Macroevolutionary patterns and processes
Curator Bruce S. Lieberman's entire career has been dedicated to the study of the patterns and processes of macroevolution using the fossil record. He was taught by the three leading figures of macroevolution: his undergraduate advisor was Stephen Jay Gould at Harvard College, his graduate advisor was Niles Eldredge at Columbia University and the American Museum of Natural History, and his first post-doctoral advisor was Elisabeth Vrba at Yale University. Bruce's research focuses on the role climate change and abiotic factors play in driving evolution and extinction, the nature of evolutionary radiations, how and why rates of evolution vary through time, the dynamics of mass extinctions, mechanisms of evolutionary stasis and punctuated equilibria, phylogenetics, and biogeography. Work in his lab has also pioneered the application of Geographic Information Systems (GIS) and Ecological Niche Modeling (ENM) to the study of the fossil record, emphasizing biogeographic and evolutionary patterns in deep time. Various projects in this area include work with former students and post-docs Luke Strotz, Erin Saupe, Corinne Myers, Alycia Stigall, and Jonathan Hendricks documenting:
the important role that physiology plays in mediating macroevolution, https://royalsocietypublishing.org/doi/full/10.1098/rspb.2018.1292 ;
how species niches are conserved over millions of years, https://royalsocietypublishing.org/doi/10.1098/rspb.2014.1995 ;
the relative roles that niche breadth and geographic range play in determining long term species survival, https://onlinelibrary.wiley.com/doi/abs/10.1111/geb.12333 ;
and the dire threats our marine biota faces in the near future due to changing climate, https://onlinelibrary.wiley.com/doi/full/10.1111/jbi.12289 .
In addition, this work has demonstrated the overwhelming role that abiotic factors, as opposed to competition, play in determining long term species survival, https://royalsocietypublishing.org/doi/full/10.1098/rspb.2010.1617 ,
the role that invasive species played in mediating the Late Devonian biodiversity crisis, https://www.sciencedirect.com/science/article/pii/S0031018204003001 ,
and the paleobiogeography of the distinctive creatures found in the Burgess Shale, https://www.sciencedirect.com/science/article/pii/S0031018208002162 .
Large-scale Patterns in the History of Life
As part of Lieberman's research interests in macroevolution and biogeography, one of the topics he has considered is the evidence that at the large scale physical factors play a fundamental role in influencing macroevolution. This has included investigating the evidence that there is a significant coupling between carbon dioxide levels and rates of macroevolution. In addition, Bruce along with former student and emeritus University Professor of Mathematics at Iowa State University James Cornette investigated the extent to which the history of Phanerozoic diversity can be modeled as a random walk and found strong evidence that except for the last 75 million years marine animal diversity and origination largely follows a trajectory indistinguishable from a random walk. This does not mean that the history of diversity over the last 520 million years is random, and instead it may be that diversity is largely tracking environmental variables that themselves are following a random walk pattern. More recently, and associated with his work in the area of astrobiology described above, he has been collaborating with Adrian Melott to help demonstrate that there are large scale cycles in the fossil record of biodiversity, origination, and extinction operating on the order of ten’s of millions of year click here to read the article describing this research. Lieberman and Melott have also identified how volatility is a key trait uniting things as diverse as fossil species, stock prices, and the birth and death of stars in our universe. Each of these findings indicates that although the history of life is governed by contingency, this contingent system also shows predictable patterns.
Work in Bruce S. Lieberman's lab has also considered the theory of evolutionary radiations (discussed below) and the Red Queen hypothesis: https://royalsocietypublishing.org/doi/full/10.1098/rsbl.2017.0734
Curator Bruce Lieberman has an interest in paleobiogeographic studies and this has formed an important component of his research. This research has involved phylogenetic approaches, Geographic Information Systems (GIS) and Ecological Niche Modelling (ENM) to study biogeographic patterns in deep time using the fossil record.
This research has also included applying Geographic Information Systems (GIS) and Ecological Niche Modeling (ENM) to study biogeographic patterns in deep time using the fossil record. Some of this work was done in conjunction with Lieberman's former student Alycia Stigall, who is now a professor at Ohio University, and involved exploring ecology and evolution during the Late Devonian biodiversity crisis. Other research with her and his former postdoc Jon Hendricks involving a GIS based analysis of paleobiogeographic and evolutionary patterns in Cambrian Burgess Shale type faunas is figured above.
Lieberman's lab has also been very interested in using GIS to explore the role that competition plays in influencing macroevolution. His former student Cori Myers and he conducted a GIS based analysis of the charismatic marine vertebrate fauna of the Cretaceous Western Interior Seaway. Their results suggest that in the Cretaceous, and perhaps in general at the grand scale of the history of life, environmental factors played a much more prominent role in structuring geographic distributions, and causing extinction, than interspecific competition.
Lieberman has used phylogenetic patterns in trilobites to consider several macroevolutionary phenomena. For instance, he has studied the nature of the Cambrian radiation and rates of evolution during this key time period in the history of life.
Lieberman was funded by NSF, through their RevSys program in Systematic Biology, to investigate phylogenetic patterns in a diverse clade of phacopid trilobites, the cheirurids. He used phylogenies to produce a stable, modern classification for the group, and to understand biogeographic patterns and macroevolution in this major invertebrate clade. This included a consideration of patterns of speciation and extinction during a key episode in the history of life, the Late Ordovician mass extinction. He worked closely with former students Curtis Congreve and Wes Gapp to produce a phylogenetic hypothesis for the Deiphonine trilobites, a subfamily of Cheiruridae and conducted a biogeographic analysis on the group. This work has been published in the Journal of Paleontology. They have also produced a phylogenetic hypothesis for the Sphaerexochinae and the Eccoptochilinae. We have also investigated phylogenetic patterns in a closely related group of trilobites, the Homalonotidae. These have a different life history strategy than many cheirurids and also occupy different environments. Thus they provide an excellent point of comparison to consider macroevolutionary patterns and processes and how these may vary among trilobite groups.
Along with former student Francine Abe he also considered tempo and mode of evolution during what is often termed an adaptive radiation of trilobites during the Devonian. They determined this radiation was not governed by adaptive factors but instead was driven by the complex geography of the region the trilobites occurred in. This work helped Lieberman to develop a macroevolutionary view of evolutionary radiations, which showed that adaptive radiations are only one type of radiation, abiotic factors rather than adaptation are more likely to have caused most radiations, and exaptation, species selection, and the Turnover Pulse hypothesis are all phenomena that need to be incorporated into the literature on evolutionary radiations. This work also culminated in a paper that appeared in Trends in Ecology & Evolution (TREE).
Lieberman has used phylogenetic biogeographic approaches to determine the relationship between earth history change and evolution and also to reconstruct the sequence of Paleozoic tectonic events. One of the time intervals his research has focused on is the Cambrian radiation: that key episode in the history of life when diverse, abundant animal remains appear in the fossil record. He has conducted phylogenetic analyses of the diverse olenelline trilobites and used these to study evolutionary and biogeographic patterns during the radiation.
Phylogenetic and biogeographic patterns suggest that the radiation of trilobites may have been underway in the late Neoproterozoic before the group becomes manifest in the fossil record; these patterns also suggest that the breakup of a supercontinent at the end of the Neoproterozoic had an important effect on the topology of the Cambrian radiation. He has also used probabilistic models to study how fast the rates of evolution were during this interval and the results suggest that rates of evolution were high at the time but not so high that new rules of evolution need to be invoked to explain the Cambrian radiation.
This research has been supported by the National Science Foundation and the National Geographic Society and has involved fieldwork in the Mackenzie Mountains, Northwest Territories, Canada.
With support from the National Science Foundation Lieberman studied evolutionary and biogeographic patterns in a Middle Cambrian softbodied fauna from Utah. This work was conducted with his former postdoc, Jon Hendricks. They described new taxa from these localities and have also conducted phylogenetic analyses on a series of new arachnomorph taxa that have been recovered from these localities. In addition they conducted biogeographic studies on these taxa using phylogenetic biogeographic analyses and Geographic Information Systems (GIS), the latter in conjunction with Alycia Stigall at Ohio University. Finally, they documented beautifully preserved jellyfish from the Middle Cambrian of Utah. These appear to represent modern crown groups, including modern orders, families, and in one case a genus. He has continued work on faunas of this age, specifically the radiodontans, with Allison Daley and Stephen Pates.
Taxonomy, Taphonomy and Paleoecology of soft-bodied organisms
Research Affiliate Julien Kimmig studies soft-bodied organisms in Burgess Shale-type deposits. His research focuses on the preservation mechanisms, as well as the diversity of these deposits. Current projects focus on the Rockslide Formation in the Mackenzie Mountains of Canada, the Spence Shale in Utah and Idaho, and the Pioche Formation in Nevada.
In collaboration with Adrian Melott and other scientists, and with support from NASA, Lieberman conducted research investigating the nature of the late Ordovician mass extinction and the extent to which it may have been precipitated by a Gamma Ray Burst. This research is described more fully at http://kusmos.phsx.ku.edu/~melott/Astrobiology.htm