Michael Foote - US grants

Several intriguing hypotheses have been proposed regarding large-scale temporal patterns of morphological diversity in the history of clades, particularly those originating in the early Paleozoic. However, the testing of evolutionary hypotheses regarding diversity has either used taxonomic diversity as a proxy for morphological diversity, or focused on patterns at relatively small scales. The proposed research will investigate temporal patterns of morphological diversity in large clades of Paleozoic echinoderms, Class Crinoidea, as well as in smaller clades. Specifically, it will be determined whether morphological diversity is concentrated early in the history of a clade, and whether there are temporally directed differences between morphological and taxonomic diversity. Morphological diversity will be measured directly, using dissimilarity measures based on discrete-character data. These data will be collected from published species descriptions as well as museum specimens. The approach adopted for quantifying morphology will allow direct documentation of morphological diversity patterns at a broader taxonomic scale than has heretofore been practiced, and will therefore provide important new data relevant to major questions of interest in evolutionary biology.

Foote 9506568 This research will (1) use explicit data on skeletal anatomy to document evolutionary radiations in Paleozoic and Mesozoic crinoids, and (2) test for a proposed difference between evolutionary radiations at different taxonomic scales by comparing the radiation of crinoids as a whole to the radiations of the constituent subgroups of crinoids. Evolutionary radiations, involving substantial increases in the number of named taxa and in morphological diversity, are among the most prominent features of the fossil record. It is commonly thought that evolutionary radiations at different taxonomic, temporal, and spatial scales do not differ significantly in temporal patterns or underlying mechanisms. This perspective has scarcely been tested directly. There are some hints that there may be a major difference between the evolutionary radiations of higher taxa (clades) and the lower taxa (subclades) nested within them, namely that morphological diversification within subclades is more gradual in time than diversification of the larger clade to which they belong. However, these suggestions have been based on case studies that are not ideally suited to test this idea. By comparing the Paleozoic radiation of a major invertebrate group, the Crinoidea, to that of subsidiary crinoid clads that diversified concurrently with the larger crinoid clade, I will test for the existence of such a discordance between taxonomic ranks. The Mesozoic radiation of articulate crinoids will provide an additional comparison. The results will help to answer questions about the hierarchical nature of evolution and our ability to predict larger-scale evolutionary patterns from smaller-scale patterns. Changes in morphological diversity, or disparity, during evolutionary radiations are usually assessed by using proxies such as the number of higher taxa (mainly classes and orders). There are a number of reasons to question the adequacy of such proxies. The proposed research will use direct quantification o f morphology to study evolutionary radiations in crinoids. I will use discrete morphological characters to quantify crinoid form, and will measure morphological disparity based on the net dissimilarities among species. I will apply a number of quantitative approaches, including "clade-shape" statistics, to explore the temporal pattern of morphological expectations of various evolutionary models. The proposed research will answer questions about the generation of morphological diversity over long spans of evolutionary time, and will develop a morphological database that can be used by other workers to investigate a wide range of issues, including phylogenetic relationships, evolutionary rates, and trends.

9801607 Foote The origin of the seed in the Late Devonian was a key innovation that facilitated the exploitation of a wide range of terrestrial environments and diverse ecological strategies during the early evolution of plants on land. Throughout the late Paleozoic, seed plants radiated in environments with ecological dynamics and organization that were fundamentally different from those of the Recent, most notably in the absence of tetrapod herbivory, limited direct plant-insect interactions, and strong phylogenetic partitioning of ecological strategies among different plant groups. The fossil seed record of the late Paleozoic provides an opportunity to study how increasing complexity and modernization of ecological interactions was reflected in structural adaptations to protect and disperse propagules. The research proposed here includes analyses of taxonomic diversity and morphological disparity in subclades of late Devonian to Permian fossil seed plants. The evolutionary significance of seed size will be examined by testing for trends in volume. A morphospace based on seed morphology will be used to test hypothesized patterns of morphological and ecological overlap among seed plant subclades. This research will be the first quantitative treatment of macroevolutionary patterns during the early history of a major group of land plants and will contribute to understanding of the unique structure of late Paleozoic terrestrial ecosystems.

This project explores the manner in which morphology has evolved over the course of the 40 million year history of the deep-sea ostracode genus Poseidonamicus. Fossil and modern specimens will be studied using scanning electron microscopy. Features of the ostracode carapace will be measured using the digital images obtained, and patterns of morphological change over time will be reconstructed. From these data, it will be determined if features that are more variable within populations are also more likely to evolve.

This study will be one of the first to use the fossil record to determine if patterns of variation affect the direction of long-term evolutionary change. While the evolutionary importance of these patterns is well understood over the course of a few generations, it is not clear whether trait variability matters for long-term evolution. Several researchers have suggested that patterns of variation should act to bias or constrain the course of evolution, even over long time stretches of time. The proposed research uses the evolutionary history of a taxon with a rich fossil record to test these suggestions.

ABSTRACT

Diversity Dynamics of Middle Paleozoic Marine Animals

Michael Foote
EAR-0105609

The subject of diversity dynamics explores how and why the number of species in the world changes over time. This research will explore diversity dynamics with data on marine animals from the middle of the Paleozoic Era, about 440 to 350 million years ago. The species composition of fossil communities will be inventoried, and the ancient geographic and environmental setting of these communities will be determined. Using this new information as well as existing data from other sources, the times of origination and extinction of animal genera (the more inclusive taxonomic units that consist of one or more related species) will be estimated. This will allow the temporal patterns of diversity, origination, and extinction to be reconstructed, and these temporal patterns in turn will be used to assess the dynamics of diversity. When diversity increases over millions of years, does this tend to occur because the rate of production of new species has increased or because the rate of extinction of existing species has decreased? Likewise, does a decline in diversity tend to be marked by a decrease in origination or an increase in extinction? In other words, is origination or extinction more important in regulating biological diversity? Previous research shows that the style of diversity dynamics changes over the course of animal evolution, with extinction more important for about the first 300 million years of the history of animals (during the Paleozoic Era) and origination more important thereafter (during the Mesozoic and Cenozoic Eras). There are reasons to think that diversity dynamics may vary geographically and environmentally. This research will be the first to test the predictions that, as far as diversity regulation is concerned, extinction is more important in the tropics than in the temperate zones and more important in shallow-water environments than in deeper waters. In addition, it is known that shallow marine and tropical marine environments were more prevalent in the Paleozoic Era than later. The results of this research will therefore be significant in determining whether the observed, long-term temporal change in diversity dynamics may be underlain by a change in the prevalence of certain environmental and geographic settings in the marine realm.

Non-technical abstract: Dissertation Research: Morphological
diversification of anostomimorph and curimatimorph fishes.

Why is biodiversity distributed unequally across the tree-of-life? Some
groups of species have evolved extraordinary anatomical variation while
other groups contain many species that look and act similar. To begin to
understand how and why the general phenomenon of unequal diversification
occurs, this research will investigate how and why a specific lineage of
South American fishes related to piranhas and tetras evolved an anatomical
diversity very much greater than that of the lineage of its closest
relatives. This case study is rare and valuable because it approximates a
naturally controlled experiment. Because the two groups of fishes contain
equal numbers of species, share a recent common ancestor (and therefore
began to evolve independently at the same time) and live together
throughout tropical South America, the differences in their diversities
cannot be explained by differences in net speciation rate, age, or
environmental effects. The removal of these factors leaves at least two
potential explanations of the observed differences in diversity. The
differences may be due to random evolution, or an intrinsic feature of
anatomy or ecology shared only by the more diverse group may promote the
evolution of new morphologies. This research program will investigate
these two alternatives by 1) using a detailed anatomical study to
reconstruct the genealogical relationships, or "trees-of-life" for these
fishes, 2) measuring the anatomical differences between these species from
an extensive series of x-ray images and 3) performing a novel analysis that
combines the measurements of anatomical differences and trees-of-life with
computer simulations of evolution. This analysis will test whether
diversities as different as those observed could have evolved randomly. If
the analysis were to reject the hypothesis of random evolution, then it
would be likely that an intrinsic difference drove one group to diversify
greatly while the other did not. If the second alternative is supported,
this project will identify the anatomical and ecological features most
likely to have catalyzed the evolution of novelties in the more diverse
group. Future studies can then test whether the evolution of similar
properties in other groups of organisms generally promotes the genesis and
maintenance of biodiversity.

In a broad sense, this study will help reveal why biodiversity is not
distributed equally across the tree-of-life for all organisms. The methods
developed for use in this project are transferable to studies of a wide
variety of other organisms and will be made freely available via the
Internet. This project will also promote international collaboration on the
study of an important group of tropical fishes valued as food throughout
South America, prized for their ornamental beauty worldwide and that serve
important ecological roles as part of the most species-rich freshwater fish
fauna in the world. Current and potential collaborations include work on
the discovery and description of new species, the building of natural
history collections in the United States and in South America, and
conservation biology. Results from this work also fuel a continuing
dialogue about biodiversity with students and museum visitors through a
series of exhibits and public presentations.

Numerical and experimental geodynamo models offer complementary insights into the dynamics of the Earth's liquid iron core. The goal of this research project is to leverage the strengths of both approaches to gain significant insights into the origin and evolution of the Earth's magnetic field. The experiments produce geophysically realistic turbulence in liquid metal flows that are well beyond the spatial resolution of direct numerical simulations. Experimental observations of highly nonlinear interactions between the flow and the magnetic field provide unique information about the complexity of important processes in the core. Parallel advances in computation have produced increasingly sophisticated models for unresolved (subgrid-scale) turbulence. These models have been implemented and tested in numerical geodynamo calculations with remarkable success. However, the effort to push these models to Earth-like conditions is presently hampered by the lack of "known" solutions to test the predictions of the subgrid-scale models. Use of carefully chosen diagnostics from the experiments enables more realistic tests of the numerical models. The models, in turn, aid the interpretation of the experiments, which establishes a foundation for refining the assumptions used in the construction of the subgrid-scale models. This synergy between computations and experiments is most effectively realized through a collaborative research program.

The experiments used in this study include spherical Couette flow and rotating thermal convection. In either case, an externally imposed magnetic field interacts with the liquid metal flow. The experimental setups are based on prior experience with the explicit goal of producing distinctive large-scale flows that are sensitive to the presence of turbulence. Experimental observations of these large-scale features are used to test the predictions of the numerical models. Spherical Couette flow permits strong (and realistic) interactions between the flow and the magnetic field. Three of the four key subgrid-scale models in the geodynamo problem are being tested under the conditions of rapid rotation and strong magnetic fields by measuring the pattern of induced magnetic field outside the liquid metal. Rotating convection experiments, with and without an imposed magnetic field, are being used to test the fourth subgrid-scale model. The primary observations in the convection experiments include the total heat flow, the large-scale velocity and the power spectra of temperature fluctuations. The expected outcome of this research project is a more realistic geodynamo model that incorporates sophisticated parameterizations for turbulence and a database of experimental results to stimulate other research groups to engage in similar comparisons using different modeling strategies.

Intellectual Merit: Two- and three-dimensional numerical models of phase separation and hydrothermal circulation will be developed for the Main Endeavour Field (MEF) on the Juan de Fuca Ridge. The models will integrate available vent fluid temperature, salinity, and heat flow data, along with all other relevant constraints, such as magma lens geometry and depth, extrusive layer thickness, and vent field area. A particular goal is to understand the reason for the southwest to northeast gradients in temperature and salinity across the MEF. In addition to developing a quasi-steady state circulation model that represents the behavior of the MEF between 1988 and 1995, the available data will be used to model the response of the system to the magmatic event of 1999, and what appears to be the decline in hydrothermal heat output since that time. Preliminary modeling shows that vent temperature, salinity and heat output are controlled primarily by crustal permeability distribution and the bottom boundary conditions, which control the temperature and areal extent of the two-phase zone at depth. The research program involves three inter-related tasks: (1) the development of 2-D single-pass models in order to match southwest to northeast temperature and salinity gradients across the MEF; (2) the development of 2-D models involving dike emplacement to understand the response to the 1999 event and the subsequent system decline; (3) the development of 3-D single pass single phase and two-phase models of hydrothermal circulation that includes the effect of induced circulation in layer 2A, constrained by all available heat flow data. These will be the first 2- and 3-D numerical models of phase separation for a mid-ocean ridge hydrothermal system and the first numerical models for a particular vent field that are constrained by time series data of vent temperature, hydrothermal heat output, and vent salinity. These will also be the first fully numerical models of phase separation and hydrothermal circulation of a NaCl-H2O fluid near a dike. Finally, the results will provide important insights into how a major hydrothermal system decays in time. The results of this modeling will thus provide important insights into the process of phase separation in seafloor hydrothermal systems and provide constraints on the permeability structure of the ridge axis. The results will help determine whether the decay of hydrothermal heat output is controlled by magmatic crystallization and cooling at depth or by the evolution of crustal permeability.

Broader Impacts: Although these models will be specific to the MEF, the results will lead to increased understanding of phase separation and hydrothermal circulation at mid-ocean ridges, which is a broad field of interdisciplinary study. The development of the 3D two-phase code FISHES will become an important community tool for hydrothermal modeling. The 2-D and 3-D versions of FISHES, and a user's manual, will be placed on the PIs' personal websites when they are available for general use. This research will train a new graduate female student in an important area of interdisciplinary research and train the student in the use of numerical codes. The research will also advance the scientific development of a young female researcher. The results of this research will be incorporated into courses on fluid processes taught at the university level.