Indeed, homoploid speciation (hybrid speciation without a change in chromosome number) has been evidenced for some fungal species (such as the basidiomycota Microbotryum violaceum). As for plants and animals, fungal hybrids and polyploids display structural and functional modifications compared to their progenitors and diploid counterparts. In particular, the structural and functional outcomes of polyploid Saccharomyces genomes strikingly reflect the evolutionary fate of plant polyploid ones. Large chromosomal rearrangements leading to chimeric chromosomes have been described, as well as more punctual genetic modifications such as gene loss. The homoealleles of the allotetraploid yeast S. pastorianus show unequal contribution to the transcriptome. Phenotypic diversification is also observed following polyploidization and/or hybridization in fungi, producing the fuel for natural selection and subsequent adaptation and speciation. Chromalveolata
Other eukaryotic taxa have experienced one or more polyploidization events during their evolutionary history (see Albertin and Marullo, 2012 for review). The oomycetes, which are non-true fungi members, contain several examples of paleopolyploid and polyploid species, such as within the genus Phytophthora. Some species of brown algae (Fucales, Laminariales and diatoms) contain apparent polyploid genomes. In the Alveolata group, the remarkable species Paramecium tetraurelia underwent three successive rounds of whole-genome duplication and established itself as a major model for paleopolyploid studies. Bacteria
Each Deinococcus radiodurans bacterium contains 4-8 copies of its chromosome. Exposure of D. radiodurans to X-ray irradiation or desiccation can shatter its genomes into hundred of short random fragments. Nevertheless, D. radiodurans is highly resistant to such exposures.
The letter x is used to represent the number of chromosomes in a single set:
haploid (one set; 1x)
diploid (two sets; 2x)
triploid (three sets; 3x), for example sterile saffron crocus, or seedless watermelons, also common in the phylum Tardigrada
tetraploid (four sets; 4x), for example Salmonidae fish, the cotton Gossypium hirsutum
pentaploid (five sets; 5x), for example Kenai Birch (Betula kenaica)
hexaploid (six sets; 6x), for example some species of wheat, kiwifruit
heptaploid or septaploid (seven sets; 7x)
octaploid or octoploid, (eight sets; 8x), for example Acipenser (genus of sturgeon fish), dahlias
decaploid (ten sets; 10x), for example certain strawberries
dodecaploid or duodecaploid (twelve sets; 12x), for example the plants Celosia argentea and Spartina anglica  or the amphibian Xenopus ruwenzoriensis. Classification
Autopolyploidy
Autopolyploids are polyploids with multiple chromosome sets derived from a single taxon. Two examples of natural autopolyploids are the piggyback plant, Tolmiea menzisii and the white sturgeon, Acipenser transmontanum. Most instances of autopolyploidy result from the fusion of unreduced (2n) gametes, which results in either triploid (n + 2n = 3n) or tetraploid (2n + 2n = 4n) offspring. Triploid offspring are typically sterile (as in the phenomenon of triploid block), but in some cases they may produce high proportions of unreduced gametes and thus aid the formation of tetraploids. This pathway to tetraploidy is referred to as the triploid bridge. Triploids may also persist through asexual reproduction. In fact, stable autotriploidy in plants is often associated with apomictic mating systems. In agricultural systems, autotriploidy can result in seedlessness, as in watermelons and bananas.