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.

New or noteworthy species of Tremellales from the southern Appalachians-III

Three new species of Protostelium (Order Protostelida of the Mycetozoa) are described: P. irregularis, P. zonatum, and P. pyriformis, all with rather wide distribution and occurring on dead attached plant parts, less often in soil and humus. The latter two species differ from the first and from the other two known species, P. mycophaga Olive and Stoianovitch and P. arachisporum Olive, in the endogenous origin of the stalk. P. mycophaga var. crassipes, with vesicular stalk bases, is the third variety of that species to be described. A key to the genus is included. PROTOSTELIUM Olive and Stoianovitch (1960) is the type genus of the family Protostelidae, order Protostelida of the Mycetozoa (Olive and Stoianovitch, 1966a). Up to the present time it contains only two valid species, P. mycophaga Olive and Stoianovitch (1960) and P. arachisporum Olive (1962). In the present paper three new species and one new variety are described and additional developmental details on members of the genus are presented. Protostelium is characterized chiefly by its predominantly uninucleate, non-flagellate, phagotrophic, amoeboid cells and slender-stalked sporocarps that bear the deciduous spores singly. N\Jembers of the genus occur primarily on dead plant parts (pods, capsules, berries, flowers, etc.) that have remained attached to the plants, though some species are occasionally found in soil, humus, or rotting wood. The trophic stage ingests such foods as yeasts, fungal spores and bacteria. Methods for isolating and culturing protostelids in the laboratory have been described in an earlier publication (Olive, 1967), as have the photographic techniques used in the present research. While uninucleate amoebae and spores are characteristic of the group, plurinucleate cells or even aplanate multinucleate protoplasts appear in cultures of some species. The multinucleate ones, however, do not develop into the extensive reticulate plasmodia that characterize such genera as Schizoplasmodium and Schizoplasmodiopsis (Olive, 1967). Cell division is by binary fission, following which the nucleolar material reappears in each daughter nucleus as several separate bodies that eventually fuse into a single larger nucleolus more or less centrally positioned in the nucleus. It is common to find considerable range in cell and nuclear size within an isolate, which may indicate a range in ploidy, but there are no cytological data to substantiate the latter. I Received for publication 17 March 1969. This research was supported by grants GB-5508, GB7392, and GB-501 from the National Science Foundation. No evidence of sexuality has been observed. Typical sporulating cultures are regenerated from single spores. Plurinucleate protoplasts appear to arise by cell anastomosis as well as by nuclear division without cytokinesis. Such protoplasts may divide into smaller ones by plasmotomy. The amoebae commonly produce filose pseudopodia, especially when placed in water. However, under certain conditions, such as prolonged flattening between a cover slip and a thin agar layer ("sandwich" preparation), they frequently produce lobose pseudopodia instead. Ontogeny of the protostelid sporocarp has been described elsewhere (Olive and Stoianovitch, 1966a) and, with the exception of the two new species with bell-shaped or pyriform spores, is applicable to the genus Protostelium. The stalk-generating part of the culminating protoplast is typically hemispherical, with a narrow extension passing into the upper part of the eveloping stalk, but in the two exceptional species the steliogen is cylindric and the stalk of endogenous origin. The mature sporocarp typically consists of a narrow stalk tube terminated by a single spore, the whole being enveloped by a thin, closely applied sheath. At least one species does not have a demonstrable stalk tube. All species are characterized by having deciduous spores, though in some the spores fall off more readily than in others. The manner in which the spore separates from the stalk tip is not well understood. A key to the species and varieties of the genus is presented below. KEY TO THE GENUS PROTOSTELIUM Spores globose to subglobose Protoplasts orange-pigmented; spores averaging less than 15,g diam; microcysts fairly regular in outline .... . mycophaga Stalk with conspicuous vesicular enlargement at base .... var. crassipes Stalk without conspicuous basal enlargement

Monograph of the genus protostelium

The Lower Basidiomycetes of Tahiti-I.

IN JUNE of 1956, while engaged in a study of the fungi of the Society Islands, the writer found an unusual basidiomycete in a wooded area near his residence in the Punaauia District of Tahiti. The fungus appeared as a thin, gray, waxy-pruinose growth on the bark of a dead limb of the mango tree. A microscopic examination revealed basidia with four long, stout sterigmata typical of the genus Ceratobasidium. Furthermore, the basidiospores, like those of the latter genus, were found germinating by repetition. On the other hand, the new fungus differs markedly from all known species of Ceratobasidium in having gloeoeystidia and incompletely septate basidia. If the basidium is viewed apically after the septa have appeared, the cruciform arrangement of the septa, so characteristic of the tremellaceous basidium, may be observed, and the basidium appears to be 4-celled (fig. 8). But when the basidium is viewed laterally the septa are found to be incomplete below. -Occasionally a septum seems to extend all the way through the basidium or nearly so, but a change of focus always shows it to be interrupted in some area (fig. 5, 6). The septa usually begin to appear just before the sterigmata start developing (fig. 2). They may persist during spore formation (fig. 10, 13, 14) but frequently may not be detected at this time (fig. 11, 12, 15, 16), and it is probable that in a majority of the basidia they disintegrate by the time of spore discharge. Possibly they do not appear at all in some basidia. To the writer's knowledge no such fungus has been previously reported. It is hereby described as a new species, and a new generic name is proposed for it. The new genus is believed to occupy a position of primitiveness in the Ceratobasidiaceae, indicating a phylogenetic connetcion of this family with the Tremellaceae.

Lindsay S. Olive

Papers

New or noteworthy species of Tremellales from the southern Appalachians-III

Monograph of the genus protostelium

The Lower Basidiomycetes of Tahiti-I.

Two new genera of the ceratobasidiaceae and their phylogenetic significance

The genus protostelium