1
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Stephenson NP, Delahooke KM, Barnes N, Rideout BWT, Kenchington CG, Manica A, Mitchell EG. Morphology shapes community dynamics in early animal ecosystems. Nat Ecol Evol 2024; 8:1238-1247. [PMID: 38867093 PMCID: PMC11239517 DOI: 10.1038/s41559-024-02422-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 04/24/2024] [Indexed: 06/14/2024]
Abstract
The driving forces behind the evolution of early metazoans are not well understood, but key insights into their ecology and evolution can be gained through ecological analyses of the in situ, sessile communities of the Avalon assemblage in the Ediacaran (~565 million years ago). Community structure in the Avalon is thought to be underpinned by epifaunal tiering and ecological succession, which we investigate in this study in 18 Avalon communities. Here we found that Avalon communities form four distinctive Community Types irrespective of succession processes, which are instead based on the dominance of morphologically distinct taxa, and that tiering is prevalent in three of these Community Types. Our results are consistent with emergent neutrality, whereby ecologically specialized morphologies evolve as a consequence of neutral (stochastic or reproductive) processes within niches, leading to generalization within the frond-dominated Community Type. Our results provide an ecological signature of the first origination and subsequent loss of disparate morphologies, probably as a consequence of community restructuring in response to ecological innovation. This restructuring led to the survival of non-tiered frondose generalists over tiered specialists, even into the youngest Ediacaran assemblages. Such frondose body plans also survive beyond the Ediacaran-Cambrian transition, perhaps due to the greater resilience afforded to them by their alternative ecological strategies.
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Affiliation(s)
- Nile P Stephenson
- Department of Zoology, University of Cambridge, Cambridge, UK.
- University Museum of Zoology, University of Cambridge, Cambridge, UK.
| | - Katie M Delahooke
- Department of Earth Sciences, University of Cambridge, Cambridge, UK
| | | | | | | | - Andrea Manica
- Department of Zoology, University of Cambridge, Cambridge, UK
| | - Emily G Mitchell
- Department of Zoology, University of Cambridge, Cambridge, UK
- University Museum of Zoology, University of Cambridge, Cambridge, UK
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2
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Gutarra S, Mitchell EG, Dunn FS, Gibson BM, Racicot RA, Darroch SAF, Rahman IA. Ediacaran marine animal forests and the ventilation of the oceans. Curr Biol 2024; 34:2528-2534.e3. [PMID: 38761801 DOI: 10.1016/j.cub.2024.04.059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 03/18/2024] [Accepted: 04/25/2024] [Indexed: 05/20/2024]
Abstract
The rise of animals across the Ediacaran-Cambrian transition marked a step-change in the history of life, from a microbially dominated world to the complex macroscopic biosphere we see today.1,2,3 While the importance of bioturbation and swimming in altering the structure and function of Earth systems is well established,4,5,6 the influence of epifaunal animals on the hydrodynamics of marine environments is not well understood. Of particular interest are the oldest "marine animal forests,"7 which comprise a diversity of sessile soft-bodied organisms dominated by the fractally branching rangeomorphs.8,9 Typified by fossil assemblages from the Ediacaran of Mistaken Point, Newfoundland,8,10,11 these ancient communities might have played a pivotal role in structuring marine environments, similar to modern ecosystems,7,12,13 but our understanding of how they impacted fluid flow in the water column is limited. Here, we use ecological modeling and computational flow simulations to explore how Ediacaran marine animal forests influenced their surrounding environment. Our results reveal how organism morphology and community structure and composition combined to impact vertical mixing of the surrounding water. We find that Mistaken Point communities were capable of generating high-mixing conditions, thereby likely promoting gas and nutrient transport within the "canopy." This mixing could have served to enhance local-scale oxygen concentrations and redistribute resources like dissolved organic carbon. Our work suggests that Ediacaran marine animal forests may have contributed to the ventilation of the oceans over 560 million years ago, well before the Cambrian explosion of animals.
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Affiliation(s)
| | - Emily G Mitchell
- Department of Zoology, University Museum of Zoology Cambridge, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Frances S Dunn
- Oxford University Museum of Natural History, University of Oxford, Oxford OX1 3PW, UK
| | - Brandt M Gibson
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada; Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN 37240, USA
| | | | | | - Imran A Rahman
- The Natural History Museum, London SW7 5BD, UK; Oxford University Museum of Natural History, University of Oxford, Oxford OX1 3PW, UK.
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3
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Delahooke KM, Liu AG, Stephenson NP, Mitchell EG. 'Conga lines' of Ediacaran fronds: insights into the reproductive biology of early metazoans. ROYAL SOCIETY OPEN SCIENCE 2024; 11:231601. [PMID: 39076788 PMCID: PMC11286166 DOI: 10.1098/rsos.231601] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 02/29/2024] [Accepted: 04/09/2024] [Indexed: 07/31/2024]
Abstract
Late Ediacaran strata from Newfoundland, Canada (~574-560 Ma) document near-census palaeocommunities of some of the earliest metazoans. Such preservation enables reproductive strategies to be inferred from the spatial distribution of populations of fossilized benthic organisms, previously revealing the existence of both propagule and stoloniferous reproductive modes among Ediacaran frondose taxa. Here, we describe 'conga lines': linear arrangements of more than three closely spaced fossil specimens. We calculate probabilistic models of point maps of 13 fossil-bearing bedding surfaces and show that four surfaces contain conga lines that are not the result of chance alignments. We then test whether these features could result from passive pelagic propagules settling in the lee of an existing frond, using computational fluid dynamics and discrete phase modelling. Under Ediacaran palaeoenvironmental conditions, preferential leeside settlement at the spatial scale of the conga lines is unlikely. We therefore conclude that these features are novel and do not reflect previously described reproductive strategies employed by Ediacaran organisms, suggesting the use of mixed reproductive strategies in the earliest animals. Such strategies enabled Ediacaran frondose taxa to act as reproductive generalists and may be an important facet of early metazoan evolution.
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Affiliation(s)
| | - Alexander G. Liu
- Department of Earth Sciences, University of Cambridge, Cambridge, UK
| | - Nile P. Stephenson
- Department of Zoology, University of Cambridge, Cambridge, UK
- Museum of Zoology, University of Cambridge, Cambridge, UK
| | - Emily G. Mitchell
- Department of Zoology, University of Cambridge, Cambridge, UK
- Museum of Zoology, University of Cambridge, Cambridge, UK
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4
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Mussini G, Dunn FS. Decline and fall of the Ediacarans: late-Neoproterozoic extinctions and the rise of the modern biosphere. Biol Rev Camb Philos Soc 2024; 99:110-130. [PMID: 37667585 DOI: 10.1111/brv.13014] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 08/22/2023] [Accepted: 08/25/2023] [Indexed: 09/06/2023]
Abstract
The end-Neoproterozoic transition marked a gradual but permanent shift between distinct configurations of Earth's biosphere. This interval witnessed the demise of the enigmatic Ediacaran Biota, ushering in the structured trophic webs and disparate animal body plans of Phanerozoic ecosystems. However, little consensus exists on the reality, drivers, and macroevolutionary implications of end-Neoproterozoic extinctions. Here we evaluate potential drivers of late-Neoproterozoic turnover by addressing recent findings on Ediacaran geochronology, the persistence of classical Ediacaran macrobionts into the Cambrian, and the existence of Ediacaran crown-group eumetazoans. Despite renewed interest in the possibility of Phanerozoic-style 'mass extinctions' in the latest Neoproterozoic, our synthesis of the available evidence does not support extinction models based on episodic geochemical triggers, nor does it validate simple ecological interpretations centred on direct competitive displacement. Instead, we argue that the protracted and indirect effects of early bilaterian innovations, including escalations in sediment engineering, predation, and the largely understudied impacts of reef-building, may best account for the temporal structure and possible selectivity of late-Neoproterozoic extinctions. We integrate these processes into a generalised model of early eumetazoan-dominated ecologies, charting the disruption of spatial and temporal isotropy on the Ediacaran benthos as a consequence of diversifying macrofaunal interactions. Given the nature of resource distribution in Ediacaran ecologies, the continuities among Ediacaran and Cambrian faunas, and the convergent origins of ecologically disruptive innovations among bilaterians we suggest that the rise of Phanerozoic-type biotas may have been unstoppable.
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Affiliation(s)
- Giovanni Mussini
- Department of Earth Sciences, Downing Street, University of Cambridge, Cambridge, CB2 3EQ, UK
| | - Frances S Dunn
- Oxford University Museum of Natural History, Parks Road, University of Oxford, Oxford, OX1 3PW, UK
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5
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Darroch SA, Gutarra S, Masaki H, Olaru A, Gibson BM, Dunn FS, Mitchell EG, Racicot RA, Burzynski G, Rahman IA. The rangeomorph Pectinifrons abyssalis: Hydrodynamic function at the dawn of animal life. iScience 2023; 26:105989. [PMID: 36756377 PMCID: PMC9900436 DOI: 10.1016/j.isci.2023.105989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 12/06/2022] [Accepted: 01/12/2023] [Indexed: 01/18/2023] Open
Abstract
Rangeomorphs are among the oldest putative eumetazoans known from the fossil record. Establishing how they fed is thus key to understanding the structure and function of the earliest animal ecosystems. Here, we use computational fluid dynamics to test hypothesized feeding modes for the fence-like rangeomorph Pectinifrons abyssalis, comparing this to the morphologically similar extant carnivorous sponge Chondrocladia lyra. Our results reveal complex patterns of flow around P. abyssalis unlike those previously reconstructed for any other Ediacaran taxon. Comparisons with C. lyra reveal substantial differences between the two organisms, suggesting they converged on a similar fence-like morphology for different functions. We argue that the flow patterns recovered for P. abyssalis do not support either a suspension feeding or osmotrophic feeding habit. Instead, our results indicate that rangeomorph fronds may represent organs adapted for gas exchange. If correct, this interpretation could require a dramatic reinterpretation of the oldest macroscopic animals.
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Affiliation(s)
- Simon A.F. Darroch
- Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN 37240, USA,Evolutionary Studies Institute, Vanderbilt University, Nashville, TN 37235, USA,Senckenberg Research Institute and Natural History Museum Frankfurt, 60325 Frankfurt, Germany
| | | | - Hale Masaki
- Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN 37240, USA
| | - Andrei Olaru
- Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN 37240, USA
| | - Brandt M. Gibson
- Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN 37240, USA,Department of Chemistry and Physical Sciences, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
| | - Frances S. Dunn
- Oxford University Museum of Natural History, University of Oxford, Oxford OX1 3PW, UK
| | - Emily G. Mitchell
- Department of Zoology, Museum of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Rachel A. Racicot
- Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN 37240, USA,Evolutionary Studies Institute, Vanderbilt University, Nashville, TN 37235, USA,Senckenberg Research Institute and Natural History Museum Frankfurt, 60325 Frankfurt, Germany
| | - Gregory Burzynski
- Department of Biology, Fairfield University, Fairfield, CT 06824, USA
| | - Imran A. Rahman
- The Natural History Museum, London SW7 5BD, UK,Oxford University Museum of Natural History, University of Oxford, Oxford OX1 3PW, UK,Corresponding author
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6
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Griffiths HJ, Whittle RJ, Mitchell EG. Animal survival strategies in Neoproterozoic ice worlds. GLOBAL CHANGE BIOLOGY 2023; 29:10-20. [PMID: 36220153 PMCID: PMC10091762 DOI: 10.1111/gcb.16393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 07/25/2022] [Accepted: 08/09/2022] [Indexed: 06/16/2023]
Abstract
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 in environments analogous to those that could have existed during Neoproterozoic glaciations. We discuss how, despite the apparent harshness of many ice covered, sub-zero, Antarctic marine habitats, animal life thrives on, in and under the ice. Ice dominated systems and processes make some local environments more habitable through water circulation, oxygenation, terrigenous nutrient input and novel habitats. We consider how the physical conditions of Neoproterozoic glaciations would likely have dramatically impacted conditions for potential life in the shallows and erased any possible fossil evidence from the continental shelves. The recent glacial cycle has driven the evolution of Antarctica's unique fauna by acting as a "diversity pump," and the same could be true for the late Proterozoic and the evolution of animal life on Earth, and the existence of life elsewhere in the universe on icy worlds or moons.
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7
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Eden R, Manica A, Mitchell EG. Metacommunity analyses show an increase in ecological specialisation throughout the Ediacaran period. PLoS Biol 2022; 20:e3001289. [PMID: 35580078 PMCID: PMC9113585 DOI: 10.1371/journal.pbio.3001289] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Accepted: 03/29/2022] [Indexed: 11/18/2022] Open
Abstract
The first animals appear during the late Ediacaran (572 to 541 Ma); an initial diversity increase was followed reduction in diversity, often interpreted as catastrophic mass extinction. We investigate Ediacaran ecosystem structure changes over this time period using the “Elements of Metacommunity Structure” framework to assess whether this diversity reduction in the Nama was likely caused by an external mass extinction, or internal metacommunity restructuring. The oldest metacommunity was characterised by taxa with wide environmental tolerances, and limited specialisation or intertaxa associations. Structuring increased in the second oldest metacommunity, with groups of taxa sharing synchronous responses to environmental gradients, aggregating into distinct communities. This pattern strengthened in the youngest metacommunity, with communities showing strong environmental segregation and depth structure. Thus, metacommunity structure increased in complexity, with increased specialisation and resulting in competitive exclusion, not a catastrophic environmental disaster, leading to diversity loss in the terminal Ediacaran. These results reveal that the complex eco-evolutionary dynamics associated with Cambrian diversification were established in the Ediacaran. This study shows that the eco-evolutionary dynamics of metazoan diversification known from the Cambrian Period started earlier in the Ediacaran Period with the Avalon assemblage and increased in complexity towards the Phanerozoic as new anatomical innovations appeared, culminating in the “Cambrian Explosion."
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Affiliation(s)
- Rebecca Eden
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
| | - Andrea Manica
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
| | - Emily G. Mitchell
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
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8
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Ge Y, Meng X, Heino J, García‐Girón J, Liu Y, Li Z, Xie Z. Stochasticity overrides deterministic processes in structuring macroinvertebrate communities in a plateau aquatic system. Ecosphere 2021. [DOI: 10.1002/ecs2.3675] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Affiliation(s)
- Yihao Ge
- The Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology Chinese Academy of Sciences Wuhan China
- University of Chinese Academy of Sciences Beijing China
| | - Xingliang Meng
- The Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology Chinese Academy of Sciences Wuhan China
| | - Jani Heino
- Freshwater Centre Finnish Environment Institute Paavo Havaksen Tie 3P.O. Box 413 Oulu FI‐90014 Finland
| | - Jorge García‐Girón
- Group for Limnology and Environmental Biotechnology Area of Ecology Universidad de León Campus de Vegazana León Spain
| | - Yang Liu
- The Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology Chinese Academy of Sciences Wuhan China
- University of Chinese Academy of Sciences Beijing China
| | - Zhengfei Li
- The Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology Chinese Academy of Sciences Wuhan China
| | - Zhicai Xie
- The Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology Chinese Academy of Sciences Wuhan China
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9
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Swain A, Devereux M, Fagan WF. Deciphering trophic interactions in a mid-Cambrian assemblage. iScience 2021; 24:102271. [PMID: 33817576 PMCID: PMC8010449 DOI: 10.1016/j.isci.2021.102271] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 12/07/2020] [Accepted: 03/02/2021] [Indexed: 11/23/2022] Open
Abstract
Exceptionally preserved fossil sites have allowed specimen-based identification of trophic interactions to which network analyses have been applied. However, network analyses of the fossil record suffer from incomplete and indirect data, time averaging that obscures species coexistence, and biases in preservation. Here, we present a high-resolution fossil data set from Raymond Quarry member of the mid-Cambrian Burgess Shale (7,549 specimens, 61 taxa, ∼510 Mya) and formulate a measure of "preservation bias" that aids identification of assemblage subsets to which network analyses can be reliably applied. For these sections, abundance correlation network analyses predicted longitudinally consistent trophic and competitive interactions. Our analyses predicted previously postulated trophic interactions with 83.5% accuracy and demonstrated a shift from specialist interaction-dominated assemblages to ones dominated by generalist and competitive interactions. This approach provides a robust, taphonomically corrected framework to explore and predict in detail the existence and ecological character of putative interactions in fossil data sets.
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Affiliation(s)
- Anshuman Swain
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Matthew Devereux
- Department of Earth Science, Western University, London, ON, Canada
| | - William F. Fagan
- Department of Biology, University of Maryland, College Park, MD 20742, USA
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10
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Boom-bust population dynamics increase diversity in evolving competitive communities. Commun Biol 2021; 4:502. [PMID: 33893395 PMCID: PMC8065032 DOI: 10.1038/s42003-021-02021-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Accepted: 03/24/2021] [Indexed: 11/24/2022] Open
Abstract
The processes and mechanisms underlying the origin and maintenance of biological diversity have long been of central importance in ecology and evolution. The competitive exclusion principle states that the number of coexisting species is limited by the number of resources, or by the species’ similarity in resource use. Natural systems such as the extreme diversity of unicellular life in the oceans provide counter examples. It is known that mathematical models incorporating population fluctuations can lead to violations of the exclusion principle. Here we use simple eco-evolutionary models to show that a certain type of population dynamics, boom-bust dynamics, can allow for the evolution of much larger amounts of diversity than would be expected with stable equilibrium dynamics. Boom-bust dynamics are characterized by long periods of almost exponential growth (boom) and a subsequent population crash due to competition (bust). When such ecological dynamics are incorporated into an evolutionary model that allows for adaptive diversification in continuous phenotype spaces, desynchronization of the boom-bust cycles of coexisting species can lead to the maintenance of high levels of diversity. Michael Doebeli et al. introduce a discrete-time competition model with multi-dimensional evolving phenotypes to explore the effect of boom-bust population dynamics on the evolution of diversity. Their models show that long periods of near-exponential growth, followed by a population crash due to competition, can lead to the origin and maintenance of high levels of diversity in competitive communities.
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11
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Brian JI, Aldridge DC. Abundance data applied to a novel model invertebrate host shed new light on parasite community assembly in nature. J Anim Ecol 2021; 90:1096-1108. [PMID: 33522596 DOI: 10.1111/1365-2656.13436] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 01/08/2021] [Indexed: 11/29/2022]
Abstract
Understanding how environmental drivers influence the assembly of parasite communities, in addition to how parasites may interact at an infracommunity level, are fundamental requirements for the study of parasite ecology. Knowledge of how parasite communities are assembled will help to predict the risk of parasitism for hosts, and model how parasite communities may change under variable conditions. However, studies frequently rely on presence-absence data and examine multiple host species or sites, metrics which may be too coarse to characterise nuanced within-host patterns. We utilised a novel host system, the freshwater mussel Anodonta anatina, to investigate the drivers of community structure and explore parasite interactions. In addition, we aimed to highlight consistencies and inconsistencies between PA and abundance data. Our analysis incorporated 14 parasite taxa and 720 replicate infracommunities. Using Redundancy Analysis, a joint species distribution model and a Markov random field approach, we modelled the impact of both host-level and environment-level characteristics on parasite structure, as well as parasite-parasite correlations after accounting for all other factors. This approach was repeated for both the presence and abundance of all parasites. We demonstrated that the regional species pool, individual host characteristics (mussel length and gravidity) and predicted parasite-parasite interactions are all important but to varying degrees across parasite species, suggesting that applying generalities to parasite community construction is too simplistic. Furthermore, we showed that PA data fail to capture important density-dependent effects of parasite load for parasites with high abundance, and in general performs poorly for high-intensity parasites. Host and parasite traits, as well as broader environmental factors, all contribute to parasite community structure, emphasising that an integrated approach is required to study community assembly. However, care must be taken with the data used to infer patterns, as presence-absence data may lead to incorrect ecological inference.
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Affiliation(s)
- Joshua I Brian
- Aquatic Ecology Group, The David Attenborough Building, Department of Zoology, University of Cambridge, Cambridge, UK
| | - David C Aldridge
- Aquatic Ecology Group, The David Attenborough Building, Department of Zoology, University of Cambridge, Cambridge, UK
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12
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Hunter AW, Casenove D, Mayers C, Mitchell EG. Reconstructing the ecology of a Jurassic pseudoplanktonic raft colony. ROYAL SOCIETY OPEN SCIENCE 2020; 7:200142. [PMID: 32874621 PMCID: PMC7428219 DOI: 10.1098/rsos.200142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Accepted: 06/13/2020] [Indexed: 06/11/2023]
Abstract
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 colonies becoming overladen as previously assumed. Our analyses have found that these crinoid colonies studied could have existed for more than 10 years, even up to 20 years, exceeding the life expectancy of modern documented raft systems with possible implications for the role of modern raft communities in the biotic colonization of oceanic islands and intercontinental dispersal of marine and terrestrial species.
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Affiliation(s)
- Aaron W. Hunter
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK
- School of Earth Sciences, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
| | - David Casenove
- Graduate School of Nursing, Chiba University, 1-8-1, Inohana, Chuo-ku, Chiba-shi, Chiba 260-8672, Japan
| | - Celia Mayers
- Department of Applied Geology, Curtin University, Perth, Western Australia, Australia
| | - Emily G. Mitchell
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
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13
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Mitchell EG, Bobkov N, Bykova N, Dhungana A, Kolesnikov AV, Hogarth IRP, Liu AG, Mustill TMR, Sozonov N, Rogov VI, Xiao S, Grazhdankin DV. The influence of environmental setting on the community ecology of Ediacaran organisms. Interface Focus 2020; 10:20190109. [PMID: 32642052 DOI: 10.1098/rsfs.2019.0109] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/14/2020] [Indexed: 11/12/2022] Open
Abstract
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 (SPPA) to examine the community structure of seven late Ediacaran (558-550 Ma) bedding-plane assemblages 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 (nearshore) palaeocommunities were heavily influenced by local habitat heterogeneities, in contrast to their deeper-water counterparts. The local patchiness within shallow-water communities may have been further accentuated by the presence of grazers and detritivores, whose behaviours potentially initiated a propagation of increasing habitat heterogeneity of benthic communities from shallow to deep-marine depositional environments. Higher species richness in shallow-water Ediacaran assemblages compared to deep-water counterparts across the studied time-interval could have been driven by this environmental patchiness, because habitat heterogeneities increase species richness in modern marine environments. Our results provide quantitative support for the 'Savannah' hypothesis for early animal diversification-whereby Ediacaran diversification was driven by patchiness in the local benthic environment.
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Affiliation(s)
- Emily G Mitchell
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
| | - Nikolai Bobkov
- Trofimuk Institute of Petroleum Geology and Geophysics, 3, Ac. Koptyuga ave., Novosibirsk 630090, Russian Federation.,Novosibirsk State University, Novosibirsk, Novosibirsk Oblast 630090, Russian Federation
| | - Natalia Bykova
- Trofimuk Institute of Petroleum Geology and Geophysics, 3, Ac. Koptyuga ave., Novosibirsk 630090, Russian Federation.,Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, USA
| | - Alavya Dhungana
- Department of Earth Sciences, Durham University, Lower Mountjoy, South Road, Durham DH1 3LE, UK
| | - Anton V Kolesnikov
- Trofimuk Institute of Petroleum Geology and Geophysics, 3, Ac. Koptyuga ave., Novosibirsk 630090, Russian Federation.,Geological Institute, Russian Academy of Sciences, Pygevsky 7, Moscow 119017, Russia.,Faculty of Geography, Moscow State Pedagogical University, Kibalchicha str. 16, Moscow 129626, Russia
| | - Ian R P Hogarth
- Department of Chemical Engineering, University of Cambridge, Philippa Fawcett Drive, Cambridge CB3 0AS, UK
| | - Alexander G Liu
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK
| | - Tom M R Mustill
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK
| | - Nikita Sozonov
- Trofimuk Institute of Petroleum Geology and Geophysics, 3, Ac. Koptyuga ave., Novosibirsk 630090, Russian Federation.,Novosibirsk State University, Novosibirsk, Novosibirsk Oblast 630090, Russian Federation
| | - Vladimir I Rogov
- Trofimuk Institute of Petroleum Geology and Geophysics, 3, Ac. Koptyuga ave., Novosibirsk 630090, Russian Federation
| | - Shuhai Xiao
- Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, USA
| | - Dmitriy V Grazhdankin
- Trofimuk Institute of Petroleum Geology and Geophysics, 3, Ac. Koptyuga ave., Novosibirsk 630090, Russian Federation.,Novosibirsk State University, Novosibirsk, Novosibirsk Oblast 630090, Russian Federation
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