NAPC 2001

Abstracts, Ja - Ju
(5/17/01)

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INVASIVE SPECIES, EXTINCTIONS, AND THE FOSSIL RECORD

JABLONSKI, David, Dept. of Geophysical Sciences, University of Chicago, Chicago, IL, USA; Kaustuv Roy, Section of Ecology, Behavior and Evolution, Div. of Biology, University of California San Diego, La Jolla, CA, USA; and James W. Valentine, Dept. of Integrative Biology, University of California, Berkeley, CA, USA

Biotic interchanges and invasive species represent a major threat to present-day biodiversity. The fossil record is rich in biogeographic dynamics across a variety of scales and driving mechanisms, from range shifts in response to climate change to extinction-mediated biotic interchanges. E.g., understanding biogeographic responses to changing climates is essential for predicting the consequences of regional and global environmental change. Our data on the Pleistocene and modern range limits of Californian marine bivalves show species that significantly shifted their geographic ranges in response to Pleistocene glacial-interglacial cycles were preferentially drawn from the large end of the provincial body size-frequency distribution. This difference is not due to phylogenetic effects, or differences among major ecological categories (life position, trophic group, larval mode). The same size-selectivity can be seen for invasive species of bivalves in present-day marine environments, despite the different mechanism of range expansion. These results indicate that range limits of large-bodied bivalve species are more volatile than small-bodied ones, and that body size and its correlates need to be considered when predicting the responses of marine communities to climate change, biotic interchanges, and human-mediated invasions. At larger scales, interchanges among regions tend to be asymmetrical, with recipient regions often suffering greater pre-invasion extinction than donors. This strongly supports a role for ecological incumbency, although interregional contrasts in physical environmental changes cannot always be ruled out. However, after the K-T mass extinction North America was subject to more intense invasion than other regions despite its unexceptional (if severe) extinction. This response implies a nonlinear relation between extinction and invasion intensities, or simply a threshold above which the relation breaks down. This result may have important implications for the persistence and recovery of local biotas and intrerregional source-sink dynamics.

FISH STORIES: USING FOSSILS FOR FISHERIES MANAGEMENT

JACKSON, Jeremy B.C., Scripps Institution of Oceanography, University of California, San Diego, CA, USA

Fossil time series can provide a baseline of the characteristic variance of marine ecosystems prior to human disturbances and the sequence of subsequent changes. However, fossil data alone can be misleading, and archeological, historical, and ecological data are required to sort out cause and effect. I present three examples of the application of paleontological data to fisheries. Abundance of fish scales in annually varved, hypoxic sediments of Santa Barbara Basin demonstrate enormous, cyclical variations in anchovies and sardines over several thousand years due to regime shifts in oceanogaphic conditions. Studies of the possible impacts of fishing must incorporate this extreme natural variability. The second example concerns mass mortality of Caribbean reef corals due to disease and overfishing. Surveys of Pleistocene reef terraces and drilling of subtidal Holocene reefs demonstrate great stability of coral community composition until the 1970s. There is also paleontological and ecological evidence of unprecedented replacement of formerly abundant, competitively dominant coral species by more tolerant weedy species. However, the fossil record is so far silent about the occurrence of disease and overfishing that set off the coral decline. The final example concerns eutrophication of Chesapeake Bay. Sediment accumulation, organic carbon, and pollen in cores demonstrate massive increases in sedimentation following the advent of European agriculture in the mid 18th century. Ratios of planktonic to benthic diatoms increase and records of submerged aquatic vegetation decrease in tandem. However, eutrophication and hypoxia did not occur for another 100 years when oysters were extirpated by mechanical dredging. Formerly abundant oysters had filtered the equivalent water of the entire Bay every few days and suppressed the build-up of phytoplankon. Thus, eutrophication and hypoxia were due more to loss of "top-down" control of phytoplankton by oysters than to "bottom-up" nutrification—with profound implications for ecosystem restoration and management.

EVOLUTIONARY COMPUTING WITH SWARMS

JACOB, Christian, Dept. of Computer Science, University of Calgary, AB, Canada

Swarm intelligence systems are attracting more and more attention as convenient models to investigate patterns of emergent behaviors. Swarm systems provide object-based, parallel models that evolve behavior patterns from massively parallel, but local interactions of, usually simple, agents. An ant colony is a typical example of such a swarm system. Each ant follows a rather restricted set of rules through which it interacts with its environment. However, an ant colony, as a collection of thousands of ants, acts like a multicellular organism of its own, a super-organism that develops, evolves, and derives its emergent behavior from an intricate and massively-parallel set of interactions among the individual members of the colony.

Apart from interaction patterns among social insects (ants, termites, bees, etc.), similar principles of self-organization, emergent complexity, cooperation and competition arise in gene regulation networks, in the formation of cell clusters during development, in signal propagation within neural networks, in ecosystems, in co-evolutionary scenarios, and in any social and economic system.

Evolution is the key designer of swarm behaviors in nature, as, for example, many studies on social insects have shown. Therefore, it is desirable to combine evolutionary models with swarm systems, which will allow for more realistic investigations of the interconnections between principles of evolution and massively parallel, decentralized systems.

We will present a framework for performing experiments in evolutionary computing, as well as swarm intelligence systems. The combination of both approaches into evolutionary swarm systems poses major challenges (both from a computational and a conceptual point of view). We will outline the difficulties and discuss simple examples of evolutionary swarms, in particular in the context of social insects and plant ecosystems.

OPERATIONAL AND BIOLOGICAL REASONS WHY
MOLECULAR RATES ARE EXPECTED TO VARY

JACOBS, David K., Dept. of Organismic Biology, Ecology, and Evolution, University of California, Los Angeles, CA, USA

Following the lead of Linus Pauling and Matsutoshi Nei many have employed an assumption of a molecular clock combined with statistical methods to extrapolate from known tie points in the fossil record to infer divergence times. However, there are aspects of taxon sampling that influence sequence alignment and phylogeny reconstruction—steps that are required to calculate rates. Such imbalances between well samples clades used to infer rates and less well sampled outgroups should lead to systematic biases most frequently resulting in erroneously large basal branch lengths. In addition to such operational issues, recent work relating genome size to deletion processes that eliminate DNA suggest that genome size and molecular rate covary. Other aspects of genome structure and process such, as GC content, gene duplication, inversion frequency and DNA repair mechanisms would also be expected a priori to influence rates of molecular change in different lineages. All of the above should influence the calculation of rates and divergence times based on suites of proteins—the approach that has recently been popularized for calculations of divergence times of various metazoan groups. However, protein rates are summations over broad suites of amino-acid sites that are each subject to a different degree of selective constraint. This is a far cry from the molecular clock processes suggested by Nei based on sets of neutral alleles. However, even sequences that are presumed to be selectively neutral are seen to vary by a factor of two in intraspecific phylogeographic trees. Apparently, aspects of local metapopulation structure can also strongly influence molecular rates in "ideal" unsaturated data. Given the above arguments calculations of divergence times should be treated with circumspection by workers interested in reconstructing the history of life.

TESTING HETEROCHRONY IN THECIDEIDE BRACHIOPODS BY INTEGRATING PHYLOGENETIC, SCLEROCHRONOLOGIC AND MORPHOMETRIC DATA

JAECKS, Glenn S., Sandra J. Carlson, and Howard J. Spero, Dept. of Geology, University of California, Davis, CA, USA

Thecideida (Triassic-Recent) is an order of small-bodied, cemented, tropical to subtropical cave-dwelling brachiopods that have an unique brachidial (dorsal median septum) morphology. Thecideide brachiopods have been considered a paedomorphic taxon because of their relatively small body size and simple, circular lophophore. Phylogenetic results of 48 ingroup taxa previously presented support thecideide monophyly, and suggest a complex mosaic of paedomorphic and peramorphic patterns within thecideide evolution. Oxygen stable isotope sclerochronology of extant genera, Thecidellina and Lacazella, suggests that thecideides have much shorter longevities (1­3 years) than possible sister taxa, including terebratulides, strophomenides (10 or more years) and spire-bearers. This suggests that a strong component of progenesis is likely responsible for their small size. Thecideide median septum morphology is highly varied, from simple, blade-like structures to broad, three-dimensional branching structures; lateral septa may also be present. I describe median septum development and evolution using geometric morphometric analysis of median septum outline landmarks. I am testing apparent patterns of peramorphosis in median septum evolution by combining sclerochronological with morphometric data to produce calibrated ontogenetic trajectories, all evaluated in a phylogenetic context. One such peramorphic pattern appears within a clade including the extant Thecidellina and extinct Moorellina: three Moorellina species as adults display a pair of posterior processes normal to the median septum, whereas Thecidellina has these features as a juvenile only. As Thecidellina is derived relative to Moorellina, this may be a case of peramorphosis. Other possible cases of peramorphosis appear within the other extant clade including Lacazella and Pajaudina, in which multiple median septum ramuli are derived several times. Ramuli are associated with folds in the lophophore that increase surface area, and their evolution may be indicative of either increased size or extended development, or both.

THE ORIGINS AND EVOLUTION OF THE NORTH AMERICAN GRASSLAND BIOME: THE STORY FROM THE HOOFED MAMMALS

JANIS, Christine M., Dept. of Ecology and Evolutionary Biology, Brown University, Providence, RI, USA; John Damuth, Dept. of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA, USA; and Jessica M. Theodor, Dept. of Organismic Biology, Ecology and Evolution, University of California, Los Angeles, CA, USA

The North American grassland biome first appeared around 18 Ma in the mid Miocene. The familiar story of the Neogene evolution of this biome is of the replacement of browsing (leaf-eating) ungulates (hoofed mammals) by more derived grazing ungulates. However, new data show a more complicated pattern of faunal succession. There was a maximum taxonomic diversity of ungulates at 16­14 Ma, including a large number of grazers, and the subsequent decline in overall diversity was largely due to extinctions among the browsers, with little corresponding increase in the numbers of grazers. Additionally, the mid Miocene faunas (18­12 Ma) contained a much greater number of browsers than any comparable present-day habitat. These non-analogous Miocene grassland faunas may reflect greater levels of primary productivity than known today, possibly as the result of higher levels of atmospheric carbon dioxide. The proposed difference in vegetational productivity also may explain why horses radiated as the main grazers in North America, in contrast to the radiation of antelope in the Plio-Pleistocene African grasslands.

A SCRATCH CIRCLE ORIGIN FOR THE MEDUSOID FOSSIL KULLINGIA

JENSEN, Sören, and Mary L. Droser, Dept. of Earth Sciences, University of California, Riverside, CA, USA; and James G. Gehling, South Australian Museum, Adelaide, Australia

Scratch circles are sets of concentric grooves that were cut in sand or mud by a tethered object rotated by currents or waves. There are scattered reports of scratch circles from the Proterozoic to the Recent. However, the occurrences of subaqueous scratch circles have been underestimated because casts of certain scratch circles have entered the literature as cnidarian medusoids.

The most compelling example is Kullingia, a supposed medusoid with sharp and regularly developed concentric ridges. The type species, Kullingia concentrica, from the Lower Cambrian of northern Sweden, possesses several features that point to its actual origin. A few specimens preserve impressions of a segmented tubular organism centered on and conterminous with the disc. In several specimens grooves are present on more than one closely spaced level of laminated sediment. There also typically is a distinct central depression, which represents the position at which the organism was attached. That Kullingia from northern Sweden is a scratch circle was first suggested by Frank Stodt (1987; thesis, Marburg). This interpretation applies also to Kullingia concentrica from the Lower Cambrian of the Ukraine, and to purported chondrophorines from the Lower Cambrian Chapel Island Formation, Newfoundland, reported as Kullingia delicata. Kullingia occurs in close association with Ediacara-type fronds in the Lower Cambrian Uratanna Formation, South Australia. It is likely that these fronds were responsible for the scratch circles.

The Kullingia-type scratch circles discussed above all occur in basal Lower Cambrian strata deposited in storm influenced marine settings. This may represent the stratigraphic coincidence of the evolution of attached tubular or frond-like organims and low levels of bioturbation that increased likelihood of preservation. A scratch circle origin probably should be considered also for certain other simple medusoids from the terminal Proterozoic and Cambrian, such as structures described as Nimbia occlusa from the Upper Cambrian of Ireland.

LATEST CHANGHSINGIAN FOSSILS AROUND THE YUNKAI VOLCANOS OF SOUTH CHINA

JIN, Yugan, Changqun Cao, and Shuzhong Shen, Nanjing Institute of Palaeontology and Geology, Chinese Academy of Sciences, Nanjing, China

Over last two decades, selecting the global stratotype for the Permian-Triassic boundary lead to establish a set of extensively studied candidate sections. These sections provided a great deal of information with regard to the end-Permian Mass Extinction. However, most of them consist of carbonates of slope facies and thus, are often condensed in thickness and contain rare authentic shallow mariner fossils. We report here a Permian-Triassic boundary section distinct from the others in South China. As much as 400 m thick, the Talung Formation of late Changhsingian accumulated in the west of the Yunkai land, of which repeated effusion of volcanos provided a huge amount of pyroclastics. The volcanic ash from its base and top was dated as 252.4 ± 0.2 and 251.6 ± 0.1 Ma respectively and thus, this unit represents deposition less than 1 m.y. The Talung Formation consists of three parts: (1) The lower, 65 m in thickness, belongs to the Clarkina changxingensis Zone of late Changhsingian and is composed of chert and cherty shale of basinal facies. (2) The middle comprises 350 m thick cyclic beds of sandstone, siltstone with coal seams. (3) The upper belongs to the Clarkina yini Zone of latest Changhsingian and comprises 15 m thick lime mudstone and packstone. The topmost limestone is overlain by tuffaceous siltstone without other fossils but abundant bivalves Claraia. We interpret the facies change between the lower and middle as an abrupt regression, and that between the middle and upper as a rapid transgression. The regression-transgression cycle can be correlated to that at the very top of the Changhsingian at the Meishan Section disregarding a great disparity in thickness. Plant and marine fossils remain highly diverse from the uppermost Changhsingian. Calcareous sponges, framebuilders of Changhsingian reefs and a bunch of pro-reef brachiopods occur in the topmost limestone as well. These facts show that the latest Changhsingian regression-transgression had not lead to faunal and floral overturn.

HIERARCHY THEORY, EVOLUTIONARY PROCESSES, AND REEF ECOSYSTEMS—THE GLUE THAT BINDS

JOHNSON, Claudia C., Dept. of Geological Sciences, Indiana University, Bloomington, IN, USA

In an attempt to further an understanding of evolutionary processes, genealogical and ecological hierarchies are recognized in macroevolutionary studies. The genealogical line is concerned with the activity of reproduction and the ecological line with matter-energy transfer. Cretaceous reefs from Tethys are used to test whether reproduction and matter-energy transfer within a reef ecosystem can be discerned from the fossil record in order to unravel large-scale evolutionary processes.

Scleractinian corals and rudist bivalves identify the reproductive process (flow of genetic information), for species are components of only the genealogical hierarchy. Trophic levels and guild structures provide data for testing the persistence of matter-energy transfer and the ecological hierarchy. As predicted by theory, mass extinctions disrupted both the genealogical and ecological lines. Data indicate that the genealogical hierarchy was permanently altered, but the ecological line was only temporarily disrupted during the terminal Cretaceous extinction event. After the K/T event, the ecological line persisted.

Although the genealogical line changed numerous times through the Phanerozoic, the persistence of the ecological line across all mass extinction boundaries allows scientists to recognize the coherent structure of reefs, for it is the process of matter-energy transfer that remains intact and identifiable within and across mass extinction boundaries.

If data from the geological record were used to evaluate evolutionary processes, we might surmise that the preservation of trophic groups and guild structures would be more valuable than the preservation of a single species if the health of our present and future reefs were endangered.

Analysis of the reef ecosystem in the context of a theoretical framework involving distinct hierarchies allows an understanding of the persistence of the reef ecosystem through the Phanerozoic, and provides a framework for evaluating the health of future ecosystems.

MORPHOTYPING THE CRETACEOUS AND PALEOGENE LEAF FLORAS OF THE ROCKY MOUNTAIN REGION

JOHNSON, Kirk R., Dept. of Earth and Space Sciences, Denver Museum of Nature and Science, Denver, CO, USA; Peter Wilf, Museum of Paleontology, University of Michigan, Ann Arbor, MI, USA; and Scott L. Wing, Dept. of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA

Extensive fossiliferous outcrops of Cretaceous and Paleogene rocks in the Rocky Mountain region have yielded abundant and diverse plant megafossils, especially leaves, for more than a century. Unfortunately, much of the early work on these floras utilized faulty taxonomy that generated highly erroneous species lists populated by extant genera. The desire to utilize this record to assess paleovegetation, paleoclimate, diversity trends, and extinction events has led to the development of a morphotype method that allows for rapid and reproducible assessment of megafloras in advance of their phylogenetic assessment. This method assigns alphanumeric identifiers (e.g., HC105) to "holomorphotype" specimens that typify morphological categories based on their leaf architecture. Application of this methodology to very large samples (10³ to 10⁴ specimens) collected and/or censused from discrete quarries in known sedimentological facies allows for quantitative assessment of floral diversity, relative abundance structure, stratigraphic range, turnover, extinction, and leaf physiognomy. To date we have morphotyped large collections from the Hell Creek, Laramie, Fort Union, Denver, Dawson, Wasatch, Willwood, Green River, and Wind River Formations of Montana, the Dakotas, Colorado, and Wyoming. This internally consistent database has allowed us to document biogeographical variation, climate change, and patterns of plant evolution and extinction before and after the Cretaceous/Paleogene and Paleocene/Eocene boundaries.

HISTORY OF THE DOMINICAN REPUBLIC PROJECT

JUNG, Peter, Naturhistorisches Museum Basel, Basel, Switzerland

It has long been known that the northern Dominican Republic is rich in excellently preserved Neogene molluscan faunas. On the other hand, the geological map of that area looked like a white spot. For this reason, John Saunders, then micropaleontologist at the Basel Natural History Museum, and the present author sat together to plan a project. The main aim was to measure sections and to collect faunas from as many horizons as possible. At the same time it was thought essential to coordinate micropaleontological and macropaleontological evidence. The fieldwork was financed by the Swiss National Science Foundation and took place in 1978, 1979, and 1980 during a total period of three months. The first publication of the project dealing with field surveys, lithology, environment, and age appeared in 1986, and since then 20 monographs have been published in Bulletins of American Paleontology. Additional monographs are expected.