2016. Sarah continues to participate in NMNH outreach activities, including docent teaching sessions covering Ediacaran fossils and early complex life on Earth.
Progress continued on a research project on the late Ediacaran of Namibia, initiated in 2014. Marc Laflamme, Sarah Tweedt, Erwin post-doc Simon Darroach and other students completed a month of fieldwork in southern Namibia, acquiring a large amount of stratigraphic and paleontological data; several new localities were discovered. Another field season is planned for 2016. One paper from this project was published this year (Darroch et al. 2015); others are in review or in preparation.
Prof. Ariel Chipman of the Hebrew University of Jerusalem spent a year as a sabbatical visitor in Paleobiology at the National Museum of Natural History. The main objective of his visit was to gain a better knowledge and understanding of the early arthropod fossil record, through a detailed reading of the relevant literature and examining the Burgess Shale collection. Prof. Chipman synthesized the data available from the fossils with his knowledge and experience of arthropod development. The outcome of this synthesis was a paper reconstructing hypothetical patterns of development in key fossils along the arthropod phylogeny. This paper has now been published in BMC Evolutionary Biology.
In Oct 2015 Dr. Emmy Smith moved to NMNH and joined this project. Emmy received her Ph.D in 2015 with Francis Macdonald at Harvard working on late Ediacaran and early Cambrian stratigraphy, geochemistry, geochronology and paleontology. Erwin secured Smithsonian funding for her post-doc. Smith has been developing a field project in the western US late Neoproterozoic.