Patterns of biodiversity in the marine realm are driven by extrinsic (non-biological) processes that interact with intrinsic (biological) constraints. Together these two processes provide the basis for speciation (diversity) and extinction (resilience) that shape the history of life on Earth. Modern biota (both flora and fauna) show a general increase in biodiversity from high to low latitudes in both terrestrial and marine settings that is considered a major signature of life on the planet. However, the pervasive nature of latitudinal biodiversity gradients has been questioned from palaeontological, deep time, perspectives. Fossil data seem to indicate contrasting patterns between greenhouse and icehouse intervals in the Phanerozoic, with some taxonomic groups showing diversity peaks in palaeotemperate (as opposed to palaeotropic) latitudes, with distribution largely influenced by available environment (highlighted within terrestrial vertebrates) during warm intervals.
The proposed project will seek to critically test the link between palaeoclimate and palaeolatitudinal diversity with a particular focus on geological intervals that document the transition from greenhouse to icehouse conditions (e.g., in the early Cenozoic contrast the warm Eocene with the cooler Oligocene) and subsequent rebound following mass extinction events, in a number of co-existing marine taxonomic groups (fish, ostracods and foraminifera), drawing comparisons with latitudinal patterns among terrestrial vertebrates. It will also assess the influence of environmental occurrence (in the marine realm, emphasising onshore/offshore and benthic/planktonic) on patterns of diversity and resilience in a palaeolatitudinal context.
The project focuses on critical evaluation and synthesis of published datasets, e.g., the Paleobiology Database [PaleoDB] and other taxonomic databases, as principle sources of data enhanced by the collection of additional occurrence data from primary literature sources. Work will be conducted at a variety of spatial and temporal scales using sampling standardisation approaches to ensure that recovered patterns are biological rather than an artefact of the geographic distribution of collected fossil localities or the intensity with which those localities have been sampled. Recovered patterns will be compared quantitively through time within and across taxonomic groups, and to spatial and temporal changes in global and regional climate evolution and environmental and sea level change. This will allow the student to accurately characterise the deep time latitudinal gradients and pinpoint if and how these gradients shift in the greenhouse/icehouse transition.
Training and Skills
As part of CENTA program, students will attend 45 days training throughout their PhD, including a 10 day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to the student's projects and themes.
Project-specific training will include quantitative approaches to diversity reconstruction (including use of the PaleoDB), programming skills using R, use of geographical information systems to analyse and model spatial and temporal data. Key synthetic aspects of the project will include hypothesis testing from different subsets of the project data, and construction of diversity information through time to determine palaeolatitudinal distribution patterns. The student will also learn how to evaluate palaeoenvironments from sedimentary and fossil data.
Year 1: Data gathering, including determining the geographical range to be studied and to identify suitable primary sources for the project. Training in the utility of the PaleoDB (data entry, exploration and data extraction).
Year 2: Commence data analysis establish robust qualitative and quantitative methods where appropriate. Integration of distribution database and palaeogeographic maps (using GIS). Presentation of initial results at Palaeontological Association Annual Meeting
Year 3: Data analysis including biogeography methods, correcting for sampling bias and reconstruction of latitudinal gradients through time. Presentation of project results at Geological Society of America.
Ivan Sansom (I.J.Sansom@bham.ac.uk)