Polyploidy. Part 5: Patterns of Autopolyploidy

switchgrass, Panicum virgatum, famous autopolyploid

Polyploidy is whole genome duplication, uncommon in animals, but common in plant evolution, between living plant species and in individuals within plant species. (See previous blogs link). Although it is actually a continuum, botanists recognize allopolyploidy, when the genomes that duplicated come from two different species and autopolyploidy when a single genome doubles. This post is about autopolyploids.

Polyploidy 4. Distribution of Autopolyploidy

Polyploidy is whole genome duplication, a genetic phenomenon which is widespread in plants and uncommon in animals. The ancestry of most if not all plants includes a doubling of all the chromosomes. In addition, many plant species were formed by crossing between two existing species, with subsequent doubling of the genome which made the hybrid fertile. (See previous blogs Intro to Polyploidy, Crop Plant Polyploidy, Speciation via Polyploidy).

 

Long known and still poorly understood is variation in polyploidy within a species. 

fireweed (Chamerion) has within-species polyploidy
 

Plant Story -- Strawberries. Fragaria, Beloved Fruits 1. Distribution and Botany

Strawberries, genus Fragaria in the rose family, Rosaceae, are a popular fruit and have been for millennia. Twenty to 24 species are recognized, with cultivated strawberries adding many hybrids and varieties. They are native around the world, mainly in the northern part of the Northern Hemisphere, plus a few Southern Hemisphere species.

strawberries, Fragaria

Polyploidy Part 2. And Crop Plants

Polyploidy is whole genome duplication, where all the chromosomes double. Animals rarely survive major chromosome changes, but plants usually do, leading to aspects of plant genetics that are quite different from animals. 

strawberry, Fragaria ananassa

Even though you cannot easily spot a polyploid by looking at it, polyploidy is not obscure. Many common, important plants are polyploid, for example bread wheat (Triticum aestivum), white potatoes (Solanum tuberosum), coffee (Coffea arabica), sweet potatoes (Ipomoea batatas), strawberries (Fragaria x ananassa) and cotton (Gossypium tomentosum). Researchers estimate that 75% of all plants, and likewise, 75% of crops, are polyploids.  

Polyploidy, Multiple Copies of the Genome. Part 1. Basics

One peculiar characteristic of plants, not much shared by animals, is polyploidy, multiple copies of all the chromosomes. In plants and animals, DNA, the genetic material, is bound up in protein-wrapped bodies called chromosomes. Organisms have several to many chromosomes, usually as pairs. For animals, each species has a characteristic number--humans 23 pairs, dogs 39 pairs--with very little variation. One of the ways that plants are DIFFERENT is that chromosome number can vary a lot, between species but also between plants of the same species growing next to each other.  

carrots, flowering

Plant Story - Yarrow, Achillea millefolium, a plant species complex

Achillea millefolium, yarrow

Yarrow, Achillea millefolium (sunflower family, Asteraceae) is a small perennial plant found around the world. It is a medicinal herb in both modern and traditional medicines (see previous post: link) and is an attractive, easily-grown garden flower and in some places, a weed.


Very few plant species are listed as native to Europe, Asia and North America but that is the case for Achillea millefolium.  

Actually, yarrow is what botanists call a species complex. I will outline the situation as I understand it, because this sort of complexity is surprisingly common in plants, although yarrow does it particularly well.