Angiosperms (flowering plants) are an extremely diverse group of terrestrial plants composed of an estimated 260,000 species. They are characterised by high morphological diversity, with an array of life forms that includes herbs, epiphytes, bulbs, aquatic plants, shrubs and trees. Angiosperms have unique anatomical features, enabling them to be powerful agents of climatic change. In particular, angiosperms have evolved physiological adaptations that provide them with uniquely high transpiration capacities. This means that they contribute significantly to the amount of precipitation that falls in the tropics, increasing the area that can be vegetated by rainforests. The evolution of angiosperms therefore represents a fundamental event in the evolution of the Earth, and the regulation of its climate system.
Despite the evolutionary and climatic importance of angiosperms, our understanding of their long-term patterns of early evolution remains patchy. Existing data from North America indicate that angiosperms radiated during the Cretaceous period (~150–65 million years ago), but that their taxonomic and morphological evolution was decoupled (Lupia 1999). In particular, the earliest phases of angiosperm evolution were characterised by the rapid and explosive addition of novel and highly disparate morphologies as angiosperms spread over the Earth.
However, this macroevolutionary pattern has only been reported in North America at the stage level using published literature. Consequently, it is currently unclear whether the early and rapid evolution of novel and highly disparate morphologies is characteristic of angiosperm evolution in general, or a regional phenomenon. Additionally, the coarse time-scales of existing macroevolutionary analyses (Lupia 1999) mean that we do not know whether these plants speciated gradually, or their evolution was characterised by a punctuated pattern with periods of rapid speciation followed by long-term stasis (Benton and Pearson 2001).
This PhD project will address these fundamental evolutionary issues by using fossil pollen from existing rock samples taken from the Alaskan Arctic Slope (Herman et al. 2016). These fossiliferous deposits span the Albian–Maastrichtian, a critical phase of angiosperm evolution, and represent an opportunity to investigate an extinct near-polar ecosystem in a warm world. This project will also use samples from the early Cenomanian (~98–95 Ma) Warder Formation, New Zealand, to generate a detailed biogeographic comparison between the southern and northern hemispheres. This project has aims to:
(1) Make a quantitative assessment of the taxonomic diversity and morphological disparity of angiosperm pollen from the Albian–Maastrichtian of the Alaskan Arctic Slope.
(2) Reconstruct the mode (gradual or punctuated) of angiosperm evolution in this region.
(3) Generate a biogeographic comparison of the diversity and disparity of the Cenomanian of the
Alaskan Arctic Slope and the Warder Formation, New Zealand.
Existing rock samples (150 from Alaska and 40 from New Zealand) will be macerated in the laboratory using standard palynological processing techniques to release fossil angiosperm pollen grains. The diversity and disparity of these pollen grains will be assessed by scoring individual specimens for discrete morphological characters and measuring the nature of morphospace occupation through time using the methods of Mander (2016). The mode of angiosperm evolution will be assessed by making morphometric measurements of key taxa. These measurements will be plotted against time to test for gradual versus punctuated modes of evolution. Biogeographic comparison between the Cenomanian of Alaska and New Zealand will involve reconstructing the diversity and composition of the vegetation in these two regions using fossil pollen.
Training and Skills
This project will provide specific training in:
(1) Palynological techniques to extract fossil pollen from rock samples.
(2) The description of plant morphology using morphometric techniques.
(3) The use of high-resolution optical and electron microscopy.
(4) Macroevolutionary analytical techniques to examine the morphological and taxonomic diversification of major clades.
NERC CENTA students are required to complete 45 days training throughout their PhD including a 10 day work 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 CENTA research themes
Year 1: Macerate rock samples in laboratory in order to release fossil angiosperm pollen grains. Generate a morphospace for early angiosperm pollen. Attend the Palaeontological Association Annual Meeting.
Year 2: Complete morphospace analyses of Alaskan and New Zealand angiosperm pollen. Make morphometric measurements of key angiosperm pollen grains to reconstruct the mode of flowering plant evolution. Compare results from the two sites. Preparation of manuscript. Present at the Palaeontological Association Annual Meeting. Complete work placement.
Year 3: Complete interpretation. Prepare two further manuscripts and write up thesis. Present results at the Geological Society of America annual meeting.
Partners and collaboration (including CASE)
This project will benefit from collaboration with Dr. Liz Kennedy (GNS Science, New Zealand)
Students should have a strong background in Earth science or biology and enthusiasm for plants. Experience of undertaking independent fieldwork and research working in a laboratory is desirable. The student will join a well-established team researching ecology, evolution and palaeoenvironmental change at the Open University.
Please contact Luke.Mander@open.ac.ukfor further information.
Applications should include:
- a cover letter outlining why the project is of interest and how their skills match those required,
- an academic CV containing contact details of three academic references
- a CENTA application form, downloadable from: http://www.centa.org.uk/media/1202/centa-studentship-application-form.docx
- and an Open University application form, downloadable from: http://www.open.ac.uk/students/research/sites/www.open.ac.uk.students.research/files/documents/Application%20form.docx
Applications should be sent to
by 5 pm on Monday 22nd January 2018