Genus

About: Genus is a research topic. Over the lifetime, 68921 publications have been published within this topic receiving 590966 citations. The topic is also known as: monospecies genus & genus (zoology).

Molecular Phylogeny of the Plant Pathogenic Genus Botrytis and the Evolution of Host Specificity

Abstract: The cosmopolitan genus Botrytis contains 22 recognized species and one hybrid. The current classification is largely based on morphological characters and, to a minor extent, on physiology and host range. In this study, a classification of the genus was constructed based on DNA sequence data of three nuclear protein-coding genes (RPB2, G3PDH, and HSP60) and compared with the traditional classification. Sexual reproduction and the host range, important fitness traits, were traced in the tree and used for the identification of major evolutionary events during speciation. The phylogenetic analysis corroborated the classical species delineation. In addition, the hybrid status of B. allii (B. byssoidea x B. aclada) was confirmed. Both individual gene trees and combined trees show that the genus Botrytis can be divided into two clades, radiating after the separation of Botrytis from other Sclerotiniaceae genera. Clade 1 contains four species that all colonize exclusively eudicot hosts, whereas clade 2 contains 18 species that are pathogenic on either eudicot (3) or monocot (15) hosts. A comparison of Botrytis and angiosperm phylogenies shows that cospeciation of pathogens and their hosts have not occurred during their respective evolution. Rather, we propose that host shifts have occurred during Botrytis speciation, possibly by the acquisition of novel pathogenicity factors. Loss of sexual reproduction has occurred at least three times and is supposed to be a consequence of negative selection

New classification for the composite genus Aedes (Diptera: Culicidae: Aedini), elevation of subgenus Ochlerotatus to generic rank, reclassification of the other subgenera, and notes on certain subgenera and species.

Abstract: The composite genus Aedes is divided into 2 genera, Aedes and Ochlerotatus, on the basis of consistent primary characters of the female and male genitalia. Ochlerotatus is separated into 2 sections. Additional supplemental features of the female and male genitalia, 4th-stage larvae, and pupae are provided for the separation of the genera and sections as well as a discussion of exceptions and comparisons. This classification is based on a morphological examination of specimens of over 65% of the currently recognized species and all subgenera previously included in Aedes and representative material of all subgenera and genera of tribe Aedini. Published literature was examined and evaluated. All currently recognized subgenera are assigned to the appropriate genus. The proposed new generic classification provides better defined genera and a more natural arrangement of included taxa. Armigerini is formally recognized as a synonym, in part, of Aedini.

Phylogenomics and systematics in Pseudomonas

Abstract: The genus Pseudomonas currently contains 144 species, making it the genus of Gram-negative bacteria that contains the largest number of species. Currently, multilocus sequence analysis (MLSA) is the preferred method for establishing the phylogeny between species and genera. Four partial gene sequences of housekeeping genes (16S rRNA, gyrB, rpoB, and rpoD) were obtained from 112 complete or draft genomes of strains related to the genus Pseudomonas that were available in databases. These genes were analyzed together with the corresponding sequences of 133 Pseudomonas type strains of validly published species to assess their correct phylogenetic assignations. We confirmed that 30% of the sequenced genomes of non-type strains were not correctly assigned at the species level in the accepted taxonomy of the genus and that 20% of the strains were not identified at the species level. Most of these strains had been isolated and classified several years ago, and their taxonomic status has not been updated by modern techniques. MLSA was also compared with indices based on the analysis of whole-genome sequences that have been proposed for species delineation, such as tetranucleotide usage patterns (TETRA), average nucleotide identity (ANIm, based on MUMmer and ANIb, based on BLAST) and genome-to-genome distance (GGDC). TETRA was useful for discriminating Pseudomonas from other genera, whereas ANIb and GGDC clearly separated strains of different species. ANIb showed the strongest correlation with MLSA. The correct species classification is a prerequisite for most diversity and evolutionary studies. This work highlights the necessity for complete genomic sequences of type strains to build a phylogenomic taxonomy and that all new genome sequences submitted to databases should be correctly assigned to species to avoid taxonomic inconsistencies.