Is lack of cycad (Cycadales) diversity a result of a lack of polyploidy?

Gorelick, Root; Olson, Krystle

doi:10.1111/j.1095-8339.2010.01103.x

Cited by 27 publications

(24 citation statements)

References 127 publications

(143 reference statements)

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“…We showed that only by looking at the genome level can the functions and origins of sex be understood (Gorelick and Heng, ). We also showed that radiations in plants may largely be a result of polyploidy, aka whole genome duplication, which (antithetically, as we show below) is definitely a genetic rather than a genomic phenomenon (Gorelick and Olson, ).…”

supporting

confidence: 57%

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Polyploidy Is Genetic Hence May Cause Non‐Adaptive Radiations, Whereas Pseudopolyploidy Is Genomic Hence May Cause Adaptive Non‐Radiations

Gorelick

Olson

2013

J Exp Zool Pt B

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There are two ways eukaryotes double number of chromosomes: (1) whole genome duplication (polyploidy), in which all nuclear DNA is replicated, and (2) karyotypic fission (pseudopolyploidy), in which all chromosomes are physically bifurcated. We contrast polyploidy with pseudopolyploidy, highlighting when it is crucial to look at genetic vs. genomic levels. We review history of pseudopolyploidy, including recent mechanisms by which chromosomal bifurcation may occur and outline methods for detecting such genomic changes. We then delve into the evolutionary implications, with particular focus on adaptive potential, of these two forms of doubling chromosome numbers. We address the common assertion that polyploidy induces adaptive radiations, which contains three fallacies. First, while polyploidy causes quantum speciation, evolutionary theory implies that these radiations should be non-adaptive. Polyploidy causes reproductive isolation, minute effective population sizes, and increased mutation rates, which all imply a diminished role for selection. Second, due to lack of karyotyping in recent decades and lack of distinction between genomic and genetic effects, it is usually impossible to detect pseudopolyploids. Third, pseudopolyploids lack minority cytotype exclusion because they readily backcross with their progenitors, which thereby means no reproductive isolation for newly formed pseudopolyploids. Pseudopolyploidy will thereby not result in radiations until pseudopolyploid descendants undergo subsequent chromosome rearrangements or grow new centromeres. Pseudopolyploids may have a modest selective advantage over their progenitors due to diminished linkage disequilibrium. Thus, pseudopolyploidy may induce adaptive non-radiations. We encourage a renaissance of karyotyping to distinguish between these two mechanisms and a renaissance in genomic perspectives in evolution.

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supporting

confidence: 57%

“…This not a scenario in which adaptation would ever be expected (Lynch, , ). For further discussion of how polyploidy probably causes radiations that are not adaptive see Gorelick () and Gorelick and Olson ().…”

Section: Polyploidy Causes Radiations But Is Not Adaptivementioning

confidence: 99%

Polyploidy Is Genetic Hence May Cause Non‐Adaptive Radiations, Whereas Pseudopolyploidy Is Genomic Hence May Cause Adaptive Non‐Radiations

Gorelick

Olson

2013

J Exp Zool Pt B

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“…17,22 G. biloba is one of the most notable zoidogamous gymnosperms. 23,24 Studies on the sexual reproductive process in G. biloba confirmed that when the spermatozoid is released from the pollen tube, the archegonial chamber is full of liquid, through which the spermatozoids swim. 7,17 It was thought that the liquid originated from the pollen tube, or from the degenerated nucellar tissues.…”

Section: Disclosure Of Potential Conflicts Of Interestmentioning

confidence: 99%

Structure and function of the tentpole in the reproductive process of Ginkgo biloba L.

Jin

Wang

et al. 2012

Plant Signaling & Behavior

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“…emersus to behave similarly. Hitherto polyploidy has not been reported in cycads (Gorelick & Olson 2011), making an allopolyploid origin for subsp. emersus unlikely.…”

Section: Iucn Red List Status:-inmentioning

confidence: 99%

Taxonomic notes on Encephalartos ferox (Cycadales: Zamiaceae), with the description of a new subspecies from Mozambique

et al. 2015

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Continued work on the systematics of the genus Encephalartos has been conducted over a large area along the Mozambican coast to determine the infraspecific variation and taxonomic status of Encephalartos ferox populations. The northern extent of the species was also investigated based on anecdotal information that it might represent a new taxon. Several (45) vegetative and reproductive (ca. 40) characters were analysed and used to re-circumscribe E. ferox. Literature and iconographic citations are included, as is information on ecology, cytology and conservation as available. No specimens of E. ferox were located north of the Save River in the Sofala Province, Mozambique, and the northernmost population of the species was found to be anomalous. Accordingly a new subspecies, E. ferox subsp. emersus, is recognised based on its invariably emergent stems, shorter unarmed petiole length, shorter leaves, greater number and narrower leaflets (in seedlings as well) which are more closely spaced. Strobili and peduncles in subsp. emersus are shorter and narrower with strobili having a propensity towards yellow, while internally the megasporophylls are green, grading to white away from the outer surface. The IUCN Red List status is suggested as Critically Endangered A4d + B1a,b(v) + B2a,b(v), with the threat of illegal over-collection highlighted. AbstractoEstudos contínuos sobre a sistemática do gênero Encephalartos já foram realizados sobre uma grande área ao longo da costa de Moçambique para determinar variações infra-específicas e estado taxonômico das populações de Encephalartos ferox. A extensão da espécie no norte também foi investigada, baseado em evidência anedótica que a espécie pode representar um novo grupo taxonômico. Vários (45) caracteres vegetativos e reprodutivos (ca. 40) foram analisados e usados para circunscrever Encephalartos ferox. Literatura e citações iconográficas estão incluídas, também informações sobre a ecologia, citologia e conservação como disponível. Espécimenes de Encephalartos ferox não foram encontrados norte do rio Save, na província da Sofala e as populações mais setentrionais foram consideradas anômalas. Consequentemente, uma nova subespécie, Encephalartos ferox subsp. emersus é reconhecida. Com caules invariavelmente emergentes; pecíolos mais curtos e desarmados; folhas mais curtas e quantidade maior de folíolos mais estreitos (em mudas também) e estreitamente espaçados. Estróbilos e pedúnculos de Encephalartos ferox subsp. emersus são mais curtos e estreitos, com estróbilos mais propensos para o amarelo, enquanto megasporophylls são verdes internamente, tornando brancos distante da superfície externa. O estado da espécie sobre a Lista Vermelha da IUCN é Perigo Crítico A4D + B1a,b(v) + B2a,b(v), onde a ameaça de coleção ilegal é destacada.

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Is lack of cycad (Cycadales) diversity a result of a lack of polyploidy?

Cited by 27 publications

References 127 publications

Polyploidy Is Genetic Hence May Cause Non‐Adaptive Radiations, Whereas Pseudopolyploidy Is Genomic Hence May Cause Adaptive Non‐Radiations

Polyploidy Is Genetic Hence May Cause Non‐Adaptive Radiations, Whereas Pseudopolyploidy Is Genomic Hence May Cause Adaptive Non‐Radiations

Structure and function of the tentpole in the reproductive process of Ginkgo biloba L.

Taxonomic notes on Encephalartos ferox (Cycadales: Zamiaceae), with the description of a new subspecies from Mozambique

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