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Besieged by destructive plants and animals? Blame epigenetics

Plants and animals that are seemingly harmless in their native habitats can become quite aggressive or even destructive in a new location. Think of the rats that have been a source of human and animal…

The Indian Myna is an invasive species – but has its behaviour changed in Australia? Wikimedia Commons.

Plants and animals that are seemingly harmless in their native habitats can become quite aggressive or even destructive in a new location.

Think of the rats that have been a source of human and animal diseases for generations and the kudzu, purple loostrife and other plants that wreak havoc in otherwise natural habitats.

These “invasive” organisms have potentially devastating biological and economical ramifications. Mosquitos introduced to Hawaii carried avian malaria, which decimated native birds, and millions of dollars goes annually to eliminating or controlling nuisance plants such as the Brazilian pepper.

Recent studies suggest epigenetics – changes to the packaging of DNA that affect how genes get expressed – may play a role in why some plants and animals cause so much trouble outside their native ranges.

Invasion alert

When a species invades a new area, only a few plants or animals establish a new population. Biological theory predicts that this limited number of organisms limits a species’ variation and therefore the potential for evolution by natural selection.

Despite these expected limitations, many invasive species appear to thrive even with low levels of genetic variation.

In a recent study of the highly invasive Japanese knotweed (Fallopia japonica) published in Ecology Letters, plants across the 160km of Long Island, New York had almost no genetic variation.

Instead their response to new habitats (such as sand dunes and marshes) was related to DNA methylation, a type of epigenetic mechanism that alters gene expression.

Japanese knotweed is here seen expanding into farmland in western Virginia. US Fish and Wildlife Service - Northeast Region

Epigenetics: the making of an invader?

Gene expression is the process whereby the DNA of an organism is translated to a particular function or behaviour of that organism.

The knotweed findings indicate that epigenetic effects such as DNA methylation alters gene expression and could influence how the plants manage to thrive in diverse habitats. Even though they have basically the same DNA, the genes expressed by each plant vary based on the environment they’re placed in.

Similarly, in house sparrows, one of the world’s most common birds, invasive populations have adjusted quickly to novel conditions in Africa.

Over the short span of 60 years, house sparrows have spread across Kenya, changing dramatically as they’ve moved into new areas.

In Kenya they fight parasites differently, respond to stress differently, and are much more exploratory in their behaviour.

House sparrows have changed their behaviour over the 60 years they’ve been in Kenya. Sergey Yeliseev

With so little genetic variation to work with, it’s very likely that epigenetics is helping this invader expand its range. Although genetic variation in these populations is low compared to most other parts of the world, epigenetic variation is so high that no two individuals are similar epigenetically.

This indicates that while the genomes may be similar at the DNA sequence level, the expression of the DNA might vary quite a lot among individuals.

Epigenetics and the future of invasions

So, even though two individuals may have the same DNA sequence, their behaviour, health, size and many other traits can differ quite a bit just because different portions of the genome are activated or deactivated.

Some of these environmentally induced changes can be inherited, thus having a more persistent effect on traits within the species. Inheritance of environmentally induced epigenetic effects essentially provides a mechanism for inheritance of acquired traits, which has long been disregarded in biological circles.

Historically, novel variation was thought to emerge only via mutations in DNA sequence, which means that changes in populations would happen relatively slowly - over thousands if not millions of years in most cases.

In light of epigenetics though, the environment has two roles: environment still “selects” the individuals that get to breed, or in other words it sorts among the mutants that arise in DNA sequences.

But epigenetic changes induced by the environment also reveal trait variation through gene expression. If such epigenetic variation is heritable, trait change can show up faster in populations than would occur by traditional sequence-based evolution.

For those reasons, it’s not surprising that invasive species have been the basis of many ecological epigenetics studies.

Because epigenetics research reveals how the genome translates into important traits in response to environmental factors, this work is having a broad impact, on our understanding of issues as diverse as obesity, cancer rates, and how species may react to global climate change.

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9 Comments sorted by

  1. Forth Sadler

    logged in via Facebook

    I fond myself wondering about the effects of this on humans. Not just with a given subset moving from one area to another in a process of colonisation but also with regards to the change in our living conditions as we become more urbanised with the changes in population density, availability of food, artificial lighting and so on that implies. Are we the same beasties that we were pre-industrialisation?

  2. Fred Pribac

    logged in via email

    Nice article ... now ... let's just hope there's a beneficial epigentic change that kicks in at say +1.5 degrees of climate warming.

    1. Emma Anderson

      Artist and Science Junkie

      In reply to Fred Pribac

      More malaria carrying mozzies to kill off people who don't have sickle cells (i.e most of us)

      End of population crisis!

  3. Greg Boyles

    Lanscaper and former medical scientist

    Could be a very useful avenue along which to investigate biological control of these invasive species.

    Does anyone know of any scientistist in Australia who are investigating this as a means of biological control?

  4. Derek Bolton

    Retired s/w engineer

    " the genes expressed by each plant vary based on the environment they’re placed in."
    It would be interesting to know how this works. I can think of two possibilities:
    1. A repertoire of epigenetic adaptations to a range of environmental variables is provided by the genes. That is, the DNA has evolved a specific set of heritable responses the organism can make to certain environmental challenges (as is the case for many other adaptations) - it's just that in this case the mechanism for adapting involves silencing of genes.
    2. Methylation, though inherited, is subject to a much higher 'mutation rate' than the DNA itself, so it can provide a faster adaptation path. In this model, the changes in methylation through generations are as undirected as DNA mutation. If so, even after adapting well, the population should show a much higher epigenetic variability than genetic one.

  5. LP Hock


    When I was a child, we find Myna bird intelligent and nice to keep as pet in bigger cage. Myna birds were few in numbers. Today, the country is full of Myna birds in the urban and in rural areas, crows. Singapore is a clean nation and stray dogs and cats and even rats are rare these days due to large plastic containers for keeping rubbish and food wastes. I can't understand the larger population of Myna birds.

    1. John Holmes

      Agronomist - semi retired consultant

      In reply to LP Hock

      Re rats - sure less food less numbers but also better at hiding?

  6. John Holmes

    Agronomist - semi retired consultant

    Not surprised at this suggestion. However, remember that the whole basis of biological control is based on the concept that the alien is here with out the normal associated organisms with which it hares it original niche. This allows more freedom to grow. We use pesticides in crops to achieve the same thing. Just look at the contrast in significance of 'weeds of South African origin' in Australia and their significance in their home range. 'Double gee" any one? Conversely we have had a number…

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    1. John Holmes

      Agronomist - semi retired consultant

      In reply to John Holmes

      Can we please have an edit function for those of us who's English mechanics is less than perfect.