Distribution of North American Earthworms Project
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... • • • • • • • • • 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
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