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Most species whose cells have nuclei are diploid, meaning they have two complete sets of chromosomes, one from each of two parents; each set contains the same number of chromosomes, and the chromosomes are joined in pairs of homologous chromosomes. However, some organisms are polyploid. Polyploidy is especially common in plants.
Polyploid speciation is commonly observed in plants because their nature allows them to support genome duplications. Polyploids are considered a new species because the occurrence of a whole genome duplication imposes post-zygotic barriers, which enable reproductive isolation between parent populations and hybrid offspring.
The list of organisms by chromosome count describes ploidy or numbers of chromosomes in the cells of various plants, animals, protists, and other living organisms.This number, along with the visual appearance of the chromosome, is known as the karyotype, [1] [2] [3] and can be found by looking at the chromosomes through a microscope.
It has been suggested that many of the existing plant and most animal species have undergone an event of polyploidization in their evolutionary history. [77] [78] Reproduction of successful polyploid species is sometimes asexual, by parthenogenesis or apomixis, as for unknown reasons many asexual organisms are polyploid. Rare instances of ...
Virtually all sexually reproducing organisms are made up of somatic cells that are diploid or greater, but ploidy level may vary widely between different organisms, between different tissues within the same organism, and at different stages in an organism's life cycle. Half of all known plant genera contain polyploid species, and about two ...
In plants, hybridization mostly generates speciation events, [5] and commonly produces polyploid species. Factors like polyploidy events also plays significant factors for understanding the hybridization events (Example: an F1 hybrid of Jatropha curcas x Ricinus communis), [6] because these polyploids tend to have an advantage for the early ...
Polyploid speciation, which involves changes in chromosome number, is a more common phenomenon, especially in plant species. Polyploidy is a mechanism that has caused many rapid speciation events in sympatry because offspring of, for example, tetraploid x diploid matings often result in triploid sterile progeny. [257]
Polyploidy is pervasive in plants and some estimates suggest that 30–80% of living plant species are polyploid, and many lineages show evidence of ancient polyploidy (paleopolyploidy) in their genomes. [8] [9] [10] Huge explosions in angiosperm species diversity appear to have coincided with ancient genome duplications shared by many species.