2008 Annual General Meeting
Microfossils and Extinction
19th November, 2008, 1.15pm, J. Z. Young Lecture Theatre, University College London
19th November, 2008, 1.15pm, J. Z. Young Lecture Theatre, University College London
1:30-2:00 Society business
2:00-5:30 Scientific programme
Dr David Bass, The Natural History Museum , London
Evolutionary and ecological complexity of unicellular eukaryotes
Dr Philip C. J. Donoghue, Department of Earth Sciences, University of Bristol
Embryos and ancestors: embryology at the dawn of animal evolution
Dr Charles H. Wellman, Department of Animal and Plant Sciences, University of Sheffield
The palynological record of the origin and adaptive radiation of land plants
3:30-4:00 Coffe break in South Cloisters
Professor Koenraad Martens, Museum of Natural Sciences, Brussels
Asexual ostracods in space and time
Professor Paul Pearson, School of Earth and Ocean Sciences, Cardiff University
Macro- and microevolution in Cenozoic planktonic foraminifera
Dr David Lazarus, Humbold-Museum of Natural History, Berlin
Radiolarian evolution: patterns, current understanding and prospects for future research
5:30-6:00 Awards ceremony
6:00-7:30 Wine reception in South Cloisters
Evolutionary and ecological complexity of unicellular eukaryotes
Dr David Bass
Zoology Department, The Natural History Museum , London
Recently, developments in phylogenetic analyses have enabled significant advances towards resolving evolutionary relationships among protozoan lineages, which themselves represent a large proportion of the evolutionary history of eukaryotes including their earliest branches. These developments include methods analysing the evolution of gene sequences among taxa, the distribution of molecular characters such as gene fusions and insertions, and the simultaneous analysis of multiple genes culminating in the current emergence of large-scale ‘phylogenomic’ studies. Such approaches are simplifying the classification of eukaryotes into a small number of diverse ‘supergroups’, e.g. unikonts (=opisthokonts plus Amoebozoa), excavates, plants, haptophytes plus cryptophytes, and the SAR group (alveolates, stramenopiles, and Rhizaria). However, this process is very much in flux and the supergroup view of eukaryote life varies among research groups as new data appear and different analytical approaches are taken. I will discuss the evolutionary diversity and phylogeny of Rhizaria, one of the least well known of the supergroups. Rhizaria is very lineage-rich and morphologically/ecologically diverse, comprising the phyla Cercozoa, Radiozoa, and Foraminifera. However, recent results are questioning this trinity and may lead to the creation of new taxa in the near future. I will then focus on the relatively new phylum Cercozoa, its internal relationships and those with other Rhizaria, and will outline some of the studies currently underway on members of this highly diverse phylum.
Embryos and ancestors: embryology at the dawn of animal evolution
Dr Philip C. J. Donoghue
Department of Earth Sciences, University of Bristol
Evolutionary change is effected through changes in embryology. Fossilised embryos, discovered in rocks laid down contemporaneously with the emergence of animal phyla, provide a unique snapshot into the embryology of early animals. These microscopic fossils are beginning to contribute to classical debates in the evolutionary embryology, such as the primacy of cleavage modes and the strategies of life history adopted by the earliest animals in comparison to their living relatives.
The palynological record of the origin and adaptive radiation of land plants
Charles H. Wellman
Department of Animal & Plant Sciences, University of Sheffield , Alfred Denny Building, Western Bank, Sheffield S10 2TN , UK
The fossil record suggests that plants invaded the land at least 30 million years before the first vascular plants appeared in the Early Silurian. The earliest vegetation consisted of stem group embryophytes believed to have been at a bryophytic grade of organization. These plants were widespread and probably generalists that tolerated a wide range of environments. The emergence of polysporangiophytes (vascular plants and their immediate predecessors) probably coincided with the shift from gametophyte to sporophyte dominance. This unleashed evolutionary potential in that the sporophyte is diploid and ultimately evolved lignified tracheids. In particular the evolution of a rigid and efficient conducting system allowed plants to increase in height and begin to explore whole new vistas of morphospace. This sparked an adaptive radiation of vascular plants seen in both the plant megafossil and the dispersed spore fossil records. The former is notoriously incomplete and biased, arguably relying on a few temporally/spatially scattered assemblages. On the other hand the dispersed spore fossil record is more complete, and exhibits clear patterns of diversification in terms of changing diversity, disparity and palaeophytogeography. These patterns been quantitatively analysed based on taxon counts, development of a “spore disparity index”, and palaeogeographic consideration of both of these measures. Preliminary results suggest that biogeographic spread of vascular plants was complex, involving different lineages on different continents. Interestingly, on each of the continents the structure of the adaptive radiation appears to have been similar with comparable patterns of diversity and disparity increase.
Asexual ostracods in space and time
Koenraad Martens
Ostracods are small, bivalved crustaceans that abound in a variety of limni and (semi-) terrestrial enviornments. They are excellent model organisms for evolutionary studies, as their excellent fossil record allows the study of evolutionary processes in real-time frames. In addition, they have a range of reproductive modes, so that they can be used to study the so-called „paradox of sex“. There are fully sexcual ostracods, a large number of species with mixed reproduction (in which often also geographical parthenogenesis occurs) and putative ancient asexuals. Representatives of the latter two groups are studied with a variety of methods, including palaeontology, molecular biology, phylogeny and ecology.
Macro- and microevolution in Cenozoic planktonic foraminifera
Paul N Pearson
School of Earth and Ocean Sciences, Cardiff University
Decades of systematic ocean drilling targeting sites with relatively continuous sedimentation has resulted in an excellent fossil record of planktonic foraminifera. After the end-Cretaceous mass extinction, the group underwent a major adaptive radiation followed by a long history of fluctuating diversity that continues up to the present. Peak diversity has always been in tropical and subtropical open-ocean settings, although some groups have specialized in cold and/or high productivity environments. Geochemical studies show how some clades have adopted symbiotic associations while others have adapted to different depth habitats in the open ocean. Ongoing developments in systematic taxonomy, phylogeny and biostratigraphy are revealing details of the macroevolutionary pattern more clearly than ever before including the influence of climate perturbations such as at the Eocene/Oligocene boundary. Many evolutionary lineages have been studied in detail over the years, revealing a predominance of gradual evolution in test size and shape, including some striking instances of morphological innovation. However genetic studies have revealed a diversity of cryptic genotypes suggesting that a degree of hidden biodiversity underlies the traditional morphospecies. Curiously, there is a preponderance of sudden, apparently inexplicable extinctions in the record, whereas the major climatic swings of the Pleistocene have not had a lasting effect. Mysterious apparent periodicities in speciation and extinction rates remain unexplained. Significant puzzles still exist, therefore, and followingDarwin
Decades of systematic ocean drilling targeting sites with relatively continuous sedimentation has resulted in an excellent fossil record of planktonic foraminifera. After the end-Cretaceous mass extinction, the group underwent a major adaptive radiation followed by a long history of fluctuating diversity that continues up to the present. Peak diversity has always been in tropical and subtropical open-ocean settings, although some groups have specialized in cold and/or high productivity environments. Geochemical studies show how some clades have adopted symbiotic associations while others have adapted to different depth habitats in the open ocean. Ongoing developments in systematic taxonomy, phylogeny and biostratigraphy are revealing details of the macroevolutionary pattern more clearly than ever before including the influence of climate perturbations such as at the Eocene/Oligocene boundary. Many evolutionary lineages have been studied in detail over the years, revealing a predominance of gradual evolution in test size and shape, including some striking instances of morphological innovation. However genetic studies have revealed a diversity of cryptic genotypes suggesting that a degree of hidden biodiversity underlies the traditional morphospecies. Curiously, there is a preponderance of sudden, apparently inexplicable extinctions in the record, whereas the major climatic swings of the Pleistocene have not had a lasting effect. Mysterious apparent periodicities in speciation and extinction rates remain unexplained. Significant puzzles still exist, therefore, and following
Radiolarian evolution: patterns, current understanding and prospects for future research
Dr David Lazarus
Museum für Naturkunde, Invalidenstrasse 43, 10115 Berlin
Patterns of radiolarian change from their origins in the early Paleozoic to the Recent pose a rich variety of questions for evolutionary biology. These include fundamental questions on the meaning of diversity of form (much higher in radiolarians than in the ecologically similar planktonic foraminifera), concepts of evolutionary progress (for which there is little evidence in post-Paleozoic radiolaria, despite 250 my of evolutionary change), and mechanisms of microevolutionary change in plankton (very diverse, based on many studies of radiolarian speciation, phyletic change and possibly hybridization). Radiolarians also show aspects of evolution not seen in calcareous plankton groups, including distinctly different patterns of evolutionary response to mass extinctions; long-term co-evolutionary change (with diatoms) and significantly more complex patterns of latitudinal and depth diversification. Recent improvements in the availability of well dated materials (IODP drilling; global MRC collections), databases (Neptune, PBDB, radiolaria.org), imaging and morphometric techniques, as well as improved knowledge of radiolarian genetics and water column ecology provide a wealth of new opportunities to advance our understanding of radiolarian evolution, and more generally, our understanding of evolution in the planktonic realm.
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