This revision of the classification of unicellular eukaryotes updates that of Levine et al. (1980) for the protozoa and expands it to include other protists. Whereas the previous revision was primarily to incorporate the results of ultrastructural studies, this revision incorporates results from both ultrastructural research since 1980 and molecular phylogenetic studies. We propose a scheme that is based on nameless ranked systematics. The vocabulary of the taxonomy is updated, particularly to clarify the naming of groups that have been repositioned. We recognize six clusters of eukaryotes that may represent the basic groupings similar to traditional ''kingdoms.'' The multicellular lineages emerged from within monophyletic protist lineages: animals and fungi from Opisthokonta, plants from Archaeplastida, and brown algae from Stramenopiles.

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The new higher level classification of eukaryotes with emphasis on the taxonomy of protists

A mechanism for gene conversion is proposed which overcomes many of the difficulties that any copy choice model encounters. It is suggested that along with general genetic pairing of homologous genomes at meiosis, effective pairing over short regions of the genetic material occurs at the molecular level by the separation of the strands of the DNA double helices, followed by the annealing of strands from two homologous chromatids. If the annealed region happens to span a heterozygous site, mispairing of bases will occur. Such a situation may be analogous to that in DNA which is damaged by mutagens; the same or similar repair mechanisms may operate, and these, by adjusting the base sequences in order to restore normal base pairing, would bring about gene conversion in the absence of any genetic replication. The model indicates how precise breakage and rejoining of chromatids could occur in the vicinity of the conversion, so that conversion would frequently be accompanied by the recombination of outside markers. The model also proposes that the distance between two mutant sites on a fine structure map depends not so much on the frequency of a recombinational event occurring between them, but rather on the degree of inhibition of the processes of genetic pairing by the mutants themselves. The model will explain almost all the data in a formal way, and it has the advantage over copy choice mechanisms for gene conversion in (1) being compatible with semi-conservative replication of DNA, (2) not invoking DNA synthesis during or after genetic pairing, (3) providing a molecular mechanism for close specific pairing, (4) making it unnecessary to postulate sister strand exchange or a process akin to this, (5) suggesting why rates of gene conversion in opposite directions are sometimes unequal and (6) providing an explanation of the clustering of mutant sites, a basis for map expansion and for the apparently capricious departure of fine structure maps from additivity. Although the model proposed is a general rather than a specific one, it suggests that the process of conversion and intragenic recombination is more complex than is usually believed, since it depends on several interacting factors. Nevertheless, it is hoped that the introduction of a model with this complexity will help to stimulate specific experiments, and that these will provide definitive information which would never be obtained if simpler models of conversion and intragenic recombination were believed to explain the genetic data sufficiently well.

/pdf/a-mechanism-for-gene-conversion-in-fungi-1tp9iv58rz.pdf

A mechanism for gene conversion in fungi.

The subkingdom Protozoa now inclues over 65,000 named species, of which over half are fossil and approximately 10,000 are parasitic. Among living species, this includes approximately 250 parasitic and 11,300 free-living sarcodines (of which approximately 4,600 are foraminiferids); approximately 1,8000 parasitic and 5,100 free-living flagellates; approximately 5,600 parasitic "Sporozoa" (including Apicomplexa, Microspora, Myxospora, and Ascetospora); and approximately 2,5000 parasitic and 4,700 free-living ciliates. There are undoubtedly thousands more still unnamed. Seven phyla of PROTOZOA are accepted in this classification--SARCOMASTIGOPHORA, LABYRINTHOMORPHA, APICOMPLEXA, MICROSPORA, ASCETOSPORA, MYXOSPORA, and CILIOPHORA. Diagnoses are given for these and for all higher taxa through suborders, and reporesentative genera of each are named. The present scheme is a considerable revision of the Society's 1964 classification, which was prepared at a time when perhaps 48,000 species had been named. It has been necessitated by the acquisition of a great deal of nex taxonomic information, much of it through electron microscopy. It is hoped that the present classification incorporatesmost of the major changes that will be made for some time, and that it will be used for many years by both protozoologist and non-protozoologists.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1550-7408.1980.tb04228.x

A Newly Revised Classification of the Protozoa

are those who consider questions in science which have no unequivocal , experimentally determined answer scarcely worth discussing. Such feeling, along with conservatism, may have been responsible for the long and almost unchallenged dominance of the system of two kingdoms-plants and animals-in the broad classification of organisms. The unchallenged position of these kingdoms has ended, however; alternative systems are being widely considered (1-18) and are appearing in many introductory biology texts (19-24). My purpose in this article is to discuss the merits of two classifications which depart from the traditional two kingdoms, the systems of Copeland (1-3) and Whittaker (4, 5). Two-Kingdom System Man is terrestrial, and he sees around him two major groups of organisms of very different adaptation to nutrition on land-the photosynthetic, rooted, higher plants, and the food-ingesting, motile, higher animals. So distinct in way of life, direction of evolution, and kind of body organization are these groups that a concept of dichotomy-plants versus animals-is almost inescapable if they are considered by themselves. The two groups became the nuclei around which concepts of the plant and animal kingdoms were developed by early naturalists. The kingdoms have been part of the formal classification of living things since Linnaeus (25). Mosses, liverworts, and macroscopic algae are clearly plants in their photo-synthetic and nonmotile way of life, and (though the photosynthetic process itself was not understood by early naturalists) these forms were grouped 150 with the higher land plants. The higher fungi on land are nonmotile, and their apparently \"rooted\" manner of growth suggested the plants. It thus seemed reasonable to assign fungi to the plant kingdom, and some students believed that they had evolved from algae. The wealth of unicellular life discovered by microscopists offered greater difficulty. Some forms were motile and ingested food, however, and were naturally regarded as one-celled animals or proto-zoans. Others were nonmotile and photosynthetic, hence one-celled plants. There remained a wide range of uni-cellular forms in which nonmotility and flagellate or pseudopodial motility, and ingestive, photosynthetic, and absorp-tive nutrition, were combined in various ways which were neither clearly plant-like nor animal-like. In a number of cases plant-like and animal-like unicells were connected by a series of closely related intergrading forms within the same major taxon. There remained also the bacteria which, though few are pho-tosynthetic and many are motile, seemed better treated as plants because of their walled cells. The plant and animal kingdoms …

https://science.sciencemag.org/content/sci/163/3863/150.full.pdf

New concepts of kingdoms of organisms

Colletotrichum - current status and future directions.

A simple new mycetozoan with ballistospores

A number of isolates of the cellular slime mold, Acrasis rosea, differed from each other in the range of microorganisms on which they could grow and fruit. In a test for the possible occurrence of sexual reproduction and genetic recombination, two of the most widely divergent of these physiological races were studied further. Mixed colonies were obtained in agar plate cultures of Rhodotorula mucilaginosa, a yeast utilized by both. When spores from mature fruiting bodies or amoebae migrating out from the mixed colonies were isolated singly, regrown on Rhodotorula, and tested on a critical spectrum of food microorganisms, about 3-4% proved to be distinct from the original two strains. Although some of these new types remained stable for several transfers, they eventually reverted to one or both of the parental types. The possibilities of explaining the neotypes on the basis of diploidy, heterokaryosis, or mixed cytoplasmic effects are discussed. The occurrence of cell anastomoses and occasional binucleate cells favors the latter two possibilities.

Variation in the Cellular Slime Mold Acrasis rosea

Cavostelium bisporum, the second species of the genus to be described, has stalked sporocarps that are consistently 2-spored. The feeding stage varies from uninucleate amoeboid cells to multinuclea...

A New Two-Spored Species of Cavostelium (Protostelida)

(1957). Tulasnellaceae of Tahiti. A Revision of the Family. Mycologia: Vol. 49, No. 5, pp. 663-679.

Tulasnellaceae of Tahiti. A Revision of the Family

This unusual organism was first encountered in the West Indies in December of 1960, during a search for cellular slime molds. Since then, it has appeared in many isolation plates of collections from around the world in tropical and subtropical areas. While it was first thought to be a new species of Protostelium (Olive, 1962), a primitive relative of the cellular slime molds, such an alliance proved incompatible with the discovery that the amoeboid cells develop flagella when placed in water. The fructifications, like those of Protostelium, are quite simple and typically consist of one or two spores on a short stalk. The organism does not fit well into any known group of mycetozoans, and a new genus and family are hereby described to accommodate it.

Lindsay S. Olive

Papers

A simple new mycetozoan with ballistospores

Variation in the Cellular Slime Mold Acrasis rosea

A New Two-Spored Species of Cavostelium (Protostelida)

Tulasnellaceae of Tahiti. A Revision of the Family

A new member of the mycetozoa