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Distribution and Habitat of the Endemic Earthworm Eisenoides lonnbergi (Michaelsen) in the Northeastern United States
Timothy S. McCay, Rebecca A. Pinder, Eric Alvarado, and Watson C. Hanson

Northeastern Naturalist, Volume 24, Issue 3 (2017): 239–248

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Northeastern Naturalist Vol. 24, No. 3 T.S. McCay, R.A. Pinder, E. Alvarado, and W.C. Hanson 2017 239 2017 NORTHEASTERN NATURALIST 24(3):239–248 Distribution and Habitat of the Endemic Earthworm Eisenoides lonnbergi (Michaelsen) in the Northeastern United States Timothy S. McCay1,*, Rebecca A. Pinder2, Eric Alvarado1, and Watson C. Hanson1 Abstract - Eisenoides lonnbergi is one of just a few native earthworm species known from north of the most recent glacial maximum and has been found most commonly in saturated soils. We sampled earthworms from wetlands in Upstate New York and compiled published and unpublished records of E. lonnbergi to better describe the distribution and habitat associations of this species in the Northeast. We found E. lonnbergi at 14 of 22 sampled sites, including 8 of 14 riparian areas and 6 of 8 wetlands of other types (bogs, fens, and swamps). Soil pH at colonized sites varied from 3.4 to 8.5. At the 3 most acidic sites, E. lonnbergi was the only species detected by our sampling. Published records with habitat data also support an association between E. lonnbergi and wetland habitats of variable pH, both above and below the most recent glacial maximum. Eisenoides lonnbergi is strongly associated with wetlands, including some habitats, such as acidic bogs, in which it may be the only earthworm present. Land managers and conservation biologists should consider Eisenoides lonnbergi along with other native species sensitive to the loss of wetlands in the Northeast. Introduction Approximately one-third of earthworm species found in North America north of Mexico are believed to have been introduced from Europe and Asia (Blakemore 2008, Hendrix et al. 2008, Reynolds 1995). In particular, non-native taxa dominate the earthworm fauna of previously glaciated northeastern North America (Hendrix and Bohlen 2002, Reynolds 2010, 2016). Of those species hypothesized to be endemic to eastern North America, only 4 have been documented north of the southern limit of the most recent glacial maximum: Bimastos parvus (Eisen), B. tumidus (Eisen), Eisenoides lonnbergi (Michaelsen), and Sparganophilus eiseni Smith (Reynolds 2010). Interestingly, these species all seem to be associated with mesic habitats, at least in the Northeast (James 1995, Reynolds 2010), suggesting either that mesic habitats represent a refuge for native earthworms within an upland landscape dominated by exotics or that mesic habitats may have been more conducive to dispersal and recolonization following glacial retreat. Eisenoides lonnbergi has been called a “semi-aquatic species” (James 1995) and a “freshwater oligochaete” (Tillinghast and Huffman 1973). It is known primarily from wetlands with saturated soils and has been collected from muddy substrates beneath standing water (Gates 1955, James 1995). This species has 1Department of Biology, Colgate University, Hamilton, NY 13346. 2Division of Science, Columbia-Greene Community College, Hudson, NY 12534. *Corresponding author - tmccay@colgate.edu. Manuscript Editor: Peter K. Ducey Northeastern Naturalist 240 T.S. McCay, R.A. Pinder, E. Alvarado, and W.C. Hanson 2017 Vol. 24, No. 3 been collected in both acidic (pH < 5; Wherry 1924) and basic (pH > 8; James 1995) wetland soils, where animals are likely in direct, continuous contact with soil water. These findings suggest a breadth in pH tolerance that is unusual for lumbricid earthworms (Satchell 1955). Eisenoides lonnbergi has been collected in swamps, marshes, bogs, and along the banks of streams and rivers (e.g., Davies 1954, Gates 1935, Reynolds 2002). Thus, E. lonnbergi seems to exhibit broad habitat tolerances within wetland ecosystems. Knowledge of E. lonnbergi in the Northeast has come from just a few studies and relatively few sites. Gates (1972) regarded their presence in southern New England as likely the result of recent transportation by humans, and as recently as 2010 E. lonnbergi was documented at only a single site in New York State (Reynolds 2008, 2010; Schwert 1976). James (1995) summarized our understanding of the distribution of this species and indicated a distribution extending significantly into Massachusetts and New York. However, prior to the current work, the northernmost record for this species, in Oswego County, NY, was thought questionable because its location near a public fishing area made it a likely bait introduction (Schwert 1976). Ecological studies of earthworms in saturated soils have been less frequent than studies in upland habitats. Thus, the paucity of records for E. lonnbergi may be due to lack of scientific attention, an actual uncommonness, or both. The specific epithet for this species has been reported elsewhere as lönnbergi (e.g., Gates 1955) and loennbergi (Szlávecz and Csudi 2007). We report it here as lonnbergi (without the umlaut). Lonnbergi is a latinized Swedish surname (Lönnberg), and the International Code of Zoological Nomenclature (Article 32.5.2.1) specifies that diacritical marks should be removed from scientific names (International Commission on Zoological Nomenclature 1999). Because it is a Swedish, rather than German, surname, no “e” should be added after removal of the umlaut. We report here on new records of E. lonnbergi from wetlands and riparian habitats in New York State. These samples were taken well north of the southern limit of the last glacial advance, and several samples are farther north than all published records except the Oswego County, NY, sample of Schwert (1976). These new records shed additional light on the distribution, prevalence, and habitat associations of E. lonnbergi. Methods Sites and earthworm sampling We collected E. lonnbergi during a study of earthworms in riparian habitats of eastern New York State in 2006–2008 and during earthworm surveys of wetland habitats in central New York in June and July of 2016. Seven headwater streams were selected in each of Catskill State Park, Greene County, and Edmund Niles Huyck Preserve, Albany County. Additional information about these sites is available in Pinder (2013). During the summer of 2016, we sampled earthworms at 8 wetland habitats (bogs, fens, and swamps) in Madison and Chenango counties, New York, which were publically owned or owned by a land trust. Northeastern Naturalist Vol. 24, No. 3 T.S. McCay, R.A. Pinder, E. Alvarado, and W.C. Hanson 2017 241 Earthworms in wetlands can be difficult to detect due to the saturated soils of these habitats. Common techniques, such as mechanical (Springett 1981) or chemical (Lawrence and Bowers 2002) extraction, were not used to avoid damage to sensitive wetland environments. We used time-constrained searching, a technique commonly used to sample amphibians (Heyer et al. 1994), to sample earthworms. We spent a minimum of 2 person-hours of time in our efforts to find earthworms at each site. Structures at the soil surface, including rocks and logs, were flipped and then returned to their original position. When structures were not present, we manipulated the substrate by hand while looking for earthworms. We searched for animals under leaf litter and moss (if present) and within the underlying soils to a depth of about 10 cm. In sphagnum bogs, we would only minimally disrupt vegetation, instead spending most of our time watching the surface for signs of movement. At streamside sites we would systematically move along the stream bank searching for earthworms under rocks and logs. Because our sampling methods differed among habitats, we could not assume equal probability of detecting E. lonnbergi at all sites. Furthermore, weather likely influenced detection probabilities. Therefore, we avoided making inferences regarding the abundance of animals detected, and the described distribution should be viewed as conservative. Sampled earthworms were placed in plastic containers with substrate from the collection site and transported to the lab for processing. Environmental measurement At each location, we measured the pH of the substrate of sampled habitats. For habitats with free water at the surface (e.g., sphagnum bogs and fens), we would simply collect and measure the pH of free surface water. When surface water was not available, pH of the soil was measured using the method described in Carter (1993). We used a Bluelab® pH meter (Bluelab® Corporation Ltd., New Zealand) to measure pH. Processing of specimens We first examined collected worms alive, making notes about behavior and pigmentation, and photographed them when possible for later reference. Earthworms were euthanized in 10% isopropanol, fixed in 10% formalin for at least 48 hours, and then stored in 70% isopropanol. Processing was completed in 15-ml plastic centrifuge tubes, and earthworms were stored and labeled individually. We identified the earthworms by examination of external characters and use of Reynolds (1977) and Schwert (1990) and accessioned specimens into the oligochaete collection of the Museum of the Chenango Valley at Colgate University. Review of published and unpublished records We used literature databases (BioOne®, JSTOR®, Web of Sciencetm Core Collection) as aids in compiling published records of E. lonnbergi in Connecticut, Maryland, Massachusetts, New Jersey, New York, Pennsylvania, Rhode Island, and West Virginia. State-specific review articles by Reynolds (e.g., 2002) Northeastern Naturalist 242 T.S. McCay, R.A. Pinder, E. Alvarado, and W.C. Hanson 2017 Vol. 24, No. 3 provided a useful guide to the literature in these states. We attempted to find, without success, published records in Maine, New Hampshire, and Vermont. We searched the holdings of E. lonnbergi at the National Museum of Natural History (http://collections.nmnh.si.edu) and the Museum of Comparative Zoology at Harvard (http://mczbase.mcz.harvard.edu/). We additionally solicited unpublished records of E. lonnbergi from colleagues sampling earthworms in the Northeast. We did not confirm determinations for records that were not our own, and in one instance (Genesee County, NY, unpubl. record) we accepted an uncollected sighting of a specimen as a record. We estimated the geographic coordinates of each collection or sighting using the published description, field notes, or, if no specific information was available, the centroid of the county in which the specimen was collected. We recorded the habitat description indicated in the original account for each record and made particular note of any indication that the specimen(s) had been collected from soils that were saturated at the time of collection or other habitat or vegetation descriptors that would indicate collection from a wetland (e.g., “from sphagnum peat”). Collections made at the edge of a water body (e.g., “at edge of small pond”) were considered to have come from a wetland habitat. Results We collected E. lonnbergi from 14 new locations in New York State: 8 streamside sites, 3 bogs, and 3 forested wetlands (Table 1). All locations were glaciated during the last glacial maximum (Fig.1) and include the most northerly records for this species aside from the published record in Oswego County, NY (Schwert 1976). We found E. lonnbergi in 8 of 14 streamside sites (Pinder 2013) and 6 of 8 bogs, fens, and swamps. Our sites varied widely in pH (3.4 to 8.5), supporting claims that this species has a broad pH tolerance (e.g., James 1995). At our 3 most acidic sites (e.g., Fiddler’s Green Bog), E. lonnbergi apparently did not coexist with any other species (Table 1), suggesting that E. lonnbergi may be unique among earthworms of the Northeast in its tolerance of acidic saturated substrates. At riparian areas, E. lonnbergi was found with a wide variety of earthworm species (Table 1). Indeed, riparian habitats may support a uniquely diverse earthworm assemblage in the Northeast (Pinder 2013). At non-riparian habitats, E. lonnbergi was found with Allolobophora chlorotica (Savigny), Dendrobaena octaedra (Savigny), Eiseniella tetraedra (Savigny), Lumbricus rubellus Hoffmeister, and Octolasion tyrtaeum (Savigny). These species all have been found in a range of habitats, including environments that were either moist or acidic (or both), in previous studies (e.g., Zorn et al. 2008). We found 57 published records and 5 unpublished records of E. lonnbergi in Connecticut, Delaware, Massachusetts, Maryland, New Jersey, New York, Pennsylvania, Rhode Island, and West Virginia representing 62 distinct sites at which E. lonnbergi was collected (for detail of all records north of the southern limit of the last glacial maximum, see Supplemental File 1, available online at https://www. eaglehill.us/NENAonline/suppl-files/n24-3-N1544-McCay-s1, and, for BioOne Northeastern Naturalist Vol. 24, No. 3 T.S. McCay, R.A. Pinder, E. Alvarado, and W.C. Hanson 2017 243 Table 1. Sites at which we collected Eisenoides lonnbergi in New York State, along with a description of habitat and coexisting species identified. We measured pH of either free surface water, if any, or the soil at the site in which the species was found. Site name Habitat type pH Coexisting species Broadstreet Hollow, Catskill State Park (CSP), Riparian 5.2 (10) Aporrectodea caliginosa, A. limicola, A. rosea, Greene County A. tuberculata, Dendrobaena octaedra, Eiseniella tetraedra, Lumbricus rubellus, L. terrestris, Octolasion cyaneum, O. tyrtaeum Fiddler’s Green, Madison County Sphagnum bog 3.8 (0) Great Swamp Conservancy, Madison County Swamp 8.5 (2) Allolobophora chlorotica, L. rubellus Grevatt Road, Edmund Niles Huyck Preserve Riparian 6.0 (14) Aporrectodea caliginosa, A. limicola, A. rosea, (ENHP), Albany County A. trapezoides, A. tuberculata, Dendrobaena octaedra, Dendrodrilus rubidus, Eisenia fetida, Eiseniella tetraedra, L. castaneus, L. rubellus, L. terrestris, O. cyaneum, O. tyrtaeum Hunter Mountain, CSP, Greene County Riparian 4.4 (8) Aporrectodea trapezoides, A. rosea, A. tuberculata, Dendrobaena octaedra, Dendrodrillus rubidus, L. rubellus, O. cyaneum, O. tyrtaeum Jam Pond, Chenango County Sphagnum bog 3.6 (0) Lost Pond, Madison County Margin of sphagnum bog 4.6 (3) Dendrobaena octaedra, L. rubellus, O. tyrtaeum Mink Hollow, CSP, Greene County Riparian 4.4 (7) Aporrectodea tuberculata, A. rosea, A. turgida, Dendrobaena octaedra, Dendrodrillus rubidus, L. rubellus, O. tyrtaeum Nelson Swamp Unique Area, Madison County Forested fen 6.8 (3) Eiseniella tetraedra, L. rubellus, O. tyrtaeum North South Lake, CSP, Greene County Riparian 5.1 (9) Aporrectodea rosea, A. tuberculata, Dendrobaena octaedra, Dendrodrillus rubidus, Eiseniella tetraedra, D. octaedra, D. rubidus, L. rubellus, O. tyrtaeum Pond Trail, ENHP, Albany County Riparian 5.0 (11) Aporrectodea caliginosa, A. limicola, A. rosea, A. trapezoides, A. tuberculata, Dendrobaena octaedra, Dendrodrillus rubidus, Eiseniella tetraedra, L. rubellus, L. terrestris, O. tyrtaeum Route 42, CSP, Greene County Riparian 5.3 (8) Aporrectodea rosea, A. tuberculata, Dendrobaena octaedra, Dendrodrillus rubidus, Eiseniella tetraedra, L. rubellus, O. cyaneum, O. tyrtaeum Shooter, CSP, Greene County Riparian 5.5 (6) Aporrectodea tuberculata, Dendrobaena octaedra, Dendrodrillus rubidus, L. rubellus, O. cyaneum, O. tyrtaeum Stone Barn State Forest, Oneida County Swamp 3.4 (0) Northeastern Naturalist 244 T.S. McCay, R.A. Pinder, E. Alvarado, and W.C. Hanson 2017 Vol. 24, No. 3 subscribers, at https://dx.doi.org/10.1656/N1544.s1). Thirty-four of these records included detailed habitat or soils information. The large majority of records indicated a wetland habitat (30; 88%), with the largest number of collection sites characterized as riparian habitat (16; 47%), followed by swamps and marshes (9; 26%), lake-sides (4; 12%), and a bog (1; 3%). The 4 upland sites were all forested and included a Populus (aspen) forest (Schwert 1976), Pinus strobus L. (White Pine)–Tsuga (hemlock) forest (Gates 1935), and a mixed mid-Atlantic deciduous forest (Szlávecz and Csuzdi 2007, Szlávecz et al. 2011). In particular, E. lonnbergi is abundant and persistent at upland sites within the Smithsonian Environmental Research Center (SERC) in Maryland (Szlávecz and Csuzdi 2007). These SERC sites (Treefall, Triangle, and Weir; Yesilonis et al. 2016) have well-drained soils with a litter layer dominated by Liriodendron tulipifera L. (Tulip Poplar) and Fagus grandifolia Ehrh. (American Beech), indicating that at least certain populations of Figure 1. Locations at which Eisenoides lonnbergi were collected in the current study and in published and unpublished accounts. Shaded area was redrawn from the distribution described in James (1995) based on information available at that time. Line represents the southern limit of the Wisconsinan glaciation (Garrity and Soller 2009). Published records are plotted for Connecticut, Delaware, Massachusetts, Maryland, New Jersey, New York, Pennsylvania, Rhode Island, and West Virginia. Unpublished records in New York State were provided by A.M. Pagano and P.K. Ducey (State University of New York at Cortland, Cortland, NY) and S.W. James (University of Iowa, Iowa City, IA); unpublished record in Pennsylvania was provided by A.J. Britson (The Pennsylvania State University, State College, PA); unpublished records in Connecticut were provided by J.P. Fischer (White Memorial Conservation Center, Litchfield, CT). Northeastern Naturalist Vol. 24, No. 3 T.S. McCay, R.A. Pinder, E. Alvarado, and W.C. Hanson 2017 245 E. lonnbergi are physiologically tolerant of upland conditions (K. Szlávecz, Johns Hopkins University, Baltimore, MD, pers. comm.). Published accounts similarly mention wetland characteristics north of (13 of 16 sites) and south of (17 of 18 sites) the southern limit of the last glacial maximum. Thus, habitat selection seems similar in areas overwhelmingly dominated by exotic species and in areas with greater representation of nearctic earthworms. Discussion These new records underscore the prevalence of E. lonnbergi in the northern reaches of its described range and expand the known geographic distribution to the northwest. Importantly, these new records occur above the glacial margin. Many of these records occurred in remote habitats not adjacent to public fishing areas or other likely sources of recent human-aided colonization. We therefore argue that E. lonnbergi has naturally colonized Upstate New York following glacial retreat. The current limits to the geographic distribution of this species are unclear. Olson (1940), Eaton (1942), and Reynolds (2008) did not find Eisenoides at many collection sites in western and northern New York, but their sites were almost exclusively in upland habitats. So, the occurrence of E. lonnbergi farther to the north or west is still uncertain. This species has now been confirmed to exist in watersheds that drain northward, toward Lake Ontario, and earthworms may be passively dispersed by freshwater streams (Costello et al. 2011, Schwert and Dance 1979). Therefore, we predict that E. lonnbergi will be found at other locations in northern New York. Intentional sampling of wetland habitats will be necessary to clearly define the distribution of this species. Eisenoides lonnbergi was collected at over 60% of our sampled wetlands, suggesting that it may be relatively common in habitats with saturated soils in central and eastern New York. Nevertheless, this species is clearly uncommon in nonsaturated soils. In a study of 75 upland sites in southern Madison County, NY, we collected no E. lonnbergi (T. McCay, unpubl. data). Other studies of the earthworm faunas of upland habitats in New York have similarly detected no E. lonnbergi (Bernard et al. 2009, Stegman 1960). As reported previously (James 1995), our data indicate that E. lonnbergi is tolerant of very acidic conditions as well as neutral to slightly basic conditions. Satchell (1955) classified earthworms on the basis of pH tolerance and identified “ubiquitous” earthworms that were present in soils varying from pH 3.7 to pH 8.8. Eisenoides lonnbergi apparently exhibits a similarly broad range of pH tolerance. Its tolerance of acidic, saturated conditions may in fact be unique among earthworms in the Northeast. At our most acidic wetlands, we collected no other co-occurring species, including species identified by Satchell (1955) as ubiquitous and found in the region, such as Lumbricus rubellus. However, our sampling methodology was particularly aimed at E. lonnbergi and may have underrepresented other species, particularly Sparganophilus eiseni, which can be found at greater depths and in more saturated conditions than E. lonnbergi (Harman 1965, Pinder 2013). Eisenoides lonnbergi may possess an unusual physiological ability to Northeastern Naturalist 246 T.S. McCay, R.A. Pinder, E. Alvarado, and W.C. Hanson 2017 Vol. 24, No. 3 tolerate these saturated acidic conditions or, perhaps, it has an unusual ability to forage in these habitats dominated by Sphagnum mosses. Chang et al. (2016) used isotope analysis to demonstrate that E. lonnbergi occupied a distinctive trophic niche compared to other syntopic species. Additional research into the physiology and ecology of E. lonnbergi is necessary to resolve these uncertainties. Because it is so closely linked to wetland habitats and is among only a few representatives of the nearctic earthworm fauna in the Northeast, land managers may want to consider E. lonnbergi among other wetland endemics. In particular, E. lonnbergi may be the only oligochaete in acidic wetlands, such as bogs, a fact that may strengthen arguments for conservation based on the distinctiveness of these habitats. We encourage earthworm biologists to sample earthworms in nontraditional environments in northern North America. It is within marginal habitats (e.g., wetlands) and microhabitats (e.g., under bark) that northern native species are predominantly found (James 1995). Additional sampling is needed before we can construct an accurate understanding of the northern edge of the distribution of Eisenoides lonnbergi, and other native earthworms, in North America. Acknowledgments S.E. Scanga, S.E. Dexter, E.A. Hutto, A.O. Nugent, and V.C. Escobar provided help in the field and lab. Special thanks to A.J. Britson, P.K. Ducey, J.P. Fischer, S.W. James, and A.M. Pagano for sharing data regarding field collections of Eisenoides lonnbergi. We are grateful to the New York State Department of Environmental Conservation, the Southern Madison Heritage Trust, and the Cazenovia Preservation Foundation for allowing access to properties. The Upstate Institute at Colgate University provided funding in support of this project. The first and second authors contributed equally to this work Literature Cited Bernard, M.J., M.A. Neatrour, and T.S. McCay. 2009. 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