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"Vertebrates - classification"
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Animal school : what class are you?
Characteristics of the five vertebrate classes--mammal, bird, fish, reptile, and amphibian--are described along with illustrations reminiscent of woodcuts.
Book
A cold-blooded view of adaptive immunity
The adaptive immune system arose 500 million years ago in ectothermic (cold-blooded) vertebrates. Classically, the adaptive immune system has been defined by the presence of lymphocytes expressing recombination-activating gene (RAG)-dependent antigen receptors and the MHC. These features are found in all jawed vertebrates, including cartilaginous and bony fish, amphibians and reptiles and are most likely also found in the oldest class of jawed vertebrates, the extinct placoderms. However, with the discovery of an adaptive immune system in jawless fish based on an entirely different set of antigen receptors — the variable lymphocyte receptors — the divergence of T and B cells, and perhaps innate-like lymphocytes, goes back to the origin of all vertebrates. This Review explores how recent developments in comparative immunology have furthered our understanding of the origins and function of the adaptive immune system.
Journal Article
Global priorities for an effective information basis of biodiversity distributions
Gaps in digital accessible information (DAI) on species distributions hamper prospects of safeguarding biodiversity and ecosystem services, and addressing central ecological and evolutionary questions. Achieving international targets on biodiversity knowledge requires that information gaps be identified and actions prioritized. Integrating 157 million point records and distribution maps for 21,170 terrestrial vertebrate species, we find that outside a few well-sampled regions, DAI on point occurrences provides very limited and spatially biased inventories of species. Surprisingly, many large, emerging economies are even more under-represented in global DAI than species-rich, developing countries in the tropics. Multi-model inference reveals that completeness is mainly limited by distance to researchers, locally available research funding and participation in data-sharing networks, rather than transportation infrastructure, or size and funding of Western data contributors as often assumed. Our results highlight the urgent need for integrating non-Western data sources and intensifying cooperation to more effectively address societal biodiversity information needs.
Comprehensive digital information on species distributions is crucial for research in ecology, evolution and conservation. Here, Meyer
et al.
find large gaps and biases in global vertebrate point records, especially in emerging economies, and identify key factors currently limiting information.
Journal Article
Vertebrates on the brink as indicators of biological annihilation and the sixth mass extinction
The ongoing sixth mass species extinction is the result of the destruction of component populations leading to eventual extirpation of entire species. Populations and species extinctions have severe implications for society through the degradation of ecosystem services. Here we assess the extinction crisis from a different perspective. We examine 29,400 species of terrestrial vertebrates, and determine which are on the brink of extinction because they have fewer than 1,000 individuals. There are 515 species on the brink (1.7% of the evaluated vertebrates). Around 94% of the populations of 77 mammal and bird species on the brink have been lost in the last century. Assuming all species on the brink have similar trends, more than 237,000 populations of those species have vanished since 1900. We conclude the human-caused sixth mass extinction is likely accelerating for several reasons. First, many of the species that have been driven to the brink will likely become extinct soon. Second, the distribution of those species highly coincides with hundreds of other endangered species, surviving in regions with high human impacts, suggesting ongoing regional biodiversity collapses. Third, close ecological interactions of species on the brink tend to move other species toward annihilation when they disappear—extinction breeds extinctions. Finally, human pressures on the biosphere are growing rapidly, and a recent example is the current coronavirus disease 2019 (Covid-19) pandemic, linked to wildlife trade. Our results reemphasize the extreme urgency of taking much-expanded worldwide actions to save wild species and humanity’s crucial life-support systems from this existential threat.
Journal Article
The origins of acoustic communication in vertebrates
Acoustic communication is crucial to humans and many other tetrapods, including birds, frogs, crocodilians, and mammals. However, large-scale patterns in its evolution are largely unstudied. Here, we address several fundamental questions about the origins of acoustic communication in terrestrial vertebrates (tetrapods), using phylogenetic methods. We show that origins of acoustic communication are significantly associated with nocturnal activity. We find that acoustic communication does not increase diversification rates, a surprising result given the many speciation-focused studies of frog calls and bird songs. We also demonstrate that the presence of acoustic communication is strongly conserved over time. Finally, we find that acoustic communication evolved independently in most major tetrapod groups, often with remarkably ancient origins (~100–200 million years ago). Overall, we show that the role of ecology in shaping signal evolution applies to surprisingly deep timescales, whereas the role of signal evolution in diversification may not.
Acoustic communication is widespread, but not universal, across terrestrial vertebrates. Here, the authors show that acoustic communication evolved anciently, but independently, in most tetrapod groups and that these origins were associated with nocturnal activity.
Journal Article
Animal invaders threaten protected areas worldwide
Protected areas are the cornerstone of biodiversity conservation. However, alien species invasion is an increasing threat to biodiversity, and the extent to which protected areas worldwide are resistant to incursions of alien species remains poorly understood. Here, we investigate establishment by 894 terrestrial alien animals from 11 taxonomic groups including vertebrates and invertebrates across 199,957 protected areas at the global scale. We find that <10% of protected areas are home to any of the alien animals, but there is at least one established population within 10-100 km of the boundaries of 89%-99% of protected areas, while >95% of protected areas are environmentally suitable for establishment. Higher alien richness is observed in IUCN category-II national parks supposedly with stricter protection, and in larger protected areas with higher human footprint and more recent designation. Our results demonstrate that protected areas provide important protection from biological invasions, but invasions may become an increasingly dominant problem in the near future.
Safeguarding protected areas from invasive species is recognised as a global conservation objective. Here, Liu et al. analyse the occurrence of terrestrial alien animal invaders in protected areas and potential drivers globally, suggesting an impending risk for uninvaded protected areas in absence of preventive actions.
Journal Article
The evolutionary history of vertebrate RNA viruses
Our understanding of the diversity and evolution of vertebrate RNA viruses is largely limited to those found in mammalian and avian hosts and associated with overt disease. Here, using a large-scale meta-transcriptomic approach, we discover 214 vertebrate-associated viruses in reptiles, amphibians, lungfish, ray-finned fish, cartilaginous fish and jawless fish. The newly discovered viruses appear in every family or genus of RNA virus associated with vertebrate infection, including those containing human pathogens such as influenza virus, the
Arenaviridae
and
Filoviridae
families, and have branching orders that broadly reflected the phylogenetic history of their hosts. We establish a long evolutionary history for most groups of vertebrate RNA virus, and support this by evaluating evolutionary timescales using dated orthologous endogenous virus elements. We also identify new vertebrate-specific RNA viruses and genome architectures, and re-evaluate the evolution of vector-borne RNA viruses. In summary, this study reveals diverse virus–host associations across the entire evolutionary history of the vertebrates.
Around 200 new vertebrate-specific viruses are discovered, and every vertebrate-specific viral family known to infect mammals and birds is also present in amphibians, reptiles or fish, suggesting that evolution of vertebrate viruses mirrors that of vertebrate hosts.
Journal Article
Hagfish from the Cretaceous Tethys Sea and a reconciliation of the morphological–molecular conflict in early vertebrate phylogeny
Hagfish depart so much from other fishes anatomically that they were sometimes considered not fully vertebrate. They may represent: (i) an anatomically primitive outgroup of vertebrates (the morphology-based craniate hypothesis); or (ii) an anatomically degenerate vertebrate lineage sister to lampreys (the molecular-based cyclostome hypothesis). This systematic conundrum has become a prominent case of conflict between morphology- and molecular-based phylogenies. To date, the fossil record has offered few insights to this long-branch problem or the evolutionary history of hagfish in general, because unequivocal fossil members of the group are unknown. Here, we report an unequivocal fossil hagfish from the early Late Cretaceous of Lebanon. The soft tissue anatomy includes key attributes of living hagfish: cartilages of barbels, postcranial position of branchial apparatus, and chemical traces of slime glands. This indicates that the suite of characters unique to living hagfish appeared well before Cretaceous times. This new hagfish prompted a reevaluation of morphological characters for interrelationships among jawless vertebrates. By addressing nonindependence of characters, our phylogenetic analyses recovered hagfish and lampreys in a clade of cyclostomes (congruent with the cyclostome hypothesis) using only morphological data. This new phylogeny places the fossil taxon within the hagfish crown group, and resolved other putative fossil cyclostomes to the stem of either hagfish or lamprey crown groups. These results potentially resolve the morphological–molecular conflict at the base of the Vertebrata. Thus, assessment of character nonindependence may help reconcile morphological and molecular inferences for other major discords in animal phylogeny.
Journal Article
Reconstruction of proto-vertebrate, proto-cyclostome and proto-gnathostome genomes provides new insights into early vertebrate evolution
Ancient polyploidization events have had a lasting impact on vertebrate genome structure, organization and function. Some key questions regarding the number of ancient polyploidization events and their timing in relation to the cyclostome-gnathostome divergence have remained contentious. Here we generate de novo long-read-based chromosome-scale genome assemblies for the Japanese lamprey and elephant shark. Using these and other representative genomes and developing algorithms for the probabilistic macrosynteny model, we reconstruct high-resolution proto-vertebrate, proto-cyclostome and proto-gnathostome genomes. Our reconstructions resolve key questions regarding the early evolutionary history of vertebrates. First, cyclostomes diverged from the lineage leading to gnathostomes after a shared tetraploidization (1R) but before a gnathostome-specific tetraploidization (2R). Second, the cyclostome lineage experienced an additional hexaploidization. Third, 2R in the gnathostome lineage was an allotetraploidization event, and biased gene loss from one of the subgenomes shaped the gnathostome genome by giving rise to remarkably conserved microchromosomes. Thus, our reconstructions reveal the major evolutionary events and offer new insights into the origin and evolution of vertebrate genomes.
Early vertebrate genomes were shaped by multiple whole-genome duplication (WGD) events of debated timings. Here the authors’ reconstruction of ancestral genomes using the probabilistic macrosynteny model supports a WGD shared by all vertebrates and a gnathostome-specific WGD, and reveals evidence of a cyclostome-specific genome triplication.
Journal Article