The study of evolutionary history and how species have developed into the modern forms we know them for today has always been a continuing and ongoing process. As new knowledge on ancient and extinct species is unearthed and matched to their evolved living descendants, we are then able to further fill out the complicated pattern in the tree of life.
But, even when comparing current organisms to those in the past, evolution is usually seen as something that occurs over far too long of a period to actively be seen in our lifespans outside of phenotypic traits from gene changes. But actual speciation is often determined after the fact. Only bacteria really reproduce swiftly enough to be evolutionarily measured directly and, even then, actual new bacterial species emerging from such study is difficult to identify.
The handful of exceptions include human activity when it comes to plants and agriculture. Active hybridization and forced polyploidy could arguably be termed to have created new species, such as triticale, a hybrid of wheat and rye. But scientists are wary of naming new species that were created by the purposeful intervention of humans. Since evolution is meant to be a random, non-controlled process, it can be said that humans making a new plant would not truly count as a new species having evolved.
A New Evolution
Today’s topic is on a plant that doesn’t fall under this definition of human intervention, but that evolved by itself just within the last 200 years. Whether it counts as an emerging species at this juncture is uncertain, but its experience of an autopolyploidy event has significantly altered its genetic structure and expression.
Researchers at the University of Stirling in Scotland have been investigating the local population of flowers belonging to the species Mimulus guttatus, otherwise known as the yellow monkeyflower.
The Mimulus genus is an interesting one. It has served as a focus of evolutionary genomics for quite some time and is considered an upcoming model organism thanks to its trait variability across populations that make it an excellent model to study phenotypic changes over time.
Being a non-native and introduced species in the UK, M. guttatus is commonly found in a form that has a diploid genome. This means that it has two sets of its genome, similar to how human chromosomes are found in a diploid state. However, when looking into the local population, the scientists found that a subset of the group instead had formed a tetraploid genome, meaning four copies.
The Effects of Autopolyploidy
This was not an unknown feat. Other ranges of M. guttatus had been found to hybridize with closely related species in the area, such as M. nasutus, thus forming this quadruple genome. But it had been hypothesized that the particular strain found in the Shetland region, which is why they were ultimately referred to as the Shetland’s monkeyflower, was not a result of hybridizing with another species, but of auto-duplication or autopolyploidy of their own genome.
Such an increase in genetic composition had direct effects on the expressed morphology and phenotype of the population, making a plant that grows larger flowers, leaves, and other parts. Though it was noted that their growth time is lengthened, taking them longer to reach their flowering period.
The researchers suggested that the one human intervention that is actually related to this, the moving of non-native plants to other ecosystems, is likely to induce evolutionary change and other incidents of not just hybridization, but also autopolyploidy. New species and subspecies are likely to be identified as indirect results of human movement and interaction.
Autopolyploidy and Future Variation
The study determined that investigating such plants will give more insights into how polyploidy affects phenotypes and range expansion for species populations. Also whether tetraploid individuals are likely to outcompete and otherwise interact with diploid members of their species.
As a method to combat environmental variability and change, polyploidy may be a valuable tool in evolution’s arsenal. It may even play a role in plant responses to climate change, allowing for better resistance to higher temperatures and droughts, among other stresses.
Photo CCs: Mimulus guttatus.Phrymaceae from Wikimedia Commons