November 24, 2020
Open Science Practices in Phytolith Research and Beyond
Open science is becoming an integral part of all scientific research but the extent of these practices in many fields is unknown, including phytolith research. I will present the findings of my recent project concerning the assessment of open science practices in phytolith research. My research assessed data and metadata sharing, and open access, in a sample of journal articles containing primary phytolith data from 16 prominent archaeological and palaeoecological journals (341 articles). It builds on similar studies conducted for archaeological science (Marwick & Pilaar Birch 2018) and macro-botanical remains (Lodwick 2019). I collected data concerning data format, reusability of data, inclusion of phytolith morphotype pictures for identification purposes and a fully described method, use of the International code for phytolith nomenclature (ICPN) and whether the articles were open access. I will suggest steps forward to use as a starting point for discussions in the wider phytolith and academic communities to develop guidelines for greater integration of open science practices and discuss how a move to a more holistic open approach will produce a more sustainable future for our research.
University of Arizona
November 17, 2020
Methane, Monsoons, and Modulation of Millennial-scale Variability
Earth’s orbital geometry exerts a profound influence on climate by regulating changes in incoming solar radiation. Superimposed on orbitally paced climate change, Pleistocene records reveal substantial millennial-scale variability characterized by abrupt changes and rapid swings. However, the extent to which orbital forcing modulates the amplitude and timing of these millennial variations is unclear. Here we isolate the magnitude of millennial-scale variability (MMV) in two well-dated records, both linked to precession cycles (19,000- and 23,000-year periodicity): composite Chinese speleothem δ¹⁸O, commonly interpreted as a proxy for Asian monsoon intensity, and atmospheric methane. At the millennial timescale (1,000–10,000 years), we find a fundamental decoupling wherein precession directly modulates the MMV of methane but not that of speleothem δ¹⁸O, which is shown to be strikingly similar to the MMV of Antarctic ice core δ²H. One explanation is that the MMV of methane responds to changes in midlatitude to high-latitude insolation, whereas speleothem δ¹⁸O is modulated by internal climate feedbacks.
University of Birmingham
November 10, 2020
All fossils are rotten: understanding decay is key to understanding exceptionally preserved fossils
The fossil record is our only ‘window’ into the evolution of animals and plants throughout geological history. Unfortunately, this window is murky, because nature favours obliteration of organic material – predominately through decay – which acts to remove information from the fossil record. Of course, organics do preserve, and these are usually tissues that have a high preservation potential (are more decay-resistant) such as biomineralised tissues (bones, teeth, shells etc.) which explains their dominance in the fossil record. There are, however, processes in certain depositional environments that allow an organism’s soft-tissues to enter the inorganic lithosphere. These soft-tissue fossils are important as they allow more accurate reconstructions of ancient ecosystems and because they retain vital anatomical information which can be used to investigate animal evolution, especially during pivotal periods of Earth’s history, like the Cambrian Explosion. The science of taphonomy seeks to understand the processes that control preservation of organics, from the immediate moments after death and subsequent burial (biostratinomy), mineralisation, diageneses, and geological processes. My talk will introduce experimental taphonomy and will showcase my work trying to understand three tiers of taphonomic bias: 1) preservational potential of different tissue types within an organism, 2) varying preservational potential of related organisms and 3) the impact of paleogeography on soft-tissue preservation.
November 3, 2020
Quantitative pollen-based vegetation reconstructions
Understanding land use and land cover (LULC) change through time is an important aspect when attempting to interpret human-environment interactions through time. Palaeoenvironmental techniques have been crucial in bridging this gap by providing information that has been used to estimate climate change, vegetation change, sea level change etc. through time using a variety of proxies. Producing quantitative land-cover reconstructions has been an aim and a challenge with several methods attempted during the decades. In LandClimII (Land and Climate interactions in Europe during the Holocene project, we use the REVEALS model, which has been tested and validated, in several regions of the world. REVEALS is a Landscape Reconstruction Algorithm model that estimates vegetation abundance/plant cover at the regional scale (100 km x 100 km). The LRA is the most widely tested, validated, and applied pollen-based quantitative reconstruction approach to date.
University of Colorado Boulder
October 27, 2020
Recent advances in using the hydrogen and oxygen isotopes of biomarkers in Arctic lake sediments to reconstruct precipitation isotopes
Global climate models project that over the coming century precipitation patterns will change as temperatures rise. Environmental and social structures are sensitive to regional changes in the hydrologic cycle and more extreme expressions of precipitation (e.g. droughts, flooding) will have far reaching consequences. Predicting local-to-regional scale changes is thus important for helping communities prepare for and navigate a new normal. Geologic records of past climate provide insight into how the climate system responded during periods warmer-than-present. However, precipitation remains a difficult climate variable to reconstruct. The goals of this talk are to provide a broad overview of recent advances in using the hydrogen (H) isotopes of sedimentary plant waxes to reconstruct precipitation isotopes, which relate to moisture pathways and local climate conditions, and highlight where new tools like coupled oxygen (O) and H isotope records or new H isotope proxies show strong promise. In particular, I’ll focus on my work using H isotopes of leaf wax biomarkers to reconstruct precipitation isotopes at multiple sites on Greenland for the last 10,000 years, compare sedimentary wax H isotope data to the oxygen (O) isotopic composition of aquatic insects from the same records, and highlight recent discoveries regarding the strengths and weaknesses of wax biomarkers in this pursuit. Additionally, I’ll introduce ongoing work to relate the H isotopic composition of n-alkyl chains derived from brGDGTs to that of soil and lake water isotopes in Arctic Canada.
October 20, 2020
The Rise of Mammals after the End-Cretaceous Mass Extinction
Living mammals exhibit vast morphological and ecological diversity from the tiny two-gram bumblebee bat capable of powered flight to the fully aquatic deep-diving blue whale, the largest animal known to have ever existed. The foundations of mammal diversity were established in the Mesozoic, but it was not until after the end-Cretaceous mass extinction and the demise of the non-avian dinosaurs that mammals began to increase in body size, diversify into many new species and establish the extant lineages we recognise today. Despite a global presence, fundamental questions regarding the evolutionary relationships and divergence dates of placental mammals remain largely unresolved. This is thought to be, in part, due to our relatively poor knowledge regarding the palaeobiology and phylogeny of the Paleocene mammals, those species that diversified immediately after the extinction, and which are often perceived as ‘archaic’ precursors to the extant lineages.
This talk focuses on some of the broader goals of my on-going research into Paleocene mammal palaeobiology and phylogeny and will discuss the findings of a recent project investigating the locomotor ecology of Paleocene mammals. Results from this study show that Paleocene mammals were far from ‘archaic’ precursors, instead they were products of a post-extinction adaptive radiation that combined a basic placental mammal bauplan with inimitable anatomical specialisations not easily comparable to extant mammals, exemplifying their evolution following a catastrophic mass extinction event.
October 13, 2020
A New Approach to Glossopteris Leaf Taxonomy Embracing Morphometric Analyses
Glossopteris leaves are one of the most common and easily recognised Permian fossils across Gondwana, but they are morphologically conservative and taxonomic approaches to species differentiation have been varied, relying on visual estimations of relatively plastic characteristics such as shape, length etc. Species identification in the past has therefore proven to be subjective, inconsistent and extremely challenging.
To address these taxonomic challenges, we have produced the first morphometric study using Glossopteris leaves from two localities in the Karoo Basin of South Africa: a new site on the Ouberg Pass (Northern Cape Province) and Kwa-Yaya (KwaZulu-Natal Province). The Ouberg Pass lies in the southern Karoo Basin, in a region rich in fossils of terrestrial vertebrates of the Tapinocephalus Assemblage Zone. A detailed biostratigraphic framework, together with multiple ash dates in the immediate area, provided excellent context for this study of a well-preserved, middle Permian parautochthonous flora. The Kwa-Yaya locality, in the late Permian Emakwezini Formation of the Lebombo Basin in the eastern Karoo Basin, has yielded a superbly preserved and diverse, parautochthonous flora. For this study, 43 qualitative leaf features were measured and analysed to identify morphological characteristics that could produce well defined specimen clusters. The morphometric analysis included: leaf length, width, vein angles (proximal, medial, and marginal), mesh areas and width, and leaf area among other features. Fifteen qualitative features were also considered. Our results suggest that the use of the medial portion of the leaf produced the most discrete clusters; and that a combination of features (vein angles, mesh width, mesh area, and leaf area) provided the most reasonable grounds for morphologically defined taxonomic discrimination of species. This work has been used for the development of a standardized leaf characterization template that we hope will facilitate more reliable and consistent typification of glossopterid leaves in South Africa and other regions of Gondwana.
October 6, 2020
Burning Questions: The role of fire ecology in the Neogene expansion of C4 grasslands
Fire is crucial to maintaining modern subtropical grasslands, yet our empirical support for the origins and evolution of this association is limited by a dearth of coeval records of both grass and fire proxies in pre-Quaternary sediments. Polycyclic aromatic hydrocarbons (PAHs) are a suite of molecules that can derive both from the burning of terrestrial vegetation and from thermal maturation of organic matter. I developed an approach to quantitatively source these molecules to enable reconstructions of Neogene fire occurrence. Here, I test hypothesis that fire-feedbacks facilitated the rise of C4 vegetation in the Mio-Pliocene using Pyrogenic PAH abundance patterns alongside records of δ13C of leaf waxes on two continents. Fire-derived PAH relative abundances jumped an order of magnitude in association with a rise in grass inputs recorded at the landscape (Pakistan) and continental scale (Bengal Fan) in South Asia, but not in Australia. These results support fire disturbance as a critical mechanism of terrestrial biome transitions, but emphasize the need to reconstruct fire explicitly alongside other climate and ecological variables, as fire-feedbacks can differ drastically between continents.
Universidad Peruana Cayetano Heredia
September 29, 2020
(Paleo)Ecology of benthic foraminifera in anoxic sediments: the reconstruction of the OMZ off Peru in the last millenium
Benthic foraminifera are testate protists that thrive in several extreme environments, such as sediments of oxygen minimum zones (OMZ). The natural variability of OMZs is shaped by climate and ocean dynamics, but anthropogenic forcing increases the oxygen deficiency near the coast. In Peru, the OMZ is shallow and intense and has suffered changes in the past. How is it responding in recent centuries? Is it expanding with global warming? Here I show how ‘forams’ reflect the changing environmental conditions of OMZ off Peru in the last millenium through their ecological features.
Gabi Serrato Marks
September 22, 2020
New speleothem-derived insights into northern Mexican paleoclimate during the first millennium of the Common Era
There were major population centers in northern Mexico, including the city of Teotihuacan, that experienced dramatic shifts during the first millennium of the Common Era (CE), but we lack precisely dated and high resolution paleoclimate records to investigate the climate events under which these civilizations survived or collapsed. I will present a precisely dated speleothem from San Luis Potosí, Mexico (289 ± 13 to 976 ± 29 CE) as a new record of hydroclimatic change. We used stable isotopes and trace metal to calcium ratios to identify several shifts toward drier conditions, indicating the presence of multidecadal droughts.
September 15, 2020
Intermixed Messages: geochemical and paleontological records of the end-Devonian Hangenberg Crisis in the Appalachian Basin, USA
The end-Devonian Hangenberg Crisis constituted one of the greatest ecological and environmental perturbations of the Paleozoic Era. While this biocrisis is considered a global event, its cause and overarching effects remain uncertain, especially within the Appalachian Basin of the United States. We integrate geochemical and paleontological records to characterize the onset and paleoenvironmental transitions associated with the Hangenberg Crisis within the Cleveland Shale member of the Ohio Shale. Organic geochemical proxies such as lipid biomarker analysis and stable isotopes allow us to probe the dynamics of the microbial communities that drove Devonian biogeochemical cycles before, during, and after the extinction event. Results indicate that much of the end-Devonian water column was euxinic (anoxic with free hydrogen sulfide). Regardless of this ubiquitous euxinic signal, there is an overprinted record of bioturbation, or the traces of past burrowing organisms, which suggests that the seafloor was not continuously devoid of life. Despite highly variable water column and sedimentary redox conditions, as well as the extinction known to be occurring in macrofaunal clades, lipid biomarker evidence shows that there is little to no change in the microbial communities that drive the base of the food chain at any point during this biotic crisis.
Emanuela di Martino
University of Oslo
September 8, 2020
A walk through the fascinating world of BRYOZOANS: what can they tell us about the past?
In my research, I use fossil bryozoans as a model system to answer paleobiological and macroevolutionary questions.
Bryozoans are a phylum of invertebrate, aquatic, colonial animals which made their first appearance in the Ordovician and are still successfully colonizing the oceans today.
Although bryozoans were the subject of Charles Darwin’s first scientific paper, at that time they were classified as zoophytes because of their puzzling attributes seemingly somewhere between animals and plants. Even today they are very little known among non-specialists.
Nonetheless, calcified bryozoans provide an optimal model system in studies of biodiversity, paleoecology and evolution for several reasons. They are major components of the marine benthos in both modern and ancient oceans. They are distributed globally in a wide range of habitats and at all depths. They have diagenetically resistant and typically well-preserved skeletons. Their skeletal complexity provides a wealth of characters for a rigorous species-level taxonomy. Furthermore, their skeletal morphology directly reflects life history variation and ecological function, a rarity in the fossil record.
In this talk, I will show examples of what bryozoans can tell us about the past. These include studies from my previous and current research projects in:
i) Biodiversity: I used extensive paleontological collections of Caribbean and Indonesian bryozoans to address the timing of the divergence in species richness between the two regions and to evaluate the relative contributions of differential rates of origination and extinction to the diversity patterns we observe today.
ii) Paleoecology: As the majority of bryozoans live as encrusters of hard substrates such as rocks and shells, substrate availability is a prime factor controlling their distribution, often leading to competition for space among colonies or other organisms. These competitive interactions entail skeletal overgrowths which can be preserved in the fossil record, offering one of the few systems in which to study directly competition and its consequences in the geological past.
iii) Macroevolution: Capitalizing on the polymorphic nature of bryozoans and the separation between feeding and reproductive individuals within colonies, we can tackle the outstanding problem of using the fossil record to estimate trait-fitness associations for phenotypic traits, and ask if such associations are consistent with macroevolutionary patterns of the same phenotypes.
University of Kansas
September 1, 2020
Out of the dark: The mysterious origins and rapid diversification of bats
Bats are the second most species-rich group of living mammals, with over 1400 species currently known. The earliest fossil bats date to ~55 Ma, and new species of Eocene bats continue to be named from localities around the world. Despite their living and fossil diversity, the evolutionary origins and biogeographic history of bats remain effectively unknown. Fossil bats appear nearly simultaneously on continents as distant as Australia and Europe, and no transitional bat fossils are currently recognized. Because the fossil record of bats is acknowledged to be poor compared to that of other mammals, creative methods must be employed to understand the origins and biogeography of the order. I present ongoing work describing some of the earliest known bat fossils, with implications for understanding the paleoecology and region of origin of Eocene bats. I also discuss challenges and approaches for understanding the potential outgroups of bats in the Paleocene.