scholarly journals Neoproterozoic origin and multiple transitions to macroscopic growth in green seaweeds

2019 ◽  
Author(s):  
Andrea Del Cortona ◽  
Christopher J. Jackson ◽  
François Bucchini ◽  
Michiel Van Bel ◽  
Sofie D’hondt ◽  
...  
Keyword(s):  
Biotic Interactions ◽  
Grazing Pressure ◽  
Benthic Habitat ◽  
Evolutionary Origins ◽  
Early Diversification ◽  
Benthic Ecosystems ◽  
Fossil Data ◽  
Climate Events ◽  
Crucial Part ◽  
Neoproterozoic Era

AbstractThe Neoproterozoic Era records the transition from a largely bacterial to a predominantly eukaryotic phototrophic world, creating the foundation for the complex benthic ecosystems that have sustained Metazoa from the Ediacaran Period onward. This study focusses on the evolutionary origins of green seaweeds, which play an important ecological role in the benthos of modern sunlit oceans and likely played a crucial part in the evolution of early animals by structuring benthic habitats and providing novel niches. By applying a phylogenomic approach, we resolve deep relationships of the core Chlorophyta (Ulvophyceae or green seaweeds, and freshwater or terrestrial Chlorophyceae and Trebouxiophyceae) and unveil a rapid radiation of Chlorophyceae and the principal lineages of the Ulvophyceae late in the Neoproterozoic Era. Our time-calibrated tree points to an origin and early diversification of green seaweeds in the late Tonian and Cryogenian periods, an interval marked by two global glaciations, with strong consequent changes in the amount of available marine benthic habitat. We hypothesize that the unicellular and simple multicellular ancestors of green seaweeds survived these extreme climate events in isolated refugia, and diversified following recolonization of benthic environments that became increasingly available as sea ice retreated. An increased supply of nutrients and biotic interactions such as grazing pressure has likely triggered the independent evolution of macroscopic growth via different strategies, including both true multicellularity, and multiple types of giant celled forms.Significance StatementGreen seaweeds are important primary producers along coastlines worldwide, and likely played a key role in the evolution of animals. To understand their origin and diversification, we resolve key relationships among extant green algae using a phylotranscriptomic approach. We calibrate our tree using available fossil data, to reconstruct important evolutionary events such as transitions to benthic environments, and evolution of macroscopic growth. We estimate green seaweeds to have originated in the late Tonian/Cryogenian Period, followed by a marked Ordovician diversification of macroscopic forms. This ancient proliferation of green seaweeds likely modified shallow marine ecosystems, which set off an evolutionary arms race between ever larger seaweeds and grazers.

scholarly journals Neoproterozoic origin and multiple transitions to macroscopic growth in green seaweeds

2020 ◽  
Vol 117 (5) ◽  
pp. 2551-2559 ◽  
Author(s):  
Andrea Del Cortona ◽  
Christopher J. Jackson ◽  
François Bucchini ◽  
Michiel Van Bel ◽  
Sofie D’hondt ◽  
...  
Keyword(s):  
Biotic Interactions ◽  
Grazing Pressure ◽  
Benthic Habitat ◽  
Rapid Radiation ◽  
Evolutionary Origins ◽  
Early Diversification ◽  
Benthic Ecosystems ◽  
Climate Events ◽  
Crucial Part ◽  
Neoproterozoic Era

The Neoproterozoic Era records the transition from a largely bacterial to a predominantly eukaryotic phototrophic world, creating the foundation for the complex benthic ecosystems that have sustained Metazoa from the Ediacaran Period onward. This study focuses on the evolutionary origins of green seaweeds, which play an important ecological role in the benthos of modern sunlit oceans and likely played a crucial part in the evolution of early animals by structuring benthic habitats and providing novel niches. By applying a phylogenomic approach, we resolve deep relationships of the core Chlorophyta (Ulvophyceae or green seaweeds, and freshwater or terrestrial Chlorophyceae and Trebouxiophyceae) and unveil a rapid radiation of Chlorophyceae and the principal lineages of the Ulvophyceae late in the Neoproterozoic Era. Our time-calibrated tree points to an origin and early diversification of green seaweeds in the late Tonian and Cryogenian periods, an interval marked by two global glaciations with strong consequent changes in the amount of available marine benthic habitat. We hypothesize that unicellular and simple multicellular ancestors of green seaweeds survived these extreme climate events in isolated refugia, and diversified in benthic environments that became increasingly available as ice retreated. An increased supply of nutrients and biotic interactions, such as grazing pressure, likely triggered the independent evolution of macroscopic growth via different strategies, including true multicellularity, and multiple types of giant-celled forms.

Regional and environmental variation in escalatory ecological trends during the Jurassic: a western Tethys hotspot for escalation?

Paleobiology ◽  
2017 ◽  
Vol 43 (4) ◽  
pp. 569-586 ◽  
Author(s):  
Pedro M. Monarrez ◽  
Martin Aberhan ◽  
Steven M. Holland
Keyword(s):  
Regional Scale ◽  
Biotic Interactions ◽  
Environmental Variation ◽  
Global Scale ◽  
Depositional Environments ◽  
Western Tethys ◽  
Global Signal ◽  
Ecological Patterns ◽  
Taxonomic Groups ◽  
Fossil Data

AbstractUnderstanding the drivers of macroevolutionary trends through the Phanerozoic has been a central question in paleobiology. Increasingly important is understanding the regional and environmental variation of macroevolutionary patterns and how they are reflected at the global scale. Here we test the role of biotic interactions on regional ecological patterns during the Mesozoic marine revolution. We test for escalatory trends in Jurassic marine benthic macroinvertebrate ecosystems using occurrence data from the Paleobiology Database parsed by region and environment. The escalation hypothesis posits that taxonomic groups that could adapt to intense predation and bioturbation proliferated, whereas groups unable to adapt were reduced in diversity and abundance or driven to extinction. We tested this hypothesis in five regions during Jurassic stages and among four depositional environments in Europe. Few escalatory trends were detected, although at least one escalatory trend was observed in every region, with the greatest number and strongest trends observed in Europe. These trends include increases in shallow infauna and cementing epifauna and occurrences of facultatively mobile invertebrates and decreases in pedunculate, free-lying, and sessile epifauna. Within Europe, escalatory trends occur in shallow-water environments but also in deeper-water environments, where they are predicted not to occur. When regional trends are aggregated, trends in Europe drive the global signal. The results of this study suggest that while evidence of escalation is rare globally, it is plausible that escalation drove macroevolutionary patterns in Europe. Furthermore, these results underline the need to dissect global fossil data at the regional scale to understand global macroevolutionary dynamics.

scholarly journals Evolutionary origins and diversification of testis-specific short histone H2A variants in mammals

2017 ◽  
Author(s):  
Antoine Molaro ◽  
Janet M. Young ◽  
Harmit S. Malik
Keyword(s):  
Genome Stability ◽  
Histone Variants ◽  
Histone Variant ◽  
Histone H2a ◽  
Genetic Conflict ◽  
Post Translational Modifications ◽  
Evolutionary Origins ◽  
Male Germline ◽  
Early Diversification ◽  
Canonical Histone

Eukaryotic genomes must accomplish the tradeoff between compact packaging for genome stability and inheritance, and accessibility for gene expression. They do so using post-translational modifications of four ancient canonical histone proteins (H2A, H2B, H3 and H4), and by deploying histone variants with specialized chromatin functions. While some histone variants are highly conserved across eukaryotes, others carry out lineage-specific functions. Here, we characterize the evolution of male germline-specific “short H2A variants”, which wrap shorter DNA fragments than canonical H2A. In addition to three previously described H2A.B, H2A.L and H2A.P variants, we describe a novel, extremely short H2A histone variant: H2A.Q. We show that H2A.B, H2A.L, H2A.P and H2A.Q are most closely related to a novel, more canonical mmH2A variant found only in monotremes and marsupials. Using phylogenomics, we trace the origins and early diversification of short histone variants into four distinct clades to the ancestral X chromosome of placental mammals. We show that short H2A variants further diversified by repeated lineage-specific amplifications and losses, including pseudogenization of H2A.L in many primates. We also uncover evidence for concerted evolution of H2A.B and H2A.L genes by gene conversion in many species, involving loci separated by large distances. Finally, we find that short H2As evolve more rapidly than any other histone variant, with evidence that positive selection has acted upon H2A.P in primates. Based on their X chromosomal location and pattern of genetic innovation, we speculate that short H2A histone variants are engaged in a form of genetic conflict involving the mammalian sex chromosomes.

Section 1 Summary—Evolutionary Origins and Transitions in Developmental Mode

2018 ◽  
Keyword(s):  
Life Histories ◽  
Marine Invertebrates ◽  
Morphological Characteristics ◽  
Biotic Interactions ◽  
Reproductive Mode ◽  
Marine Species ◽  
Comparative Approach ◽  
Closely Related Species ◽  
Larval Stages ◽  
Evolutionary Origins

Abiotic variables and biotic interactions can act on variation in life history traits, ultimately leading to divergence in reproductive mode. Marine invertebrates have a remarkable diversity in such strategies, sometimes even between closely related species. It is this natural diversity that lends itself to employing a powerful comparative approach, both for particular morphological characteristics as well as molecular signatures from developmental genes. For example, complex life histories, where a larval stage is interposed between the embryo and juvenile, likely represent the product of numerous selection pressures, historical and current, that have shaped the diversity of larval stages in extant marine species. In fact, the very question about “what is a larva?” has to be addressed, as it is so intimately connected to bentho-planktonic life cycle and metamorphosis. Furthermore, novel larval types have evolved in particular lineages and larvae have been secondarily lost in others. This in itself creates an interesting and exciting playground to test evolutionary developmental hypotheses....

Environmental Stress Models

2003 ◽  
Author(s):  
M. E. J. Newman ◽  
R. G. Palmer
Keyword(s):  
Critical Phenomena ◽  
Power Law ◽  
Species Interactions ◽  
Fossil Record ◽  
Biotic Interactions ◽  
Power Laws ◽  
Fixed Number ◽  
Stress Models ◽  
Fossil Data ◽  
Power Law Distributions

In chapters 2 to 4 we discussed several models of extinction which make use of ideas drawn from the study of critical phenomena. The primary impetus for this approach was the observation of apparent power-law distributions in a variety of statistics drawn from the fossil record, as discussed in section 1.2; in other branches of science such power laws are often indicators of critical processes. However, there are also a number of other mechanisms by which power laws can arise, including random multiplicative processes (Montroll and Shlesinger 1982; Sornette and Cont 1997), extremal random processes (Sibani and Littlewood 1993), and random barrier-crossing dynamics (Sneppen 1995). Thus the existence of power-law distributions in the fossil data is not on its own sufficient to demonstrate the presence of critical phenomena in extinction processes. Critical models also assume that extinction is caused primarily by biotic effects such as competition and predation, an assumption which is in disagreement with the fossil record. As discussed in section 1.2.2.1, all the plausible causes for specific prehistoric extinctions are abiotic in nature. Therefore an obvious question to ask is whether it is possible to construct models in which extinction is caused by abiotic environmental factors, rather than by critical fluctuations arising out of biotic interactions, but which still give power-law distributions of the relevant quantities. Such models have been suggested by Newman (1996, 1997) and by Manrubia and Paczuski (1998). Interestingly, both of these models are the result of attempts at simplifying models based on critical phenomena. Newman's model is a simplification of the model of Newman and Roberts (see section 3.6), which included both biotic and abiotic effects; the simplification arises from the realization that the biotic part can be omitted without losing the power-law distributions. Manrubia and Paczuski's model was a simplification of the connection model of Solé and Manrubia (see section 4.1), but in fact all direct species-species interactions were dropped, leaving a model which one can regard as driven only by abiotic effects. We discuss these models in turn. The model proposed by Newman (1996, 1997) has a fixed number N of species which in the simplest case are noninteracting.

From feeding habits to food webs: exploring the diet of an opportunistic benthic generalist

2020 ◽  
Vol 655 ◽  
pp. 107-121
Author(s):  
AL van der Reis ◽  
AG Jeffs ◽  
SD Lavery
Keyword(s):  
Deep Sea ◽  
Fishery Management ◽  
Feeding Habits ◽  
Geographic Region ◽  
Trophic Relationships ◽  
Gut Contents ◽  
Benthic Habitat ◽  
Dna Metabarcoding ◽  
Benthic Ecosystems ◽  
Trophic Role

Deep-sea benthic ecosystems are difficult to study, particularly when trying to clarify diet and trophic relationships. New Zealand scampi Metanephrops challengeri are endemic, commercially prized deep-sea lobsters that are bottom trawled. These lobsters are typically the dominant mobile megafaunal species in the deep-sea benthic habitat, and their burrowing behaviour plays an important role in bioturbation of seafloor habitats. DNA metabarcoding was undertaken on the gut contents of 66 scampi from 4 fishery management areas using COI and 18S rRNA markers to better understand their feeding habits and trophic role. Scampi were confirmed to be opportunistic benthic scavengers, with the gut samples containing over 150 species, ranging from small (e.g. alveolates) to large eukaryotes (e.g. fish). The main dietary components consisted of crabs and prawns, but also included macroalgae and fish. Significant differences were found among scampi gut contents when comparing season and geographic region, but not when comparing sex and size. Due to their generalist scavenging nature, scampi play an important role in the deep-sea benthic ecosystems and are natural benthic samplers that are well suited to being used as deep-sea ecosystem/biodiversity monitors.

Deep-Water Ediacaran Fossils from Northwestern Canada: Taphonomy, Ecology, and Evolution

2014 ◽  
Vol 88 (2) ◽  
pp. 207-223 ◽  
Author(s):  
Guy M. Narbonne ◽  
Marc Laflamme ◽  
Peter W. Trusler ◽  
Robert W. Dalrymple ◽  
Carolyn Greentree
Keyword(s):  
Shallow Water ◽  
Deep Water ◽  
Evolutionary Origins ◽  
Ediacara Biota ◽  
Slope Deposits ◽  
Mackenzie Mountains ◽  
Fossil Data

Impressions of soft-bodied Ediacaran megafossils are common in deep-water slope deposits of the June beds at Sekwi Brook in the Mackenzie Mountains of NW Canada. Two taphonomic assemblages can be recognized. Soles of turbidite beds contain numerous impressions of simple (Aspidella) and tentaculate (Hiemalora, Eoporpita) discs. A specimen of the frond Primocandelabrum is attached to an Aspidella-like holdfast, but most holdfast discs lack any impressions of the leafy fronds to which they were attached, reflecting Fermeuse-style preservation of the basal level of the community. Epifaunal fronds (Beothukis, Charnia, Charniodiscus) and benthic recliners (Fractofusus) were most commonly preserved intrastratally on horizontal parting surfaces within turbidite and contourite beds, reflecting a deep-water example of Nama-style preservation of higher levels in the community. A well-preserved specimen of Namalia significantly extends the known age and environmental range of erniettomorphs into deep-water aphotic settings. Infaunal bilaterian burrows are absent from the June beds despite favorable beds for their preservation. The June beds assemblage is broadly similar in age and environment to deep-water Avalonian assemblages in Newfoundland and England, and like them contains mainly rangeomorph and arboreomorph fossils and apparently lacks dickinsoniomorphs and other clades typical of younger and shallower Ediacaran assemblages. Fossil data presently available imply that the classically deep- and shallow-water taxa of the Ediacara biota had different evolutionary origins and histories, with sessile rangeomorphs and arboreomorphs appearing in deep-water settings approximately 580 million years ago and spreading into shallow-water settings by 555 Ma but dickinsoniomorphs and other iconic clades restricted to shallow-water settings from their first known appearance at 555 Ma until their disappearance prior to the end of the Ediacaran.

The effect of preservation on diversity in a Triassic reef basin assemblage

2021 ◽  
Author(s):  
Vanessa Julie Roden ◽  
Alexander Nützel ◽  
Wolfgang Kiessling
Keyword(s):  
Biotic Interactions ◽  
Priority Effects ◽  
Late Triassic ◽  
Strong Increase ◽  
Predator Prey ◽  
Cassian Formation ◽  
Tropical Reef ◽  
Fossil Assemblages ◽  
Benthic Ecosystems ◽  
High Beta

<p>Taphonomic effects complicate the assessment of variations in biodiversity over time. Most pre-Cenozoic fossil assemblages have been altered through taphonomic effects, such as lithification and aragonite dissolution. Several studies have found alpha (local) and gamma (global) diversity in marine ecosystems to be low in the early Mesozoic and then increase throughout the Mesozoic, reaching a maximum in the Cenozoic.</p><p>The Middle to Late Triassic Cassian Formation, exposed in the Dolomites, Southern Alps, northern Italy, comprises tropical reef basin and transported platform assemblages characterized by high diversity and commonly excellent preservation of fossils. The Cassian Formation yields high alpha (mean species richness per locality: 96), beta (mean Jaccard dissimilarity: 0.95), and gamma (1421 invertebrate species) diversity. The high primary diversity is probably due to the tropical reef-associated setting, and its reduced taphonomic alteration caused 4.5 times higher biodiversity to be preserved than in comparable pre-Cenozoic settings. High beta diversity can be explained by the presence of various habitat types and may also have been driven by priority effects. The Cassian fauna, like most comparable modern ecosystems, features a large number of gastropods (39% of all invertebrates, 58% of mollusks are gastropods). Especially small species in the millimeter size range contribute to the large number of gastropod species in the Cassian Formation. Our results support the assumption that the Modern Evolutionary Fauna was already established early in the Mesozoic and that the scarcity of small gastropods in many fossil assemblages is a taphonomic phenomenon. This contradicts the view that the major radiation of gastropods and the generally very strong increase in biodiversity largely took place in the Cenozoic. We suggest that highly complex, gastropod-dominant marine benthic ecosystems are as old as Middle/Late Triassic, pointing to an earlier establishment of the Modern Evolutionary Fauna than previously assumed. An improved eco-space utilization by infaunalization and increased biotic interactions such as a predator/prey escalation may have contributed to the high biodiversity and may reflect early aspects of the Marine Mesozoic Revolution.</p>

scholarly journals Distribution of macroalgae in the area of Calvi (Corsica)

2021 ◽  
Vol 9 ◽  
Author(s):  
Lea Katz ◽  
Damien Sirjacobs ◽  
Sylvie Gobert ◽  
Pierre Lejeune ◽  
Bruno Danis
Keyword(s):  
Habitat Type ◽  
Marine Biodiversity ◽  
Benthic Habitat ◽  
Remotely Operated Vehicle ◽  
Invasive Algae ◽  
The Status ◽  
Caulerpa Prolifera ◽  
Benthic Ecosystems ◽  
Conservation Plans ◽  
Lower Limits

Macroalgae play a structuring role in benthic ecosystems, which makes it very important to monitor their cover rates and study their community structures and changes in time. Such studies are usually led by autonomous divers and often do not generate sufficient data to provide enough material for strategically-sound conservation plans. This paper describes the dataset generated in the framework of the evaluation of the potential of a complementary data acquisition method: annotating videos transects obtained using an underwater Remotely Operated Vehicle (ROV). The focus was on Cystoseira brachycarpa, together with the abundance of several other macroalgae species, which could be identified using the ROV images after validation through specimen identification. Furthermore, in order to allow future uses, such as monitoring the status of colonisation of the invasive algae Caulerpa cylindracea, the ROV was sent to some deeper transects on sedimentary habitats (40 m) below the Posidonia meadows lower limits. The project, while providing some interesting insights on using a ROV as a tool to study marine biodiversity, generated a dataset for the distribution of 19 macroalgae on both standardised and new transects in the Bay of Calvi (Katz et al. 2021). The observed species of macroalgae included: Acetabularia acetabulum, Amphiroa rigida, Caulerpa prolifera, Caulerpa cylindracea, Codium bursa, Colpomenia sinuosa, Corallinales (order), Cystoseira brachycarpa, Cystoseira crinita, Cystoseira spinosa, Cystoseira zosteroides, Dictyota (genus), Flabellia petiolata, Halopteris (genus), Halopteris scoparia, Jania (genus), Osmundaria volubilis, Padina pavonica and Peyssonnelia squamaria. The videos also showed that the invasive algae Caulerpa cylindracea has spread between 2016 and 2019 and that more focused studies should be held in the Bay to assess the actual reach and possible impacts of this invasion. Finally, our ROV video transects have also underlined the significant presence of particular benthic macroalgae communities over habitat zones described as "soft-bottom" on benthic habitat maps. Although the biomass per unit area of these communities is probably lower than for most coastal rocky bottoms, this widely-spread habitat type holds a contribution to primary production to be considered in coastal ecosystem models.

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