An evolutionary radiation is an increase in taxonomic diversity that is caused by elevated rates of speciation , that may or may not be associated with an increase in morphological disparity. A significantly large and diverse radiation within a relatively short geologic time scale (e.g. a period or epoch ) is often referred to as an explosion . Radiations may affect one clade or many, and be rapid or gradual; where they are rapid, and driven by a single lineage's adaptation to their environment, they are termed adaptive radiations .
19-595: The candidate phyla radiation (also referred to as CPR group ) is a large evolutionary radiation of bacterial lineages whose members are mostly uncultivated and only known from metagenomics and single cell sequencing . They have been described as nanobacteria (not to be confused with non-living nanoparticles of the same name ) or ultra-small bacteria due to their reduced size (nanometric) compared to other bacteria. Originally (circa 2016), it has been suggested that CPR represents over 15% of all bacterial diversity and may consist of more than 70 different phyla. However,
38-417: A clade's speciation rate coupled with divergence of morphological features that are directly related to ecological habits; these radiations involve speciation not driven by geographic factors and occurring in sympatry; they also may be associated with the acquisition of a key trait. Nonadaptive radiations arguably encompass every type of evolutionary radiation that is not an adaptive radiation, although when
57-421: A more precise mechanism is known to drive diversity, it can be useful to refer to the pattern as, e.g., a geographic radiation. Geographic radiations involve an increase in speciation caused by increasing opportunities for geographic isolation. Radiations may be discordant, with either diversity or disparity increasing almost independently of the other, or concordant, where both increase at a similar rate. Where
76-486: A series of extinctions from which they repeatedly re-diversified; and trilobites which, during the Cambrian, rapidly evolved into a variety of forms occupying many of the niches exploited by crustaceans today. A number of groups have undergone evolutionary radiation in relatively recent times. The cichlids in particular have been much studied by biologists . In places such as Lake Malawi they have evolved into
95-657: A superphylum called Patescibacteria which encompassed several phyla later attributed to the CPR group. Therefore, Patescibacteria and CPR are often used as synonyms. The former name is not necessarily obsolete: for example, the GTDB uses this name because they consider the CPR group a phylum. Although there are a few exceptions, members of the candidate phyla radiation generally lack several biosynthetic pathways for several amino acids and nucleotides. To date, there has been no genomic evidence that indicates that they are capable of producing
114-445: A very wide variety of forms, including species that are filter feeders, snail eaters, brood parasites, algal grazers, and fish-eaters. Caribbean anoline lizards are another well-known example of an adaptive radiation. Grasses have been a success, evolving in parallel with grazing herbivores such as horses and antelope . Armatimonadota Armatimonadota is a phylum of gram-negative bacteria . Armatimonadota
133-415: Is more closely related to Chloroflexota . The evolutionary relationships that are typically supported by these studies are as follows. Gracilicutes DST Cyanobacteria/Melainabacteria Bacillota and Mycoplasmatota Actinomycetota Armatimonadota Eremiobacteraeota CPR Dormibacteraeota Chloroflexota Because many CPR members are uncultivable, they cannot be formally put into
152-1021: The Avalon Explosion , the Cambrian Explosion , the Great Ordovician Biodiversification Event , the Carboniferous-Earliest Permian Biodiversification Event , the Mesozoic–Cenozoic Radiation , the radiation of land plants after their colonisation of land , the Cretaceous radiation of angiosperms , and the diversification of insects, a radiation that has continued almost unabated since the Devonian , 400 million years ago . Adaptive radiations involve an increase in
171-509: The Genome Taxonomy Database (2018) based on relative evolutionary divergence found that CPR represents a single phylum, with earlier figures inflated by the rapid evolution of ribosomal proteins. CPR lineages are generally characterized as having small genomes and lacking several biosynthetic pathways and ribosomal proteins. This has led to the speculation that they are likely obligate symbionts . Earlier work proposed
190-456: The L30 ribosomal protein , a trait that is often seen in symbionts. Many of its characteristics are similar or analogous to those of ultra-small archaea ( DPANN ). The Candidate phyla radiation was found to be the most basal-branching lineage in bacteria according to some early phylogenetic analyses of this group based on ribosomal proteins and protein family occurrence profiles. These studies found
209-728: The bacterial taxonomy , but a number of provisional, or Candidatus , names have been generally agreed on. As of 2017, two superphyla are generally recognized under CPR, Parcubacteria and Microgenomates. The Phyla under CPR include: " Wirthbacteria " " Dojkabacteria " " Katanobacteria " " Microgenomatia " " Absconditabacteria " " Gracilibacteria " " Berkelbacteria " (UBA1384) " Kazanbacteria " (Kazan) " Howlettbacteria " " Saccharimonadia " " Andersenbacteria " " Doudnabacteria " " Torokbacteria " (GCA-2792135) ABY1 " Paceibacteria " "Woykebacterales" (CG2-30-54-11) "Curtissbacterales" "Daviesbacterales" "Roizmanbacterales" (UBA1406) Evolutionary radiation Perhaps
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#1732801913502228-807: The Early Cambrian , Early Ordovician , to a lesser degree throughout the Silurian and Devonian , and then again during the Carboniferous and earliest Permian . During these periods, different species of brachiopods independently assumed a similar morphology, and presumably mode of life, to species that had lived millions of years before. This phenomenon, known as homeomorphy, is explained by convergent evolution : when subjected to similar selective pressures, organisms will often evolve similar adaptations. Further examples of rapid evolutionary radiation can be observed among ammonites , which suffered
247-402: The following phylogeny between phyla and superphyla. The superphyla are shown in bold. The other bacteria Wirthbacteria Dojkabacteria Katanobacteria Microgenomates Berkelbacteria Saccharibacteria Peregrinibacteria Absconditabacteria Gracilibacteria Parcubacteria However, several recent studies have suggested that the CPR belongs to Terrabacteria and
266-406: The lipids essential for cell envelope formation. Additionally, they tend to lack complete TCA cycles and electron transport chain complexes, including ATP synthase. This lack of several important pathways found in most free-living prokaryotes indicates that the candidate phyla radiation is composed of obligate fermentative symbionts. Furthermore, CPR members have unique ribosomal features. While
285-540: The mechanism of diversification is ambiguous and the species seem to be closely related, sometimes the terms "species radiation," "species flock" or " species complex " are used. Much of the work carried out by palaeontologists studying evolutionary radiations has been using marine invertebrate fossils simply because these tend to be much more numerous and easy to collect in quantity than large land vertebrates such as mammals or dinosaurs . Brachiopods , for example, underwent major bursts of evolutionary radiation in
304-481: The members of CPR are generally uncultivable, and therefore missed in culture-dependent methods, they are also often missed in culture-independent studies that rely on 16S rRNA sequences. Their rRNA genes appear to encode proteins and have self-splicing introns , features that are rarely seen in bacteria, although they have previously been reported. Owing to these introns, members of CPR are not detected in 16S-dependent methods. Additionally, all CPR members are missing
323-598: The most familiar example of an evolutionary radiation is that of placental mammals immediately after the extinction of the non-avian dinosaurs at the end of the Cretaceous , about 66 million years ago. At that time, the placental mammals were mostly small, insect-eating animals similar in size and shape to modern shrews . By the Eocene (58–37 million years ago), they had evolved into such diverse forms as bats , whales , and horses . Other familiar radiations include
342-857: Was isolated from rhizoplane of an aquatic plant (a reed, Phragmites australis ) inhabiting a freshwater lake in Japan. Chthonomonas calidirosea , an aerobic, saccharolytic , obligately thermophilic, motile, non-spore-forming bacterium, strain T49(T), was isolated from geothermally heated soil at Hell's Gate, Tikitere, New Zealand. Chthonomonas calidirosea Fimbriimonas ginsengisoli Armatimonas rosea Capsulimonas corticalis Abditibacterium utsteinense " Ca. Fervidibacter sacchari " " Ca. Hippobium faecium " Fimbriimonas ginsengisoli " Ca. Nitrosymbiomonas proteolytica " Chthonomonas calidirosea Armatimonas rosea Capsulimonas corticalis The currently accepted taxonomy
361-490: Was originally described solely on the basis of environmental 16S rRNA gene clone sequences, and was temporarily titled candidate phylum OP10. However, in 2011 a bacterial strain belonging to the phylum was isolated from an aquatic plant in Japan. The species was named Armatimonas rosea and was the first member of its phylum, genus, and species. Armatimonas rosea , an aerobic chemoheterotrophic bacterium, strain YO-36T,
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