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Author Topic:   Imported weed diversification supports macro-evolution
Wounded King
Member (Idle past 146 days)
Posts: 4149
From: Cincinnati, Ohio, USA
Joined: 04-09-2003


Message 56 of 59 (299859)
03-31-2006 4:18 PM
Reply to: Message 53 by Speel-yi
03-31-2006 12:54 PM


Poloyploidy is one way that plants can produce new species while animals seem unable to produce fertile offspring in this manner. Another commonly seen plant that has appeared recently is the Triticum aestivum which is also a polyploid species.
They may not do so as frequently but the evidence would suggest that they can do so, for example many species of Xenopus are characterised by tetra-, octo- or even do-deca- ploidy (Evans, et al., 2004).
There is also considerable evidence for whole genome duplication events during the origin of the vertebrate and teleost lineages, such as the duplications of the Hox clusters.
TTFN,
WK

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 Message 53 by Speel-yi, posted 03-31-2006 12:54 PM Speel-yi has not replied

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Wounded King
Member (Idle past 146 days)
Posts: 4149
From: Cincinnati, Ohio, USA
Joined: 04-09-2003


Message 58 of 59 (299913)
03-31-2006 6:26 PM
Reply to: Message 57 by Minnemooseus
03-31-2006 4:36 PM


Some explanation
The various levels of ploidy relate to the number of chromosome to a basal chromosome complement (n). A mammalian gamete is usually considered haploid (n), most mammalian cells are diploid (2n) with one copy of each chromosome from each parent.
In the Xenopus family of frogs there are a number of instances of species with 4,8 and 12 times the basal complement of chromosomes:- Tetraploid (4n),Octoploid (8n) and dodecaploid (12n).
Xenopus tropicalis for example is diploid while Xenopus laevis is tetraploid, both are common laboratory animal especially in developmental biology. Tropicalis was previously named Silurana tropicalis.
The referenced paper used mitochondrial DNA to construct a phylogeny of the various species of Xenopus and tried to determine the number and extent of polyploidy events amongst the species. They estimate that polyplodisation has occurred at least 6 times amongst the species of Xenopus, since the lineages began to diverge.
TTFN,
WK

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