Evolution Genomics News

New species originated via polyploidy?

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New species Mimulus peregrinus/University of Stirling

Basically, a new polyploid plant species has had more than one separate origin in Scotland. And we still don’t know how that works.*

Polyploidy—the heritable condition of possessing more than two complete sets of chromosomes—has always been something of a mystery, and this new find both illuminate it and suggests we should pay more attention to it:

Polyploidy is the heritable condition of possessing more than two complete sets of chromosomes. Polyploids are common among plants, as well as among certain groups of fish and amphibians. For instance, some salamanders, frogs, and leeches are polyploids. Many of these polyploid organisms are fit and well-adapted to their environments. …

Well, from ScienceDaily:

Dr Vallejo-Marin added: “It is impossible to say whether Mimulus peregrinus evolved first in the south or in the north of Scotland, but our discovery of a very young species of this kind has allowed us to study evolution as it happens. We only know of a handful of other plant species as young as Mimulus peregrinus and so in this respect it is like looking at the big bang in the first milliseconds of its occurrence.

“The process of evolution it has followed is particularly interesting and adds complexity to our conception of the tree of life. Instead of branching out as it grows, Mimulus peregrinus is an example of how some branches can come back together again and spawn new species that are in part the combination of their ancestors.”

Which makes it kind of difficult to track evolution. Yes it happens, but not like the Darwin lobby rams into textbooks.

Here’s the abstract:

Whole genome duplication (polyploidisation) is a mechanism of “instantaneous” species formation that has played a major role in the evolutionary history of plants. Much of what we know about the early evolution of polyploids is based upon studies of a handful of recently formed species. A new polyploid hybrid (allopolyploid) species Mimulus peregrinus, formed within the last 140 years, was recently discovered on the Scottish mainland and corroborated by chromosome counts. Here, using targeted, high-depth sequencing of 1200 genic regions, we confirm the parental origins of this new species from M. x robertsii, a sterile triploid hybrid between the two introduced species M. guttatus and M. luteus that are naturalised and widespread in the United Kingdom. We also report a new population of M. peregrinus on the Orkney Islands and demonstrate that populations on the Scottish mainland and Orkney Islands arose independently via genome duplication from local populations of M. x robertsii. Our data raise the possibility that some alleles are already being lost in the evolving M. peregrinus genomes. The recent origins of a new species of the ecological model genus Mimulus via allopolyploidisation provide a powerful opportunity to explore the early stages of hybridisation and genome duplication in naturally evolved lineages. (paywall) – Mario Vallejo-Marín, Richard J. A. Buggs, Arielle M. Cooley, Joshua R. Puzey. Speciation by genome duplication: Repeated origins and genomic composition of the recently formed allopolyploid speciesMimulus peregrinus. Evolution, 2015; DOI: 10.1111/evo.12678

* See Douglas E. Soltis, Richard J. A. Buggs, Jeff J. Doyle and Pamela S. Soltis (2010) What we still don’t know about polyploidy Taxon 59: 1387-1403:

ABSTRACT During the past decade there has been a tremendous resurgence of interest in polyploidy that has in large part been stimulated by the development of increasingly powerful genetic and genomic tools. The result has been numerous new insights into the genomic and genetic consequences of polyploidy. The plethora of new discoveries has dramatically reshaped traditional views and concomitantly revealed that polyploidy is a highly dynamic and ubiquitous process. These recent advances in our understanding of polyploidy have stimulated numerous reviews, most focused on the various genetic, epigenetic, and genomic consequences of polyploid evolution. Whereas genetic and genomic attributes of polyploidization have received considerable attention, other crucial areas of polyploid evolution have received much less (e.g., ecology, pollination biology, physiology). The focus of this paper is not to review again recent discoveries, but to emphasize what we do not yet know about polyploidy, which despite all that has been learned about genome doubling is still an enormous amount. Our list is not meant to be comprehensive, but includes a range of topics that we have placed in several general categories, including mode of formation, ecological and physiological consequences, and genomic rules. Questions include: What is (are) the most frequent mechanism(s) of polyploidization? What factors promote/facilitate polyploidization? What factors favor autopolyploid vs. allopolyploid formation? Do multiple origins result in lineages with differing evolutionary trajectories and/or cryptic species? Our major goals are to stimulate discussion and promote further research. Download.

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2 Replies to “New species originated via polyploidy?

  1. 1
    Dionisio says:

    a new polyploid plant species has had more that one separate origin in Scotland

    than?

    Please, you may remove this post as soon as you read it. Thanks.

  2. 2
    bornagain77 says:

    Of related interest:

    Double Your Pleasure: What Exactly Can You Get from Polyploidy? – October 10, 2014
    Excerpt: “Stebbins viewed polyploid species as genetically depauperate with limited evolutionary potential. A new polyploidy species was envisioned as forming via a single polyploidization event and would therefore exhibit a high degree of genetic uniformity across individuals. Following this model of formation, an allopolyploid would exhibit no homologous, or segregating, variation, only homeologous (nonsegregating) variation. Furthermore, if a mutation were to arise in the polyploid, its effect would be masked by either the presence of a homeologous locus (in an allotetraploid) or multiple alleles (in an autopolyploid). Although not impossible, the fixation of a new mutation is much slower in a polyploid than in its diploid parents. Stebbins (1971 , p. 127) correctly noted that “…the large amount of gene duplication dilutes the effects of new mutations… polyploids have great difficulty evolving truly new adaptive gene complexes” and that “…chromosome doubling will most often have a retarding effect on evolutionary change via mutation, genetic recombination, and selection.” Furthermore, this buffering effect of multiple genomes may extend to the origins of morphological variation in a polyploid (Stebbins, 1950 , 1971 [pp. 147-148]): “Very often, even in complexes on which the basis of phytogeographical evidence must be regarded as hundreds of thousands or even millions of years old, the range of morphological variability encompassed by all of the tetraploids is less than the total range of that found among the diploids…”,,,
    http://www.evolutionnews.org/2.....90311.html

    John Sanford, a leading expert in plant genetics, examines the Polyploidy (Gene/Chromosome Duplication) claims of Darwinists in Appendix 4 of his book “Genetic Entropy and the mystery of the Genome”.

    “What about polyploidy plants? It has been claimed that since some plants are polyploidy (having double the normal chromosome numbers), this proves that duplication must be beneficial and must increase information. Polyploidy was my special area of study during my Ph.D. thesis. Interestingly, it makes a great deal of difference how a polyploid arises. If somatic (body) cells are treated with the chemical called colchicine, cell division is disrupted , resulting in chromosome doubling – but no new information arises. The plants that result are almost always very stunted, morphologically distorted, and generally sterile. The reason for this should be obvious – the plants must waste twice as much energy to make twice as much DNA, but with no new genetic information! The nucleus is also roughly twice as large, disrupting proper cell shape and cell size. In fact, the plants actually have less information than before, because a great deal of the information which controls gene regulation depends on gene dosage (copy number). Loss of regulatory control is loss of information. This is really the same reason why an extra chromosome causes Down’s Syndrome. Thousands of genes become improperly improperly regulated, because of extra genic copies.
    If somatic polyploidization is consistently deleterious, why are there any polyploidy plants at all – such as potatoes? The reason is that polyploidy can arise by a different process – which is called sexual polyploidization.This happens when a unreduced sperm unites with a unreduced egg. In this special case, all of the information within the two parents is combined into the offspring, and there can be a net gain of information within that single individual. But there is no more total information within the population. the information within the two parents was simply pooled. In such a case we are seeing pooling of information, but not any new information.”,,, “in some special cases, the extra level of gene backup within a polyploidy can outweigh the problems of disrupted gene regulation and reduced fertility – and so can result in a type of “net gain”. But such a “net gain” is more accurately described as a net reduction in the rate of degeneration.”
    John Sanford – Genetic Entropy & The Mystery of the Genome – pages 191-192 –

    Of note: Dr. John Sanford has been a Cornell University Professor for more that 25 years (being semi-retired since 1998). He received his PhD. from the University of Wisconsin in the area of plant breeding and plant genetics.,,, His most significant scientific contributions involved three inventions – the biolistic (“gene gun”) process, pathogen-derived resistance, and genetic immunization. Most of the transgenic crops grown in the world today were genetically engineered using the gene gun technology developed by John and his collaborators.

    Dr. Wolf-Ekkehard Lönnig, (retired) Senior Scientist (Biology) at the Max Planck Institute for Plant Breeding Research in Cologne, Germany, has also done extensive research on plant breeding and is also, to put it mildly, unimpressed with Darwinian claims of speciation:

    Peer-Reviewed Research Paper on Plant Biology Favorably Cites Intelligent Design and Challenges Darwinian Evolution – Casey Luskin December 29, 2010
    Excerpt: Many of these researchers also raise the question (among others), why — even after inducing literally billions of induced mutations and (further) chromosome rearrangements — all the important mutation breeding programs have come to an end in the Western World instead of eliciting a revolution in plant breeding, either by successive rounds of selective “micromutations” (cumulative selection in the sense of the modern synthesis), or by “larger mutations” … and why the law of recurrent variation is endlessly corroborated by the almost infinite repetition of the spectra of mutant phenotypes in each and any new extensive mutagenesis experiment instead of regularly producing a range of new systematic species…
    (Wolf-Ekkehard Lönnig, “Mutagenesis in Physalis pubescens L. ssp. floridana: Some Further Research on Dollo’s Law and the Law of Recurrent Variation,” Floriculture and Ornamental Biotechnology Vol. 4 (Special Issue 1): 1-21 (December 2010).)
    http://www.evolutionnews.org/2.....42191.html

    Dr. Wolf-Ekkehard Lönnig, (retired) Senior Scientist (Biology), Max Planck Institute for Plant Breeding Research, Emeritus, Cologne, Germany.

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