Factors affecting the distribution of
earthworms in North America
A collaborative project involving faculty at PUIs
and their students
Timothy McCay
Biology & Environmental Studies, Colgate University, Hamilton, New York
Christine Hopfensperger
Biological Sciences, Northern Kentucky University, Highland Heights, Kentucky
“It may be doubted whether there are many other animals which have played so
important a part in the history of the world, as have these lowly organized
creatures.”
Charles Darwin 1881
The Formation of Vegetable Mould through the Action of
Worms, with Observations on their Habits
Lumbricus terrestris
Drawn by Nga Nguyen ‘15
No Earthworms
Many Earthworms
Great Lakes Worm Watch
http://www.nrri.umn.edu/WORMS
Nearctic Earthworms
Hendrix and Bohlen 2002. Exotic earthworm invasions. BioScience 52: 801-811.
Reynolds, JW. 1995. Status of exotic earthworm systematics and biogeography in North America. In
Earthworm Ecology and Biogeography (Hendrix PF, ed.) 801-811.1-27
Hungry, voracious … and an invasive species: Asian “crazy
worm” has emerged in Wisconsin
MADISON (WITI) — Wisconsin’s newest invasive species has
done its best to stay underground, but the voracious,
numerous and mysterious Asian crazy worm (Amynthas
agrestis) has emerged for the first time in the state on the
campus of the University of Wisconsin–Madison.
16 July 2014, Katie Delong, FOX6NOW.com
Modern American Earthworm Fauna
1. Native species
2. Introduced European species
3. Introduced Asian species
Lumbricus terrestris = EUROPE
Bimastos = NATIVE
Amynthas = ASIA
Factors Affecting the Colonization of central New
York State by Exotic Earthworms
1. How completely “earthworm-colonized” is the
central New York landscape?
2. What limits the distributions of earthworms?
0.6 m
5m
Matt Zimmerman ‘11
Species
75 sites
about 2,500 Worms
Allolobophora chloritica
Amynthas agrestis
Amynthas hupeiensis
Aporrectodea icterica
Aporrectodea longa
Aporrectodea rosea
Asia
Asia
Aporrectodea turgida
Bimastos parvus
native
Dendrobaena octaedra
Dendrodrillus rubidus
Eiseniella tetraedra
Eisenioides lonnbergi
Lumbricus castaneus
Lumbricus rubellus
Lumbricus terrestris
Octolasion lacteum
Octolasion tyrtaeum
native
Worms
Detected
No Worms
Detected
Forests
41
19 (32%)
Open Habitats
15
0
Why are certain areas free of earthworms?
H1: Earthworms have not yet arrived in these locations
H2: Earthworms cannot tolerate conditions in these
locations
Factors affecting site
suitability
Soil pH
Soil organic fraction
Slope*
Elevation*
Aspect*
Potential wetness*
Solar radiation*
Factors affecting dispersal
Distance to roads*
Distance to clearing*
Distance to streams*
* Calculated using location and geographic information systems tools
R2= 0.23
Distance to nearest
road
Slope = -0.01
P = 0.034
pH
Slope = 0.26
P = 0.016
H1: Earthworms have not yet arrived in
these locations
H2: Earthworms cannot tolerate
conditions in these locations
Evidence: sites far from roads have fewer
species
Evidence: sites with low pH have fewer
species
The Ecological Research as Education Network
EREN Project Questions
What are the distributional limits and habitat associations of the
various earthworm species of North America?
What factors limit the presence of different species – biogeographic
factors or habitat quality? How completely “worm-invaded” is the
landscape in different parts of North America?
Are worm communities structured predictably?
Collaborators (to date)
13 collaborators
33 sites in 9 states
1550 earthworm records (60% specimens examined)
Species
Ubiquity Index
(% sites)
Octolasion tyrtaeum
35
Lumbricus rubellus
33
L. terrestris
31
Dendrobaena octaedra
28
Apporectodea caliginosa
23
Octolasion tyrtaeum
Ap. rosea
17
(CU no. 40018, Madison
County, NY)
L. castaneus
15
Oc. cyaneum
14
Dendrodrilus rubidus
10
…
Eiseniella lonnbergi
5
Amynthas agrestis
3
Eiseniella lonnbergi
(CU no. 27655, Madison
County, NY)
Challenge
proper taxonomic determination
Challenge
fitting the exercise in the context of a class lab
Wiki page at PBworks for sharing curriculum ideas
Learning Goals
1. Students will better articulate the functional value of biodiversity and understand
that different earthworm species have different functional roles in the
environment
2. Students will be able to describe the role of earthworms in ecosystem processes
3. Students will understand that earthworms are the subject of several common
misconceptions and that evaluations of the value of earthworms in ecosystems is
complicated.
4. Students will be able to describe the long history of earthworm colonization and
movements in North America and some of the disagreements and controversies
regarding the history of earthworm colonization.
5. Students will understand how the concept of habitat changes with scale and is
taxon specific.
Learning Assessment
“What do you know about earthworms in North America?”
Things to look for in the response: evidence that students...
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know that there are multiple species of earthworm
know that the effects of earthworms can possibly be negative on other species in
the system
recognize that earthworms fall within different functional roles
know that earthworms act to decompose dead plant matter
know some of the abiotic conditions that are important in determining habitat
quality
know that some of the earthworms, including many common species, in North
America are believed to be exotic to the continent
can describe the connection between glacial history and earthworm colonization
know that earthworms play a role in nutrient cycling
know that earthworms change the quality of soils, including soil aeration
Conclusions and Insights
1. A collaborative project can reveal more about the
dynamic distributions of invasive species than projects
at a single site
2. Perhaps not surprisingly, the proper identification of
taxa has been our greatest challenge
3. Earthworms have promise as the subject of labs with
various learning objectives