Impact of invasive earthworms in North America
Most scientist say that in North- America, more specifically in Canada, the number of invasive earthworms has drastically surpassed the number of native earthworms. This can be seen in these next two tables.
In this table, we can see that native earthworms are pretty rare in Canada, there are even some provinces and territories that do not have any native ones. As it is possible to see in the table, the provinces and territories that have no native earthworm species would be: Saskatchewan, Manitoba, Nova-Scotia, New-Brunswick, Prince-Edward Island, Newfoundland & Labrador, Nunavut and the Northwest Territories.
Because native earthworm species are almost not present in Canada, this would mean that invasive earthworm species are necessarily present in bigger numbers across the country.
The main reason why native earthworms are almost none-existent in Canada as well as in North-America in general would because of the last Wisconsonian glaciation (also known as the Wisconsin glacial stage). This glaciation happened approximately 2.6 million years to about 11,700 years ago. The native North-American earthworms were among a long list of animal species that disappeared during the glaciation event.
Most of the invasive earthworm species that be found in north-America often originate from Europe or from Asia. These earthworms did not get to North-America on their own. Most of the time, they got here, with the help of settlers or immigrants. In some cases, the earthworms would be brought here on purpose because they were of use to the people bringing them. But it did happen that earthworms would be brought here by mistake and that they then found their way into the environment.
Once the earthworms found their way into the environment, they would end up in many different parts of North-America (especially they European earthworms). The areas where these earthworms did not all have exactly the same climate and weather patterns. This would mean that some areas had a warmer temperature while some others were colder. In terms of precipitations, some areas had more than others.
Because the European earthworms ended up in different climates in North-America, it meant that their genetic codes would be different from one area to another.
This table explains the different genetic clades that differ from earthworms from one area to earthworms from a different area. The colors represent the different genetic chrematistics that earthworms have in several areas such British Colombia, Alberta, Minnesota, Michigan as well as New-York state.
The areas where the earthworms are found do not only have an impact on the genetic codes of the earthworms, the climate and the types of precipitations also have a role to play.
What this table presents is that bioclimatic factors play a major role as well in the genetic codes that can be found in earthworms. According to the table, the temperatures and amounts of precipitation during any given amount of time will have an impact on the genetic codes of the earthworms and where they can be found.
One final aspect of the earthworms that would have an impact on were they can be found would be their molecular variance. In the next table, it is possible to see that it changes from one area to another.
In this table, it is possible to see that earthworms (for example: the L. rubellus and the L. terrestris) have a different molecular variance depending on where they are found.
Knowing that earthworms can adapt to the different environments in which it is possible to find them, it is possible to see that invasive earthworms would have negative consequences and impacts on the environment just as any other invasive species.
A good example of the consequences of the invasion of exotic earthworms would be North America (because as it was said earlier in this text, the native earthworms have disappeared due to the last Wisconsonian glaciation).
One of the impacts of invasive species of earthworms in North America would be that, according to some scientists a really negative impact on the fauna of where they are situated. The explication for scientists according to scientists would be that “[e]vidence from field and laboratory studies indicates that the restructuring of soil layers, particularly the loss of organic horizons, physical disturbance to the soil, alteration of understory vegetation, and direct competition for food resources, lead directly and indirectly to significant declines in the abundance of soil micro- and mesofauna (Migge-Kleian et all, 2006).” This would mean that the invasive species of earthworms would eat most of the food sources of the native species because they do not have any predator in North America.
Invasive earthworms in North America do not have a negative impact only on one aspect of the wildlife. They would have a negative impact on several levels of wildlife. These levels would include the microarthropods, the enchytraeidae (as well as the microfauna) and the macro- (as well as the megafauna).
The main reasons invasive earthworms would have a negative impact on the microarthropods would be according to scientists, they “[reduce] habitat complexity due to litter consumption, [compete] for organic resources, and mechanical disturbance due to earthworms processing and burrowing through the mineral soil and organic horizons (Migge-Kleian et all, 2006) ".
In the case of the enchytraeidae (as well as the microfauna), it is hard for scientists to understand how invasive earthworms negatively impact them in North America because there is not enough data available on that yet. But if we look at what is being said in Europe on this topic, we can see that “negative effects of earthworms on enchytraeid abundance appear comparable to the effects of invasive earthworms on microarthropods in other systems (Migge-Kleian et all, 2006). " This means that the enchytraeidae as well as the microfauna compete with the earthworms for resources and they suffer from physical disturbances to organic horizons.
In the case of the macro- as well as the megafauna, the invasion of earthworms has a negative impact on them because they diminish the organic horizons in the forests. Another negative impact would be that because arthropods are being impacted by invasive earthworms (and disappearing), predators who only eat them but not the earthworms, suffer as well because they have less food.
Until now, this text has covered why invasive species of earthworms are more present in North-America and why there are less native earthworm species here. This part of the text also covered how the invasive earthworm species adapted to different North-American regions (such as the Canadian provinces). To finish, this section explained how the invasive earthworm species negatively impact the wild life that was already present in the soils in those areas.
One of the most dangerous types of invasive earthworms’ species would be the earthworms who are part of the Amynthas family.
The main reason why the amynthas earthworms have a negative impact on the environment in North-America would because of their impacts on the native North-American species that can be found in our soils.
One organism that is in a constant fight of survival with amythas earthworms would be the millipedes. The main reason for that is that they compete directly with one another for the same food sources. Scientists have observed this mainly in the southern Appalachian Mountains in North-America.
During some research on how these two species live together in the wild, scientists have found that millipedes have more chances of dying prematurely because of the earthworms than of dying if they if they were not in direct competition with this invasive earthworm specie.
One of the main ways it is possible to see how the amynthas earthworms are negatively impacting the feeding cycle of the millipedes would be by studying how it changes in presence of these earthworms. To observe the changes, it is important to look at the quantity of litter produced by the millipedes alone and the quantity they produce when they are in the presence of amynthas earthworms.
In this graph, it is possible to see that millipedes produce more litter-derived C alone than in presence of the earthworms. So, it is possible to assume that they would be able to feed more alone. According to scientist even though the amynthas earthworms have an impact on the feeding process of the millipedes, the millipedes do not have a major impact on the earthworms.
At the ecosystem level, the main impacts of the amynthas earthworms would be on the carbon dynamics. This means that if there is less millipedes in the soil but more earthworms the soil would more than if there would be more millepedes than earthworms.
In this graph, it is possible the changes in the respiration rate of the soil depending on the number of millepedes and earthworms.
Another specie that would be negatively impacted by the earthworms of the amynthas type would be the terrestrial salamanders.
According to scientists, the main negative impact that the invasive amynthas earthworms have on the salamanders is that they keep the salamanders from feeding themselves. They do not keep the salamanders from feeding themselves by eating all of their food but surprisingly by making them aggressive when they are in their presence.
By looking at this graph it is possible to understand why an angry salamander would eat less when amythas earthworms are around. The main reason the salamanders eat less when amythas earthworms are around is that they use all of their energy fighting them off which leaves them almost no energy to look for food.
Invasive earthworms of the amynthas family also have a negative impact on the plants that grow on top of their soils. What they do to these plants is that they change the composition of the soil. By changing the composition of the soil, the amynthas earthworms would transform its biological, chemical and physical properties. Such changes in the soil would mean that there would be: “[a reduce] in plant species richness, a decrease in the abundance of disturbance‐sensitive plant species and an alteration of the plant community structure (Longcore et all, 2016)”.
A good way to visualise the changes caused by invasive earth worms on the soils in the forests would be by looking at the next graph.
In this graph it is possible to see how the interactions of the invasive earthworms (such as the amynthas) with the different aspects of the soils in the forests impact the different species of plants. In this graph, the doted lines mean that the interactions between the invasive earthworms and their surroundings are positive while the full black lines mean that the interactions are negative.
On a large scale, one of the best ways to control the population of invasive amythas earthworms would by with controlled fires. According to scientists, controlled fires would remove the food that the amythas earthworms would usually consume making it harder for them to feed themselves and survive.
The main food that the amythas earthworms need and that disappears because of the fire are litter and fragment litter. The burning of the soil would also cause the cocoons of the earthworms to not be viable which would cause the juvenile amythas earthworms to have a low survival rate. Scientist have also found that amynthas earthworms will not be completely wiped out by fires but it will be more difficult for their youth to survive before they hatch.
Amynthas earthworm populations are not only controlled by human induced events. They can also be controlled by natural changes in the temperature.
In this table, it is possible to see that the more we get into the less there will be amynthas earthworms in the soils. According to some scientists who studied amynthas earthworm populations over several months, most earthworms who survived later into the colder month were the longer ones who were of approximately 8.4 centimetres while the shortest earthworms who had less chances of survival had a length of approximately 5.5 centimetres.
It’s not just on the life and death of the amynthas earthworms that the different seasons and temperatures had an impact but also on their lengths.
In this table, it is possible to see how the size of earthworms of the amynthas family vary over time. The main reason why there are two colors of bars in these charts is because the black bars represent “clitellate” earthworms and the red bars represent “aclitellate” earthworms. The terms “clitellate” and “aclitellate” do not represent types of earthworms but the sexual stage they are in. The scientific definition for a clitellate earthworm would be: “Clitellates are hermaphrodites (i.e., individuals containing both male and female reproductive structures) and both male and female gonopores exit from the clitellum (Escoriza et all, 2019).”
The scientific definition for an aclitellate earthworm would be: “[…] [P]roductive individuals without a clitellum but in which genital markings are obvious (The University of British Columbia, earthworm glossary pdf).” By looking at the previous size variation table it is possible to see that clitellate earthworms varied more in sizes than the aclitellate ones.
In your communities, it might happen that you find amynthas earthworms in our gardens. If you do find some, here are some simple steps to follow according to the University of Minnesota: “Don’t move any material that might be harboring jumping worms; [r]eport any suspected jumping worms; [d]ispose of the worms in the trash, not back into the environment;[d]on’t send this to your local yard waste site, unless they follow the process for further reducing pathogens in their composting method (University of Minnesota Extension. Ask Extension, 2020).”
In conclusion, in this paper, it was possible to see that most earthworms in North-America are invasive species and they are not necessarily good for the soils and they environment. This paper has covered how most invasive species appeared in North-America and how the native species of earthworms disappeared. The most dangerous specie of earthworm that this paper covered was the amynthas earthworms. This specie of earthworms has direct impact on the environment and on species such as salamanders and millipedes. Because the amynthas earthworms have such a negative impact on the environment, scientist have started to study the best ways to keep control on these earthworms. These scientists have found that fire and cold weather have an impact on the number of amynthas earthworms. There are also guidelines that have been put in place in case civilians find these earthworms in their backyards.
Bibliography
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Migge-Kleian, S., McLean, M.A., Maerz, J.C. et al. The influence of invasive earthworms on indigenous fauna in ecosystems previously uninhabited by earthworms. Biol Invasions 8, 1275–1285 (2006). https://doi.org/10.1007/s10530-006-9021-9
Eisenhauer, N; Klein, A; Schaefer, I. Invasive lumbricid earthworms in North America—Different life histories but common dispersal? (2019). https://doi.org/10.1111/jbi.13744
Cornell Cooperative Extension / Wyoming County. Jumping Worm (Amynthas spp.). (2018, April 17). Retrieved from http://wyoming.cce.cornell.edu/agriculture/jumping-worm-amynthas-spp-1
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Bruce A. Snyder, Bas Boots, Paul F. Hendrix. Competition between invasive earthworms (Amynthas corticis, Megascolecidae) and native North American millipedes (Pseudopolydesmus erasus, Polydesmidae): Effects on carbon cycling and soil structure, Soil Biology and Biochemistry, Volume 41, Issue 7,2009, Pages 1442-1449, ISSN 0038-0717. http://www.sciencedirect.com/science/article/pii/S0038071709001321
“Salamanders: Unseen, Unheard, but NOT Unimportant” presented by Fred Schueler/Mike Oldham, Bishops Mills Natural History Centre. (2012). Retrieved from https://mvfn.ca/tag/salamanders/
Ziemba JL, Hickerson C-AM, Anthony CD (2016) Invasive Asian Earthworms Negatively Impact Keystone Terrestrial Salamanders. PLoS ONE 11(5): e0151591. https://doi.org/10.1371/journal.pone.0151591
Audel, S., Longcore, T., MacDonald, B., McCormick, M.K., Szlavecz, K., Wilson, G.W.T. and Loss, S.R. (2016), Belowground interactions with aboveground consequences: Invasive earthworms and arbuscular mycorrhizal fungi. Ecology, 97: 605-614. https://doi.org/10.1890/15-1085
Hiroshi Ikeda, Mac A. Callaham, Joseph J. O'Brien, Benjamin S. Hornsby, Evelyn S. Wenk, Can the invasive earthworm, Amynthas agrestis, be controlled with prescribed fire? Soil Biology and Biochemistry, Volume 82, 2015, Pages 21-27, ISSN 0038-0717. http://www.sciencedirect.com/science/article/pii/S0038071714004258
Gorres, Josef & Melnichuk, Ryan & Bellitürk, Korkmaz. (2014). Mortality pattern relative to size variation within Amynthas agrestis (Goto & Hatai 1899) (Oligochaeta: Megascolecidae) population in the Champlain Valley of Vermont, USA. Megadrilogica. 16. 9-14. https://www.researchgate.net/publication/285225853_Mortality_pattern_relative_to_size_variation_within_Amynthas_agrestis_Goto_Hatai_1899_Oligochaeta_Megascolecidae_population_in_the_Champlain_Valley_of_Vermont_USA
Daniel Escoriza, Jihène Ben Hassine, in Amphibians of North Africa, 2019. https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/clitellata
The University of British Columbia. Earthworm Glossary. (n.d.). Retrieved from https://ibis.geog.ubc.ca/biodiversity/efauna/documents/earthworm_glossary.pdf
University of Minnesota Extension. Ask Extension: How to get rid of Asian Jumping Worms? (2020, February 3). Retrieved from https://blog-yard-garden-news.extension.umn.edu/2020/02/ask-extension-how-to-get-rid-of-asian.html
Images
Addison, J.A. Distribution and impacts of invasive earthworms in Canadian forest ecosystems. Biol Invasions 11, 59–79 (2009). https://doi.org/10.1007/s10530-008-9320-4
Addison, J.A. Distribution and impacts of invasive earthworms in Canadian forest ecosystems. Biol Invasions 11, 59–79 (2009). https://doi.org/10.1007/s10530-008-9320-4
Eisenhauer, N; Klein, A; Schaefer, I. Invasive lumbricid earthworms in North America—Different life histories but common dispersal? (2019). https://doi.org/10.1111/jbi.13744
Eisenhauer, N; Klein, A; Schaefer, I. Invasive lumbricid earthworms in North America—Different life histories but common dispersal? (2019). https://doi.org/10.1111/jbi.13744
Eisenhauer, N; Klein, A; Schaefer, I. Invasive lumbricid earthworms in North America—Different life histories but common dispersal? (2019). https://doi.org/10.1111/jbi.13744
Cornell Cooperative Extension / Wyoming County. Jumping Worm (Amynthas spp.). (2018, April 17). Retrieved from http://wyoming.cce.cornell.edu/agriculture/jumping-worm-amynthas-spp-1
Millipede. (2019). Retrieved from https://www.britannica.com/animal/millipede
Bruce A. Snyder, Bas Boots, Paul F. Hendrix. Competition between invasive earthworms (Amynthas corticis, Megascolecidae) and native North American millipedes (Pseudopolydesmus erasus, Polydesmidae): Effects on carbon cycling and soil structure, Soil Biology and Biochemistry, Volume 41, Issue 7,2009, Pages 1442-1449, ISSN 0038-0717. http://www.sciencedirect.com/science/article/pii/S0038071709001321
Bruce A. Snyder, Bas Boots, Paul F. Hendrix. Competition between invasive earthworms (Amynthas corticis, Megascolecidae) and native North American millipedes (Pseudopolydesmus erasus, Polydesmidae): Effects on carbon cycling and soil structure, Soil Biology and Biochemistry, Volume 41, Issue 7,2009, Pages 1442-1449, ISSN 0038-0717. http://www.sciencedirect.com/science/article/pii/S0038071709001321
“Salamanders: Unseen, Unheard, but NOT Unimportant” presented by Fred Schueler/Mike Oldham, Bishops Mills Natural History Centre. (2012). Retrieved from https://mvfn.ca/tag/salamanders/
Ziemba JL, Hickerson C-AM, Anthony CD (2016) Invasive Asian Earthworms Negatively Impact Keystone Terrestrial Salamanders. PLoS ONE 11(5): e0151591. https://doi.org/10.1371/journal.pone.0151591
Audel, S., Longcore, T., MacDonald, B., McCormick, M.K., Szlavecz, K., Wilson, G.W.T. and Loss, S.R. (2016), Belowground interactions with aboveground consequences: Invasive earthworms and arbuscular mycorrhizal fungi. Ecology, 97: 605-614. https://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/15-1085
Hiroshi Ikeda, Mac A. Callaham, Joseph J. O'Brien, Benjamin S. Hornsby, Evelyn S. Wenk, Can the invasive earthworm, Amynthas agrestis, be controlled with prescribed fire? Soil Biology and Biochemistry, Volume 82, 2015, Pages 21-27, ISSN 0038-0717. http://www.sciencedirect.com/science/article/pii/S0038071714004258
Gorres, Josef & Melnichuk, Ryan & Bellitürk, Korkmaz. (2014). Mortality pattern relative to size variation within Amynthas agrestis (Goto & Hatai 1899) (Oligochaeta: Megascolecidae) population in the Champlain Valley of Vermont, USA. Megadrilogica. 16. 9-14. https://www.researchgate.net/figure/Size-variation-of-Amynthas-agrestis-on-the-sampling-dates-A-September-16-B-September_fig2_285225853
Gorres, Josef & Melnichuk, Ryan & Bellitürk, Korkmaz. (2014). Mortality pattern relative to size variation within Amynthas agrestis (Goto & Hatai 1899) (Oligochaeta: Megascolecidae) population in the Champlain Valley of Vermont, USA. Megadrilogica. 16. 9-14. https://www.researchgate.net/figure/Size-variation-of-Amynthas-agrestis-on-the-sampling-dates-A-September-16-B-September_fig2_285225853
Daniel Escoriza, Jihène Ben Hassine, in Amphibians of North Africa, 2019. https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/clitellata
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