My research investigates the role of ecological processes on evolution through deep-time, from the first animal communities of the Ediacaran, to the present. The first animal communities are found in the Ediacaran time period, 580 million years ago, which consisted of sessile benthic organisms that lived in the deep-sea. Therefore, to understand how macro-ecology has changed through deep-time, I study a wide range of different benthic communities from the fossil record and in the modern Antarctic and deep-sea. To collect fossil data in the field, I use novel field-based laser-scanning techniques from aerospace to digitally capture entire rock surfaces. My work on modern systems uses data collected using AOV and ROVs to create 3D digital models. Through the application of statistical and mathematical ecology to the fossil and modern benthic communities, I reconstruct how species interact with each other and their environment, and what the driving factors behind these interactions are. These results then feed into theoretical models to explore how these relationships influence macro-evolutionary patterns over the last 580 million years. Supervisors: Nick Butterfield and Anje Neutel
<p>Oxygenation during the Cambrian Radiation progressed via a series of short-lived... more <p>Oxygenation during the Cambrian Radiation progressed via a series of short-lived pulses. However, the metazoan biotic response to this episodic oxygenation (and potentially productivity changes) has not been quantified, nor have the causal evolutionary processes been constrained. Here we present analyses of the dynamics of early Cambrian metazoan body size changes, habitat distribution, and ecological complexity on the Siberian Platform (525–510 Ma).</p> <p>First, we quantify high-resolution changes in species body size in archaeocyath sponges, hyolith lophophorates, and helcionelloid molluscs, and brachiopods. Archaeocyath, hyoliths, and helcionelloids, show dynamic and synchronous trends over million-year timescales, with peaks in body size during the latest Tommotian/early Atdabanian (~521–519 Ma) and late Atdabanian/early Botoman (~519–516.5 Ma), and notably small body sizes in the middle Atdabanian and after the Sinsk anoxic extinction event, starting ca. 513 Ma. These intervals of body size changes are also mirrored in individual species and correlate positively with increased rates of origination and broadly with total species diversity. Calcitic brachiopods (rhynchonelliformeans), however, show a general increase in body size following the increase in species diversity through this interval; phosphatic brachiopods (linguliformeans) show a body size decrease that negatively correlates with diversity. Both brachiopod groups show a rapid recovery at the Sinsk Event. The synchronous changes in these metrics in archaeocyaths, hyoliths and helcionelloids suggest the operation of external drivers through the early Cambrian, coincident with two oxic or productivity pulses. But the trends shown by brachiopods suggests a differing physiological response. Together, these dynamics created both the distinct evolutionary record of metazoan groups during the Cambrian Explosion and determined the nature of its termination.</p> <p>Second, during the oxic pulse at ~521–519 Ma, we quantify the expansion of archaeocyath sponge reef habitat coupled to an increase in reef size and metacommunity complexity, from individual within-community reactions to their local environment, to ecologically complex synchronous community-wide response, accompanied by an increase in rates of origination. Subsequently, reef and archaeocyath body size are reduced in association with increased rates of extinction due to inferred expanded marine anoxia (~519–516.5 Ma). The later oxic pulse at ~515 Ma shows further reef habitat expansion, increased archaeocyath body size and diversity, but weaker community-wide environmental responses.</p> <p>These metrics confirm that oxygenation events created temporary pulses of evolutionary diversification and enhanced ecosystem complexity, potentially via the expansion of habitable space, and increased archaeocyath individual and reef longevity in turn leading to niche differentiation. Most notably, we show that progression towards increasing biodiversity and ecosystem complexity was episodic and discontinuous, rather than linear, during the Cambrian Radiation.</p> <p> </p>
The timing of the first appearance of animals is of crucial importance for understanding the evol... more The timing of the first appearance of animals is of crucial importance for understanding the evolution of life on Earth. Although the fossil record places the earliest metazoans at 572–602 Ma, molecular clock studies suggest a far earlier origination, as far back as ~850 Ma. The difference in these dates would place the rise of animal life into a time period punctuated by multiple colossal, potentially global, glacial events. Although the two schools of thought debate the limitations of each other's methods, little time has been dedicated to how animal life might have survived if it did arise before or during these global glacial periods. The history of recent polar biota shows that organisms have found ways of persisting on and around the ice of the Antarctic continent throughout the Last Glacial Maximum (33–14 Ka), with some endemic species present before the breakup of Gondwana (180–23 Ma). Here we discuss the survival strategies and habitats of modern polar marine organisms ...
Los ejemplares de Dickinsonia de los Urales Centrales se caracterizan por una clara simetría bila... more Los ejemplares de Dickinsonia de los Urales Centrales se caracterizan por una clara simetría bilateral. Tomando en cuenta las observaciones de especímenes australianos, consideramos que la llamada’simetría de reflexión por deslizamiento’ en estos fósiles es un fenómeno tafonómico. El gráfico de distribución de frecuencias de tamaño muestra el predominio de individuos juveniles en la población estudiada de Dickinsonia de los Urales Centrales. Asumiendo que la edad de un individuo se manifiesta por su tamaño, existe un predominio significativo de individuos juveniles en la población. Se pueden prever tres escenarios posibles: (1) la población tiene un gran número de individuos juveniles como resultado de la alta tasa de supervivencia en la zona intermareal; (2) la población está dominada por formas juveniles porque está enterrada inmediatamente después de la eclosión; (3) suponiendo que Dickinsonia fuera un organismo móvil activo, la abundancia de individuos juveniles podría explicars...
The carotid bifurcation has been a region of particular interest due to its predilection for clin... more The carotid bifurcation has been a region of particular interest due to its predilection for clinically significant atherosclerosis. It has been shown that the vessel geometry is a major determinant of the local haemodynamic properties which are believed to be associated with the location of atherosclerotic lesions. Current knowledge of the geometry of the carotid bifurcation is insufficient and restricted to basic geometric parameters. To provide some means of quantifying the degree of complexity of the 3D shape of the bifurcation, we made an initial attempt by evaluating the non-planarity of an arterial bifurcation based upon the singular value decomposition theorem. In this paper we present our results obtained on the right carotid bifurcations of six normal subjects, each of whom was scanned twice using the 2D time-of-flight MR sequence. The acquired 2D cross sectional images were processed by using our in-house software which comprises 2D segmentation, 3D reconstruction and smo...
Oxygenation during the Cambrian Radiation progressed via a series of short-lived pulses. However,... more Oxygenation during the Cambrian Radiation progressed via a series of short-lived pulses. However, the metazoan biotic response to this episodic oxygenation has not been quantified, nor have the causal evolutionary processes been constrained. Here we present ecological analyses of Cambrian archaeocyath sponge reef communities on the Siberian Platform (525–514 Ma). During the oxic pulse at ~521–519 Ma, we quantify reef habitat expansion coupled to an increase in reef size and metacommunity complexity, from individual within-community reactions to their local environment, to ecologically complex synchronous community-wide response, accompanied by an increase in rates of origination. Subsequently, reef and archaeocyath body size are reduced in association with increased rates of extinction due to inferred expanded marine anoxia (~519–516.5 Ma). A later oxic pulse at ~515 Ma shows further reef habitat expansion, increased archaeocyath body size and diversity, but weaker community-wide en...
The broad-scale environment plays a substantial role in shaping modern marine ecosystems, but the... more The broad-scale environment plays a substantial role in shaping modern marine ecosystems, but the degree to which palaeocommunities were influenced by their environment is unclear. To investigate how broad-scale environment influenced the community ecology of early animal ecosystems we employed spatial point process analyses to examine the community structure of seven bedding-plane assemblages of late Ediacaran age (558–550 Ma), drawn from a range of environmental settings and global localities. The studied palaeocommunities exhibit marked differences in the response of their component taxa to sub-metre-scale habitat heterogeneities on the seafloor. Shallow-marine palaeocommunities were heavily influenced by local habitat heterogeneities, in contrast to their deep-water counterparts. Lower species richness in deep-water Ediacaran assemblages compared to shallow-water counterparts across the studied time-interval could have been driven by this environmental patchiness, because habita...
Trace fossils record foraging behaviors, the search for resources in patchy environments, of anim... more Trace fossils record foraging behaviors, the search for resources in patchy environments, of animals in the rock record. Quantification of the strength, density, and nature of foraging behaviors enables the investigation of how these may have changed through time. Here, we present a novel approach to explore such patterns using spatial point process analyses to quantify the scale and strength of ichnofossil spatial distributions on horizontal bedding planes. To demonstrate the utility of this approach, we use two samples from the terminal Ediacaran Shibantan Member in South China (between 551 and 543 Ma) and the early Cambrian Nagaur Sandstone in northwestern India (between 539 and 509 Ma). We find that ichnotaxa on both surfaces exhibited significant nonhomogeneous lateral patterns, with distinct levels of heterogeneity exhibited by different types of trace fossils. In the Shibantan, two ichnotaxa show evidence for mutual positive aggregation over a shared resource, suggesting the ...
Supplementary file 2: Base data, plotted data (graphical and maps), and analysis data. Plotted da... more Supplementary file 2: Base data, plotted data (graphical and maps), and analysis data. Plotted data and analysis data are derived from the base data, using formulae in Excel. These data and corresponding Excel formulae are presented in the following worksheets.
Pseudoplanktonic crinoid raft colonies are an enigma of the Jurassic. These raft colonies are tho... more Pseudoplanktonic crinoid raft colonies are an enigma of the Jurassic. These raft colonies are thought to have developed as floating filter-feeding communities due to an exceptionally rich oceanic niche, high in the water column enabling them to reach large densities on these log rafts. However, this pseudoplanktonic hypothesis has not been quantitatively tested, and there remains some doubt that this mode of life was possible. The ecological structure of the crinoid colony is resolved using spatial point process analyses and the duration estimates of the floating system until sinking using moisture diffusion models. Using spatial analysis, we found that the crinoids would have trailed preferentially positioned at the back of the floating log in the regions of least resistance, consistent with a floating, not benthic ecology. Additionally, we found using a series of moisture diffusion models at different log densities and sizes that ecosystem collapse did not take place solely due to...
Floating duration (in months) until sinking for small colonies [Göttingen (S1) and Stuttgart 1 (S... more Floating duration (in months) until sinking for small colonies [Göttingen (S1) and Stuttgart 1 (S2) – 40 cm long Diameter 5–6 cm (Community Removed); see Figure 3a] as a function of the dry density (g/cm3) of the material relative to water and its initial moisture content (%). In green wood, diffusion of moisture occurs longitudinally and radially (with a tangential component) for water vapour, liquid water bound to cell walls, and liquid water running free through vessels and tracheids . Initial moisture content reflects the humidity of the surrounding atmosphere (relative humidity) as well as its temperature, and moisture content constrains the diffusion coefficients. In green wood, moisture content can vary between sapwood (>100% where sap flows) and heartwood (~40% closer to the pith) but the model assumes an average moisture content throughout the log. The log will sink as soon as the system {wood log + water} is denser than water. For example (red dotted lines), a log with ...
Floating duration (in months) until critical mass for small colonies [Göttingen (S1) and Stuttgar... more Floating duration (in months) until critical mass for small colonies [Göttingen (S1) and Stuttgart 1 (S2) – 40 cm long Diameter 5–6 cm (Community Included); see Figure 3b] as a function of the dry density (g/cm3) of the material relative to water and its initial moisture content (%). In addition to the soaking process, we have loaded the log with a community of crinoids with an arbitrary individual growth rate extrapolated from extant species of Neocrinus decorus, Endoxocrinus parae and Cenocrinus asterius within [0.6–17.0 cm/yr] (Messing et al. 2007). Monthly growth rates were converted into mass increments using the specific gravity of calcite at 2.7g/cm3. The log will sink as soon as the system {wood log+water+crinoids} is denser than water. In this case, the log sinks at the end of the first monthly increment of growth.
Fig. S1: Locality map. Fig S2: Stratigraphic logs through the Russian sections. Fig S3: High reso... more Fig. S1: Locality map. Fig S2: Stratigraphic logs through the Russian sections. Fig S3: High resolution digitized map of KS surface. Fig S4: : Analyses of the size-distribution of <i>Funisia</i> populations
Floating duration (in months) until critical mass for medium colonies [Holzmaden (G1) and Stuttga... more Floating duration (in months) until critical mass for medium colonies [Holzmaden (G1) and Stuttgart 2 (G2) – 12 m long Diameter 25–28 cm (Community Removed); see Figure 3e] as a function of the dry density (g/cm3) of the material relative to water and its initial moisture content (%). For example, at fiber saturation (30% moisture content), a material of dry density of 0.4 g/cm3 would take approximately 800 months or 66 years (red dotted lines).
Pseudoplanktonic crinoid raft colonies are an enigma of the Jurassic. These raft colonies are tho... more Pseudoplanktonic crinoid raft colonies are an enigma of the Jurassic. These raft colonies are thought to have developed as floating filter-feeding communities due to an exceptionally rich oceanic niche, high in the water column enabling them to reach large densities on these log rafts. However, this pseudoplanktonic hypothesis has not been quantitatively tested, and there remains some doubt that this mode of life was possible. The ecological structure of the crinoid colony is resolved using spatial point process analyses and the duration estimates of the floating system until sinking using moisture diffusion models. Using spatial analysis, we found that the crinoids would have trailed preferentially positioned at the back of the floating log in the regions of least resistance, consistent with a floating, not benthic ecology. Additionally, we found using a series of moisture diffusion models at different log densities and sizes that ecosystem collapse did not take place solely due to...
Evidence for cysts and for ability for cell to change shape, from selected fossil assemblages spa... more Evidence for cysts and for ability for cell to change shape, from selected fossil assemblages spanning late Paleoproterozoic through Tonian time. Age constraints from [1] or as cited in references.
Robust time-series of direct observations of jellyfish abundance are not available for many ecosy... more Robust time-series of direct observations of jellyfish abundance are not available for many ecosystems, leaving it difficult to determine changes in jellyfish abundance, the possible causes (e.g. climate change) or the consequences (e.g. trophic cascades). We sought an indirect ecological route to reconstruct jellyfish abundance in the Irish Sea: since zooplankton are jellyfish prey, historic variability in zooplankton communities may provide proxies for jellyfish abundance. We determined the Bayesian ecological network of jellyfish–zooplankton dependencies using jellyfish- and zooplankton-abundance data obtained using nets during a 2-week cruise to the Irish Sea in 2008. This network revealed that Aurelia aurita abundance was dependent on zooplankton groups Warm Temperate and Temperate Oceanic as defined by previous zooplankton ecology work. We then determined historic zooplankton networks across the Irish Sea from abundance data from Continuous Plankton Recorder surveys conducted ...
Antarctic sea-floor communities are unique, and more closely resemble those of the Palaeozoic tha... more Antarctic sea-floor communities are unique, and more closely resemble those of the Palaeozoic than equivalent contemporary habitats. However, comparatively little is known about the processes that structure these communities or how they might respond to anthropogenic change. In order to investigate likely consequences of a decline or removal of key taxa on community dynamics we use Bayesian network inference to reconstruct ecological networks and infer changes of taxon removal. Here we show that sponges have the greatest influence on the dynamics of the Antarctic benthos. When we removed sponges from the network, the abundances of all major taxa reduced by a mean of 42%, significantly more than changes of substrate. To our knowledge, this study is the first to demonstrate the cascade effects of removing key ecosystem structuring organisms from statistical analyses of Antarctica data and demonstrates the importance of considering the community dynamics when planning ecosystem managem...
&lt;p&gt;Oxygenation during the Cambrian Radiation progressed via a series of short-lived... more &lt;p&gt;Oxygenation during the Cambrian Radiation progressed via a series of short-lived pulses. However, the metazoan biotic response to this episodic oxygenation (and potentially productivity changes) has not been quantified, nor have the causal evolutionary processes been constrained. Here we present analyses of the dynamics of early Cambrian metazoan body size changes, habitat distribution, and ecological complexity on the Siberian Platform (525&amp;#8211;510 Ma).&lt;/p&gt; &lt;p&gt;First, we quantify high-resolution changes in species body size in archaeocyath sponges, hyolith lophophorates, and helcionelloid molluscs, and brachiopods. Archaeocyath, hyoliths, and helcionelloids, show dynamic and synchronous trends over million-year timescales, with peaks in body size during the latest Tommotian/early Atdabanian (~521&amp;#8211;519 Ma) and late Atdabanian/early Botoman (~519&amp;#8211;516.5 Ma), and notably small body sizes in the middle Atdabanian and after the Sinsk anoxic extinction event, starting ca. 513 Ma. These intervals of body size changes are also mirrored in individual species and correlate positively with increased rates of origination and broadly with total species diversity. Calcitic brachiopods (rhynchonelliformeans), however, show a general increase in body size following the increase in species diversity through this interval; phosphatic brachiopods (linguliformeans) show a body size decrease that negatively correlates with diversity. Both brachiopod groups show a rapid recovery at the Sinsk Event. The synchronous changes in these metrics in archaeocyaths, hyoliths and helcionelloids suggest the operation of external drivers through the early Cambrian, coincident with two oxic or productivity pulses. But the trends shown by brachiopods suggests a differing physiological response. Together, these dynamics created both the distinct evolutionary record of metazoan groups during the Cambrian Explosion and determined the nature of its termination.&lt;/p&gt; &lt;p&gt;Second, during the oxic pulse at ~521&amp;#8211;519 Ma, we quantify the expansion of archaeocyath sponge reef habitat coupled to an increase in reef size and metacommunity complexity, from individual within-community reactions to their local environment, to ecologically complex synchronous community-wide response, accompanied by an increase in rates of origination. Subsequently, reef and archaeocyath body size are reduced in association with increased rates of extinction due to inferred expanded marine anoxia (~519&amp;#8211;516.5 Ma). The later oxic pulse at ~515 Ma shows further reef habitat expansion, increased archaeocyath body size and diversity, but weaker community-wide environmental responses.&lt;/p&gt; &lt;p&gt;These metrics confirm that oxygenation events created temporary pulses of evolutionary diversification and enhanced ecosystem complexity, potentially via the expansion of habitable space, and increased archaeocyath individual and reef longevity in turn leading to niche differentiation. Most notably, we show that progression towards increasing biodiversity and ecosystem complexity was episodic and discontinuous, rather than linear, during the Cambrian Radiation.&lt;/p&gt; &lt;p&gt;&amp;#160;&lt;/p&gt;
The timing of the first appearance of animals is of crucial importance for understanding the evol... more The timing of the first appearance of animals is of crucial importance for understanding the evolution of life on Earth. Although the fossil record places the earliest metazoans at 572–602 Ma, molecular clock studies suggest a far earlier origination, as far back as ~850 Ma. The difference in these dates would place the rise of animal life into a time period punctuated by multiple colossal, potentially global, glacial events. Although the two schools of thought debate the limitations of each other's methods, little time has been dedicated to how animal life might have survived if it did arise before or during these global glacial periods. The history of recent polar biota shows that organisms have found ways of persisting on and around the ice of the Antarctic continent throughout the Last Glacial Maximum (33–14 Ka), with some endemic species present before the breakup of Gondwana (180–23 Ma). Here we discuss the survival strategies and habitats of modern polar marine organisms ...
Los ejemplares de Dickinsonia de los Urales Centrales se caracterizan por una clara simetría bila... more Los ejemplares de Dickinsonia de los Urales Centrales se caracterizan por una clara simetría bilateral. Tomando en cuenta las observaciones de especímenes australianos, consideramos que la llamada’simetría de reflexión por deslizamiento’ en estos fósiles es un fenómeno tafonómico. El gráfico de distribución de frecuencias de tamaño muestra el predominio de individuos juveniles en la población estudiada de Dickinsonia de los Urales Centrales. Asumiendo que la edad de un individuo se manifiesta por su tamaño, existe un predominio significativo de individuos juveniles en la población. Se pueden prever tres escenarios posibles: (1) la población tiene un gran número de individuos juveniles como resultado de la alta tasa de supervivencia en la zona intermareal; (2) la población está dominada por formas juveniles porque está enterrada inmediatamente después de la eclosión; (3) suponiendo que Dickinsonia fuera un organismo móvil activo, la abundancia de individuos juveniles podría explicars...
The carotid bifurcation has been a region of particular interest due to its predilection for clin... more The carotid bifurcation has been a region of particular interest due to its predilection for clinically significant atherosclerosis. It has been shown that the vessel geometry is a major determinant of the local haemodynamic properties which are believed to be associated with the location of atherosclerotic lesions. Current knowledge of the geometry of the carotid bifurcation is insufficient and restricted to basic geometric parameters. To provide some means of quantifying the degree of complexity of the 3D shape of the bifurcation, we made an initial attempt by evaluating the non-planarity of an arterial bifurcation based upon the singular value decomposition theorem. In this paper we present our results obtained on the right carotid bifurcations of six normal subjects, each of whom was scanned twice using the 2D time-of-flight MR sequence. The acquired 2D cross sectional images were processed by using our in-house software which comprises 2D segmentation, 3D reconstruction and smo...
Oxygenation during the Cambrian Radiation progressed via a series of short-lived pulses. However,... more Oxygenation during the Cambrian Radiation progressed via a series of short-lived pulses. However, the metazoan biotic response to this episodic oxygenation has not been quantified, nor have the causal evolutionary processes been constrained. Here we present ecological analyses of Cambrian archaeocyath sponge reef communities on the Siberian Platform (525–514 Ma). During the oxic pulse at ~521–519 Ma, we quantify reef habitat expansion coupled to an increase in reef size and metacommunity complexity, from individual within-community reactions to their local environment, to ecologically complex synchronous community-wide response, accompanied by an increase in rates of origination. Subsequently, reef and archaeocyath body size are reduced in association with increased rates of extinction due to inferred expanded marine anoxia (~519–516.5 Ma). A later oxic pulse at ~515 Ma shows further reef habitat expansion, increased archaeocyath body size and diversity, but weaker community-wide en...
The broad-scale environment plays a substantial role in shaping modern marine ecosystems, but the... more The broad-scale environment plays a substantial role in shaping modern marine ecosystems, but the degree to which palaeocommunities were influenced by their environment is unclear. To investigate how broad-scale environment influenced the community ecology of early animal ecosystems we employed spatial point process analyses to examine the community structure of seven bedding-plane assemblages of late Ediacaran age (558–550 Ma), drawn from a range of environmental settings and global localities. The studied palaeocommunities exhibit marked differences in the response of their component taxa to sub-metre-scale habitat heterogeneities on the seafloor. Shallow-marine palaeocommunities were heavily influenced by local habitat heterogeneities, in contrast to their deep-water counterparts. Lower species richness in deep-water Ediacaran assemblages compared to shallow-water counterparts across the studied time-interval could have been driven by this environmental patchiness, because habita...
Trace fossils record foraging behaviors, the search for resources in patchy environments, of anim... more Trace fossils record foraging behaviors, the search for resources in patchy environments, of animals in the rock record. Quantification of the strength, density, and nature of foraging behaviors enables the investigation of how these may have changed through time. Here, we present a novel approach to explore such patterns using spatial point process analyses to quantify the scale and strength of ichnofossil spatial distributions on horizontal bedding planes. To demonstrate the utility of this approach, we use two samples from the terminal Ediacaran Shibantan Member in South China (between 551 and 543 Ma) and the early Cambrian Nagaur Sandstone in northwestern India (between 539 and 509 Ma). We find that ichnotaxa on both surfaces exhibited significant nonhomogeneous lateral patterns, with distinct levels of heterogeneity exhibited by different types of trace fossils. In the Shibantan, two ichnotaxa show evidence for mutual positive aggregation over a shared resource, suggesting the ...
Supplementary file 2: Base data, plotted data (graphical and maps), and analysis data. Plotted da... more Supplementary file 2: Base data, plotted data (graphical and maps), and analysis data. Plotted data and analysis data are derived from the base data, using formulae in Excel. These data and corresponding Excel formulae are presented in the following worksheets.
Pseudoplanktonic crinoid raft colonies are an enigma of the Jurassic. These raft colonies are tho... more Pseudoplanktonic crinoid raft colonies are an enigma of the Jurassic. These raft colonies are thought to have developed as floating filter-feeding communities due to an exceptionally rich oceanic niche, high in the water column enabling them to reach large densities on these log rafts. However, this pseudoplanktonic hypothesis has not been quantitatively tested, and there remains some doubt that this mode of life was possible. The ecological structure of the crinoid colony is resolved using spatial point process analyses and the duration estimates of the floating system until sinking using moisture diffusion models. Using spatial analysis, we found that the crinoids would have trailed preferentially positioned at the back of the floating log in the regions of least resistance, consistent with a floating, not benthic ecology. Additionally, we found using a series of moisture diffusion models at different log densities and sizes that ecosystem collapse did not take place solely due to...
Floating duration (in months) until sinking for small colonies [Göttingen (S1) and Stuttgart 1 (S... more Floating duration (in months) until sinking for small colonies [Göttingen (S1) and Stuttgart 1 (S2) – 40 cm long Diameter 5–6 cm (Community Removed); see Figure 3a] as a function of the dry density (g/cm3) of the material relative to water and its initial moisture content (%). In green wood, diffusion of moisture occurs longitudinally and radially (with a tangential component) for water vapour, liquid water bound to cell walls, and liquid water running free through vessels and tracheids . Initial moisture content reflects the humidity of the surrounding atmosphere (relative humidity) as well as its temperature, and moisture content constrains the diffusion coefficients. In green wood, moisture content can vary between sapwood (>100% where sap flows) and heartwood (~40% closer to the pith) but the model assumes an average moisture content throughout the log. The log will sink as soon as the system {wood log + water} is denser than water. For example (red dotted lines), a log with ...
Floating duration (in months) until critical mass for small colonies [Göttingen (S1) and Stuttgar... more Floating duration (in months) until critical mass for small colonies [Göttingen (S1) and Stuttgart 1 (S2) – 40 cm long Diameter 5–6 cm (Community Included); see Figure 3b] as a function of the dry density (g/cm3) of the material relative to water and its initial moisture content (%). In addition to the soaking process, we have loaded the log with a community of crinoids with an arbitrary individual growth rate extrapolated from extant species of Neocrinus decorus, Endoxocrinus parae and Cenocrinus asterius within [0.6–17.0 cm/yr] (Messing et al. 2007). Monthly growth rates were converted into mass increments using the specific gravity of calcite at 2.7g/cm3. The log will sink as soon as the system {wood log+water+crinoids} is denser than water. In this case, the log sinks at the end of the first monthly increment of growth.
Fig. S1: Locality map. Fig S2: Stratigraphic logs through the Russian sections. Fig S3: High reso... more Fig. S1: Locality map. Fig S2: Stratigraphic logs through the Russian sections. Fig S3: High resolution digitized map of KS surface. Fig S4: : Analyses of the size-distribution of <i>Funisia</i> populations
Floating duration (in months) until critical mass for medium colonies [Holzmaden (G1) and Stuttga... more Floating duration (in months) until critical mass for medium colonies [Holzmaden (G1) and Stuttgart 2 (G2) – 12 m long Diameter 25–28 cm (Community Removed); see Figure 3e] as a function of the dry density (g/cm3) of the material relative to water and its initial moisture content (%). For example, at fiber saturation (30% moisture content), a material of dry density of 0.4 g/cm3 would take approximately 800 months or 66 years (red dotted lines).
Pseudoplanktonic crinoid raft colonies are an enigma of the Jurassic. These raft colonies are tho... more Pseudoplanktonic crinoid raft colonies are an enigma of the Jurassic. These raft colonies are thought to have developed as floating filter-feeding communities due to an exceptionally rich oceanic niche, high in the water column enabling them to reach large densities on these log rafts. However, this pseudoplanktonic hypothesis has not been quantitatively tested, and there remains some doubt that this mode of life was possible. The ecological structure of the crinoid colony is resolved using spatial point process analyses and the duration estimates of the floating system until sinking using moisture diffusion models. Using spatial analysis, we found that the crinoids would have trailed preferentially positioned at the back of the floating log in the regions of least resistance, consistent with a floating, not benthic ecology. Additionally, we found using a series of moisture diffusion models at different log densities and sizes that ecosystem collapse did not take place solely due to...
Evidence for cysts and for ability for cell to change shape, from selected fossil assemblages spa... more Evidence for cysts and for ability for cell to change shape, from selected fossil assemblages spanning late Paleoproterozoic through Tonian time. Age constraints from [1] or as cited in references.
Robust time-series of direct observations of jellyfish abundance are not available for many ecosy... more Robust time-series of direct observations of jellyfish abundance are not available for many ecosystems, leaving it difficult to determine changes in jellyfish abundance, the possible causes (e.g. climate change) or the consequences (e.g. trophic cascades). We sought an indirect ecological route to reconstruct jellyfish abundance in the Irish Sea: since zooplankton are jellyfish prey, historic variability in zooplankton communities may provide proxies for jellyfish abundance. We determined the Bayesian ecological network of jellyfish–zooplankton dependencies using jellyfish- and zooplankton-abundance data obtained using nets during a 2-week cruise to the Irish Sea in 2008. This network revealed that Aurelia aurita abundance was dependent on zooplankton groups Warm Temperate and Temperate Oceanic as defined by previous zooplankton ecology work. We then determined historic zooplankton networks across the Irish Sea from abundance data from Continuous Plankton Recorder surveys conducted ...
Antarctic sea-floor communities are unique, and more closely resemble those of the Palaeozoic tha... more Antarctic sea-floor communities are unique, and more closely resemble those of the Palaeozoic than equivalent contemporary habitats. However, comparatively little is known about the processes that structure these communities or how they might respond to anthropogenic change. In order to investigate likely consequences of a decline or removal of key taxa on community dynamics we use Bayesian network inference to reconstruct ecological networks and infer changes of taxon removal. Here we show that sponges have the greatest influence on the dynamics of the Antarctic benthos. When we removed sponges from the network, the abundances of all major taxa reduced by a mean of 42%, significantly more than changes of substrate. To our knowledge, this study is the first to demonstrate the cascade effects of removing key ecosystem structuring organisms from statistical analyses of Antarctica data and demonstrates the importance of considering the community dynamics when planning ecosystem managem...
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