Polyploidy rocks!!

Polyploidy and ecological adaptation in wild yarrow. 
Ramsey J.

Abstract

Chromosome evolution in flowering plants is often punctuated by polyploidy, genome duplication events that fundamentally alter DNA content, chromosome number, and gene dosage. Polyploidy confers postzygotic reproductive isolation and is thought to drive ecological divergence and range expansion. The adaptive value of polyploidy, however, remains uncertain; ecologists have traditionally relied on observational methods that cannot distinguish effects of polyploidy per se from genic differences that accumulate after genome duplication. Here I use an experimental approach to test how polyploidy mediates ecological divergence in Achillea borealis (Asteraceae), a widespread tetraploid plant with localized hexaploid populations. In coastal California, tetraploids and hexaploids occupy mesic grassland and xeric dune habitats, respectively. Using field transplant experiments with wild-collected plants, I show that hexaploids have a fivefold fitness advantage over tetraploids in dune habitats. Parallel experiments with neohexaploids-first-generation mutants screened from a tetraploid genetic background-reveal that a 70% fitness advantage is achieved via genome duplication per se. These results suggest that genome duplication transforms features of A. borealis in a manner that confers adaptation to a novel environment.

Proc Natl Acad Sci U S A. 2011 Mar 14. [Epub ahead of print]

Why is this cool?

  First off, what does polyploidy mean? What is a ploid? It is a suffix that means chromosome (a loose summary, but whatever). Humans are diploids meaning that we have two copies of our genome/chromosomes in each cell. Most bacteria are monoploids meaning that they got just one copy of their genome/chromosome. Plants are fantastically unique because they can have many copies of their genome/chromosomes in each cell. 

 Today's paper seeks to understand the effects of polyploidy by comparing plants that have differing numbers of genome copies. The researcher compare six copy plants (hexaploids) against four copy plants (tetraploids) in two different environments and sees differences in growth between the two types. The results of the experiments is that hexaploids are better adapted for their environment than tetraploids, but didn't the hexaploid evolve to survive in that environment? Well, the researcher was able to isolate a hexaploid plant from the tetraploid population and it had increased growth than the tetraploid!

 Some of you might be thinking that since plants have so much genetic material, shouldn't they be super intelligent or absurdly complex like humans? Good thoughts, but the answer is no. Plants have a different evolutionary history that doesn't depend on intelligence. Imagine a plant as Helm's Deep, a stationary fortress to hold off any kind of attack. Now consider humans as tanks, they move around and just blow everything up. These are two different strategies necessary to accomplish these goals. As for complexity, I think the better question is: can humans ever be as complex as plants? Plants can communicate with one another. Some can live hundreds of years. Many are entrenched in a vital process that is indispensable to life on Earth. Where do the humans stand?

 What about a human plant hybrid? Which is your favorite?

 My favorite: Man-Thing.