Editing Ploidy (section)

== Adaptive and ecological significance of variation in ploidy ==
There is continued study and debate regarding the fitness advantages or disadvantages conferred by different ploidy levels. A study comparing the [[karyotypes]] of endangered or invasive plants with those of their relatives found that being polyploid as opposed to diploid is associated with a 14% lower risk of being endangered, and a 20% greater chance of being invasive.<ref name="Pandit-2011">{{Cite journal | last=Pandit | first=M. K. |author2=Pocock, M. J. O. |author3=Kunin, W. E. | title=Ploidy influences rarity and invasiveness in plants | journal=[[Journal of Ecology]] | volume=99 | issue= 5| pages=1108–1115 | date=2011-03-28 |  doi=10.1111/j.1365-2745.2011.01838.x | s2cid=38197332 | doi-access=free | bibcode=2011JEcol..99.1108P }}</ref> Polyploidy may be associated with increased vigor and adaptability.<ref name="Gilbert-2011">{{cite journal | last=Gilbert | first=Natasha | title=Ecologists find genomic clues to invasive and endangered plants | journal=Nature | date=2011-04-06 | url=http://www.nature.com/news/2011/110406/full/news.2011.213.html#B1 | doi=10.1038/news.2011.213 | access-date=2011-04-07 }}</ref> Some studies suggest that selection is more likely to favor diploidy in host species and haploidy in parasite species.<ref>{{cite journal |author1=Nuismer S. |author2=Otto S.P. | year=2004 | title=Host-parasite interactions and the evolution of ploidy | journal=Proc. Natl. Acad. Sci. USA | volume=101 | issue=30 | pages=11036–11039 | doi=10.1073/pnas.0403151101|pmid=15252199 | pmc=503737 | bibcode=2004PNAS..10111036N |doi-access=free }}</ref> However, polyploidization is associated with an increase in [[transposable element]] content<ref>{{Cite journal |last=McClintock |first=B. |date=1984-11-16 |title=The significance of responses of the genome to challenge |url=https://pubmed.ncbi.nlm.nih.gov/15739260/ |journal=Science |volume=226 |issue=4676 |pages=792–801 |doi=10.1126/science.15739260 |issn=0036-8075 |pmid=15739260|bibcode=1984Sci...226..792M }}</ref><ref>{{Cite journal |last1=Matzke |first1=M.A |last2=Matzke |first2=A.J.M |date=June 1998 |title=Polyploidy and transposons |url=https://doi.org/10.1016/S0169-5347(98)01390-1 |journal=Trends in Ecology & Evolution |volume=13 |issue=6 |pages=241 |doi=10.1016/s0169-5347(98)01390-1 |pmid=21238281 |bibcode=1998TEcoE..13R.241M |issn=0169-5347}}</ref> and relaxed [[purifying selection]] on [[recessive]] deleterious alleles.<ref>{{Cite journal |last=Ronfort |first=J. |date=August 1999 |title=The mutation load under tetrasomic inheritance and its consequences for the evolution of the selfing rate in autotetraploid species |journal=Genetics Research |language=en |volume=74 |issue=1 |pages=31–42 |doi=10.1017/S0016672399003845 |issn=1469-5073|doi-access=free }}</ref><ref>{{Cite journal |last1=Baduel |first1=Pierre |last2=Quadrana |first2=Leandro |last3=Hunter |first3=Ben |last4=Bomblies |first4=Kirsten |last5=Colot |first5=Vincent |date=2019-12-20 |title=Relaxed purifying selection in autopolyploids drives transposable element over-accumulation which provides variants for local adaptation |journal=Nature Communications |language=en |volume=10 |issue=1 |pages=5818 |doi=10.1038/s41467-019-13730-0 |pmid=31862875 |bibcode=2019NatCo..10.5818B |s2cid=209420359 |issn=2041-1723|doi-access=free |pmc=6925279 }}</ref>

When a germ cell with an uneven number of chromosomes undergoes meiosis, the chromosomes cannot be evenly divided between the daughter cells, resulting in [[aneuploid]] gametes. Triploid organisms, for instance, are usually sterile. Because of this, triploidy is commonly exploited in agriculture to produce seedless fruit such as bananas and watermelons. If the fertilization of human gametes results in three sets of chromosomes, the condition is called [[triploid syndrome]].{{citation needed|date=May 2023}}

In [[unicellular organism]]s the [[ploidy nutrient limitation hypothesis]] suggests that [[nutrient limitation]] should encourage haploidy in preference to higher ploidies. This hypothesis is due to the higher [[surface-to-volume ratio]] of haploids, which eases nutrient uptake, thereby increasing the internal nutrient-to-demand ratio. Mable 2001 finds ''[[Saccharomyces cerevisiae]]'' to be somewhat inconsistent with this hypothesis however, as haploid growth is faster than diploid under high nutrient conditions. The NLH is also tested in haploid, diploid, and polyploid fungi by Gerstein et al. 2017. This result is also more complex: On the one hand, under [[phosphorus]] and other nutrient limitation, lower ploidy is selected as expected. However under normal nutrient levels or under limitation of only [[nitrogen]], higher ploidy was selected. Thus the NLH {{endash}} and more generally, the idea that haploidy is selected by harsher conditions {{endash}} is cast into doubt by these results.<ref name="Blischak-2018">{{cite journal | last1=Blischak | first1=Paul D. | last2=Mabry | first2=Makenzie E. | last3=Conant | first3=Gavin C. | last4=Pires | first4=J. Chris | title=Integrating Networks, Phylogenomics, and Population Genomics for the Study of Polyploidy | journal=[[Annual Review of Ecology, Evolution, and Systematics]] | publisher=[[Annual Reviews (publisher)|Annual Reviews]] | volume=49 | issue=1 | date=2018-11-02 | issn=1543-592X | doi=10.1146/annurev-ecolsys-121415-032302 | pages=253–278| s2cid=92205236 | doi-access=free }}</ref>

Older WGDs have also been investigated. Only as recently as 2015 was the ancient [[whole genome duplication]] in [[Baker's yeast]] proven to be [[allopolyploid]], by Marcet-Houben and Gabaldón 2015. It still remains to be explained why there are not more polyploid events in fungi, and the place of [[neopolyploidy]] and [[mesopolyploidy]] in [[evolution of fungi|fungal history]].<ref name="Blischak-2018" />