Continuation of the Survey on Nantucket, Tuckernuck, and Muskeget Islands, Massachusetts

Andrew Mckenna-Foster and Julianna Arntzen Maria Mitchell Association, 4 Vestal St., Nantucket, MA, 02554

ABSTRACT

We collected on Nantucket, Tuckernuck, and Muskeget Islands, MA using a modified liquid mustard extraction method. We found earthworms on all three islands and added 54 specimens to the collection. We identified a new island record () and the species list now contains six species. rubidus and Dendrobaena octaedra are the most common species numerically. Some areas of Nantucket appear to have no earthworms, but we predict they will be eventually colonized by litter dwelling species.

INTRODUCTION

In 2008, we surveyed Nantucket and Tuckernuck Islands for earthworm species and we found five non-native species (Arntzen and Mckenna-Foster, 2008). In 2009, we continued our surveying to include more habitat types and we focused our collecting in September and October to maximize the chances of catching adult worms. Our objectives were to focus on areas where worms were likely to be found on Nantucket (near human development) and initiate collecting on Muskeget Island.

METHODS

We used a liquid earthworm extraction method established by Bouche and Gardner (1984), Lawrence and Bowers (2002) and Hale et al. (2005). At each site a plastic ring is driven into the ground (~5 cm) with the aid of a shovel to isolate a 0.15 m2 patch of ground. We slightly modified the methodology from Hale et al. (2005) by using a circular plastic divider rather than a square metal one (Fig 1). Leaf litter within the ring is searched for surface dwelling earthworms and then cleared from the ring to increase the visibility of the soil. A liquid solution of 40g yellow mustard powder to 1 gallon water is then poured into the ring. The mustard irritates the worms, which come to the surface and are easily collected. In all samples, we poured half of the solution into the ring and waited five minutes before pouring in the second half for a total sample time of 10 minutes.

Figure 1.Top pictures: Molly Hukari pouring mustard water into plastic ring (left), looking into a plastic ring that has been cleared of vegetation and soaked in mustard water (right). Bottom pictures: Dendrodrilus rubidus emerging after the addition of mustard water on Muskeget (left) and Aporrectodea sp. emerging at Windswept Cranberry Bog on Nantucket (right). Photos: Mckenna-Foster

We estimated the ash free dry mass of worm species using allometric equations (Hale et al. 2004). We used an equation that provides accurate biomass prediction for worms in the genera Lumbricus, Aporrectodea, and Dendrobaena:

RESULTS

Earthworms survive on all three islands (Fig. 2). We completed 15 additional earthworm surveys in 2009 using mustard extraction and added one new species to the species list (Table 1). Seven extractions were completed on Nantucket, three on Tuckernuck, and five on Muskeget (Table 2). We also collected one earthworm casually from private property on Nantucket. This is the first time earthworms have been collected on Muskeget. We added 42 earthworms to the Nantucket collection, two earthworms to the Tuckernuck collection, and started the Muskeget collection with 10 earthworms.

Figure 2. Sample locations on Nantucket, Tuckernuck, and Muskeget Islands for 2008 and 2009. Black circles indicate sites where earthworms (juvenile and/or adults) were found and white circles indicate sites where no earthworms were found.

Dendrodrilus rubidus is the only species found on all three islands (see Appendix) and is the most common species in the collection with 88 specimens. Many of the unidentifiable juvenile worms looked to be D. rubidus as well. Dendrobaena octaedra is the second most common species with 27 specimens and is found on both Nantucket and Tuckernuck. The Appendix contains range maps for all species.

Table 1. Earthworm species found on Nantucket, Tuckernuck, and Muskeget Islands. Average lengths were calculated from specimens in this study. *Added to the list in 2009. Species Ecological Category Origin Avg. Length (mm) Local Range Amynthas sp. Epi-endogeic (surface dwelling) Asia 59 Aporrectodea caliginosa Endogeic (Soil Dwelling) 70 Dendrobaena octaedra Epigeic (Litter) Europe 20 See Appendix Dendrodrilus rubidus Epigeic (Litter) Europe 22 Lumbricus rubellus * Endogeic (Soil Dwelling) Europe 52 Anecic (Burrowing) Europe 36

Table 2. Sampling information and the number of worms captured at sites sampled on Nantucket, Tuckernuck, and Muskeget Islands. Location Coordinates Coll. Dates Collection Method Earthworm species (# Ash free specimens) dry mass per m2 NANTUCKET Coskata Woods NBI Plot N41.34740 31July2008 Mustard Extraction (1) Dendrodrilus rubidus (70) 0.326 W70.01575 20Aug2008 Mustard Extraction (5) Eel Point Dunes N41.29346 29Sept2009 Mustard Extraction (1) None Found 0 W70.19247 Eel Point Parking Area N41.29141 29Sept2009 Mustard Extraction (1) Dendrobaena octaedra (10) W70.19267 Lumbricus terrestris (1) 2.14 Lumbricus rubellus (1) Lumbricus sp. (4 Juvenile) Madequecham Valley NBI N41.25422 4Sept2008 Mustard Extraction (5) None Found 0 Plot W70.04819 Mass. Audubon NBI Plot N41.27608 27Aug2008 Mustard Extraction (5) None Found 0 W69.98953 2Oct2009 Mustard Extraction (2) Smooth Hummocks Coastal N41.25116 3Sept2008 Mustard Extraction (5) Dendrodrilus rubidus (2) 0.011 Preserve NBI Plot W70.11880 Smooth Hummocks Coastal N41.25116 27May2008 Casual Collection Aporrectodea caliginosa (1) (No Area) Preserve Area W70.11880 Pitfall Trap Dendrobaena octaedra (1) Squam Farm N41.30724 23Aug2009 Mustard Extraction (2) Dendrobaena octaedra (3) W69.99974 Lumbricus sp. (2 Juvenile) 0.352 Casual in leaf litter Dendrobaena octaedra (1) Squam Swamp NBI Plot N41.31858 26July2008 Leaf Litter Search Amynthas sp. (8) 0.075 W70.00285 16Aug2008 Mustard Extraction (5) Dendrodrilus rubidus (12) Windswept Cran. Bog N41.29846 2Oct2009 Mustard Extraction (1) Aporrectodea sp. (3 W70.00475 immature) Dendrobaena octaedra (10) 2.55 Lumbricus rubellus (4) Lumbricus sp. (2 Juvenile) 6 Blue Heron Rd. N41.28451 29Sept2009 Casual Amynthas sp. (1) (No Area) Nantucket W70.18380 Maria Mitchell Natural N41.280312 01June2008 Casual Collection Lumbricus terrestris (1 Science Museum Garden W70.104060 11July2008 adult) 0.972 Lumbricus sp. (3 Juvenile) Mid Island Fuel (tackle N41.272113 20Aug2008 Purchased Lumbricus terrestris (12) (No Area) shop/gas station) W70.093871 TUCKERNUCK Brown Property N41.30473 18July2008 Mustard Extraction (1) Dendrodrilus rubidus (1) 0.064 W70.26743 Fire House N.41.30438 18July2008 Mustard Extraction (5) Dendrobaena octaedra (2) 0.033 W70.26060 Dendrodrilus rubidus (2) Near Eastern Pond N41.301471 5June2008 Casual Collection Aporrectodea sp. (1) (No Area) W70.249588 TLT Field Sta. N41.30187 14-15 Oct Mustard Extraction (3) Juvenile (2) - W70.25460 2009 MUSKEGET Southeast Cabin N41.33321 5Sept2009 Mustard Extraction (2) Dendrodrilus rubidus (1) 0.064 W.70.29495 Juvenile (3) South Middle Creek N41.33347 5Sept2009 Mustard Extraction (2) Juvenile (6) - W70.29735 North Middle Creek N41.33425 5Sept2009 Mustard Extraction (1) None Found - W70.29720

DISCUSSION

Earthworms appear to be widespread across Nantucket, Tuckernuck, and Muskeget. Colonization by European settlers is the most likely explanation for this wide distribution in what was most likely a wormless area historically. Our sampling efforts in the Eastern Moors (Mass. Audubon NBI Plot) and the Madequecham Valley have produced no earthworms suggesting that these areas are either inhospitable to earthworms, or that earthworms have not yet been introduced. We hypothesize that earthworms will eventually either be introduced or will disperse into these areas. The presence of Dendrodrilus rubidus in the Smooth Hummocks Coastal Preserve indicates that this species can survive in the leaf litter of relatively intact sandplain grassland and coastal heathland habitat.

We found no earthworms in the dunes of Eel Point. However, thick mats of leaf litter occur under the thicker vegetation and could potentially support epigeic species.

The most widespread and the most common species numerically, Dendrodrilus rubidus and Dendrobaena octaedra, are both litter dwelling. The soils on the islands are probably too sandy to support the soil dwelling species other than in areas where richer soil has been created by humans (e.g. gardens and old agricultural land).

We will continue collecting earthworms. Specimens will be sent to the Museum of Comparative Zoology, Cambridge, MA and a synoptic series will be stored at the Maria Mitchell Natural Science Museum, Nantucket, MA.

ACKNOWLEDGMENTS

This project was funded by a 2008 grant from the Nantucket Biodiversity Initiative. We thank the Massachusetts Audubon Society, the Nantucket Land Bank, the Nantucket Conservation Foundation, the Tuckernuck Land Trust, Tuckernuck residents, and Daniel Drake for letting us collect on their properties. Cheryl Beaton, Molly Hukari, Jennifer Goyette, Nancy Mckenna, Meredith Steck, and Jonathan Shuster kindly helped with fieldwork.

LITERATURE CITED

Bouche, M.B. and R.H. Gardner. 1984. Earthworm functions: population estimation techniques. Revue d’Ecologie et de Biologie du Sol 21:37-63.

Hale, C.M., L.E. Frelich, and P.B. Reich. 2004. Allometric equations for estimation of ash-free dry mass from length measurements for selected European earthworm species () in the western Great Lakes region. American Midland Naturalist 151: 175- 185.

Hale, C.M., L.E Frelich, and P.B. Reich. 2005. Exotic European earthworm invasion dynamics in northern hardwood forests of Minnesota, USA. Ecological Applications 15(3):848-860. Lawrence, A.P. and M.A. Bowers. 2002. A test of the ‘hot’ mustard extraction method of sampling earthworms. Soil Biology and Biochemistry 34:549-552.

APPENDIX