Plant Speciation

Gene and Genome Duplications in Plants

“…Polyploidy has been studied in plants for 100 years (Lutz, 1907;Gates, 1909;Kuwada, 1911), with early investigators of the topic now comprising a "who's who" of prominent plant evolutionists and geneticists (e.g., Winge, 1917;Müntzing, 1936;Darlington, 1937;Clausen et al, 1945;Stebbins, 1947Stebbins, , 1950Löve and Löve, 1949;Lewis, 1980a;Grant, 1981).…”

“…For example, both Müntzing (1936) and Darlington (1937) suggested that about 50% of all angiosperm species were polyploid, while Stebbins (1950) later estimated the frequency of polyploidy in angiosperms at 30 to 35%. Using a cutoff point of n = 14, Grant (1963Grant ( , 1981 inferred that 47% of all flowering plants were of polyploid origin and proposed that 58% of monocots and 43% of "dicots" (his usage) were polyploid. Using additional chromosome counts and the same methods and cutoff as Grant, Goldblatt (1980) subsequently recalculated the frequency of polyploidy in the monocots to be 55%.…”

“…Evolutionary dynamics of genes duplicated via polyploidy are also likely to differ from those accompanying either tandem duplications or small-scale chromosomal duplications, most important because the stoichiometry of duplicate genes is maintained following WGD, allowing for divergence and modification not only of single genes but conceivably, of gene networks. Polyploidy has long been considered an important mechanism of speciation and of genomic change (e.g., Darlington, 1937;Clausen et al, 1945;Stebbins, 1950;Grant, 1981), but its fundamental role in genome evolution (not only in plants but also other eukaryotes, yeast (Kellis et al, 2004), and vertebrates [reviewed by Furlong and Holland (2004)] is only beginning to be appreciated.…”

Reconciling Phylogenetic Trees

“…Gene families and genomes have been shaped by ancient events of genome duplication that have taken place during the evolution of species (Stebbins, 1950;Grant, 1981). The location and timing of these genome duplications can provide invaluable information in understanding how gene families and genomes have evolved.…”

2. Genome rearrangement and speciation in freshwater algae

“…Especially, the Euglenophyceae, the Cryptophyceae, the Dinophyceae and the Zygnematophyceae contain many species with extremely high chromosome numbers of over one hundred (Sarma, 1982). According to Grant (1981), in higher plants, species with the gametic chromosome numberofn = 14 or more can be classified as polyploid. Although we know only a few examples of polyploid series of related species in algal taxa (Khan et al, 1984), species with such a high chromosome number, and perhaps also many others with chromosomes of more than some tens, which are widely scattered in almost all the cytologically studied orders (Sarma, 1982), are no doubt of polyploid origin.…”