Scott Lidgard
Field Museum, Integrative Research, Department Member
Previous analyses of evolutionary patterns, or modes, in fossil lineages have focused overwhelmingly on three simple models: stasis, random walks, and directional evolution. Here we use likelihood methods to fit an expanded set of... more
Previous analyses of evolutionary patterns, or modes, in fossil lineages have focused overwhelmingly on three simple models: stasis, random walks, and directional evolution. Here we use likelihood methods to fit an expanded set of evolutionary models to a large compilation of ancestor-descendant series of populations from the fossil record. In addition to the standard three models, we assess more complex models with punctuations and shifts from one evolutionary mode to another. As in previous studies, we find that stasis is common in the fossil record, as is a strict version of stasis that entails no real evolutionary changes. Incidence of directional evolution is relatively low (13%), but higher than in previous studies because our analytical approach can more sensitively detect noisy trends. Complex evolutionary models are often favored, overwhelmingly so for sequences comprising many samples. This finding is consistent with evolutionary dynamics that are, in reality, more complex...
Research Interests:
We argue that the mathematization of science should be understood as a normative activity of advocating for a particular methodology with its own criteria for evaluating good research. As a case study, we examine the mathematization of... more
We argue that the mathematization of science should be understood as a normative activity of advocating for a particular methodology with its own criteria for evaluating good research. As a case study, we examine the mathematization of taxonomic classification in systematic biology. We show how mathematization is a normative activity by contrasting its distinctive features in numerical taxonomy in the 1960s with an earlier reform advocated by Ernst Mayr starting in the 1940s. Both Mayr and the numerical taxonomists sought to formalize the work of classification, but Mayr introduced a qualitative formalism based on human judgment for determining the taxonomic rank of populations, while the numerical taxonomists introduced a quantitative formalism based on automated procedures for computing classifications. The key contrast between Mayr and the numerical taxonomists is how they conceptualized the temporal structure of the workflow of classification, specifically where they allowed meta-level discourse about difficulties in producing the classification.
Research Interests: Systematics (Taxonomy), Philosophy of Science, Philosophy of Biology, Systematic Biology, History of Science, and 9 moreClustering and Classification Methods, History of Biology, Logical Positivism, Logical Empiricism, Cladistics (Systematic Biology), Ernst Mayr, Numerical Taxonomy, Classification, and History of Mathematization
Tectonic displacement and small-scale tsunamis apparently affected deposition of the Kolymbia limestone, Cape Vagia, Rhodes, Eastern Mediterranean. Coarse beds interrupt the sequential build-up of this Pliocene–Pleistocene bryomol... more
Tectonic displacement and small-scale tsunamis apparently affected deposition of the Kolymbia limestone, Cape Vagia, Rhodes, Eastern Mediterranean. Coarse beds interrupt the sequential build-up of this Pliocene–Pleistocene bryomol limestone. Celleporid bryozoans, bivalves, and brachiopods dominate these beds. The palaeoecology of the thicket-forming Celleporaria palmata is re-evaluated and subsequently revised. The limestone comprises two parasequences in a transgressive systems tract, and deposition occurred at palaeodepths between 30 and 120 m. At intervals, tectonic movements lowered relative sea level and sent slumps of shallow-water fauna downslope. The depositional history was validated using independent sets of data: sediment structure and grain size, palaeobathymetry using bryozoan growth forms and occurrences of modern representatives of bryozoans and other taxa, basin configuration, and regional tectonics. Concordance of these lines of evidence provides a means of evaluating confidence in palaeoenvironmental inferences.
Research Interests:
Although the pattern of the early angiosperm radiation has been substantially clarified by palaeobotanical and stratigraphic investigations over the last 30 years1-3, knowledge of associated vegetational and floristic change remains... more
Although the pattern of the early angiosperm radiation has been substantially clarified by palaeobotanical and stratigraphic investigations over the last 30 years1-3, knowledge of associated vegetational and floristic change remains limited. Quantitative analyses of Cretaceous fossil floras indicate that by ~90 million years before present (BP) angiosperms had achieved widespread floristic dominance, at least in the Northern Hemisphere. Although some
Research Interests:
The latitudinally diachronous appearance of angiosperm pollen during the Cretaceous is well documented, but the subsequent diversification and accompanying significant changes in floristic dominance have not been assessed quantitatively... more
The latitudinally diachronous appearance of angiosperm pollen during the Cretaceous is well documented, but the subsequent diversification and accompanying significant changes in floristic dominance have not been assessed quantitatively for a wide range of paleolatitudes. Trend surfaces fitted to within-palynoflora diversity data from 1125 pollen and spore assemblages show that angiosperms first become floristically prominent in low paleolatitude areas( approximately 20 degrees N to 20 degrees S). Non-magnoliid dicotyledons show a similar but slightly delayed pattern of increase and are the principal component of angiosperm diversity from all areas sampled. Monocotyledons and magnoliid dicotyledons are significant primarily in low to middle paleolatitude palynofloras( approximately 50 degrees N to 20 degrees S) during the latest Cretaceous. As angiosperms become increasingly prevalent the importance of most non-angiosperm taxa either decreases or remains unchanged. The only apparent exception is a striking increase in gnetalean diversity concurrent with the initial angiosperm diversification at low paleolatitudes.