Regional Studies in Marine Science 34 (2020) 101049 Contents lists available at ScienceDirect Regional Studies in Marine Science journal homepage: www.elsevier.com/locate/rsma Reconstructing the distribution of the non-native sea anemone, Diadumene lineata (Actiniaria), in the Canadian Maritimes: Local extinction in New Brunswick and no regional range expansion in Nova Scotia since its initial detection Kevin C.K. Ma a,b,∗ , Heather E. Glon c , Heather L. Hawk a , Cody N. Chapman d a Québec-Océan, Département de biologie, Université Laval, Québec, Québec, G1V 0A6, Canada b Department of Zoology and Entomology, Rhodes University, Grahamstown, 6139, Eastern Cape, South Africa c Museum of Biological Diversity, Department of Evolution, Ecology, and Organismal Biology, The Ohio State University, Columbus, OH, 43212, United States of America d Department of Plant, Food, and Environmental Sciences, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada article info Article history: Received 27 September 2019 Received in revised form 5 December 2019 Accepted 5 January 2020 Available online 7 January 2020 Keywords: Biological invasion Invasive species Actiniarians Anthozoans Monitoring Atlantic Canada abstract Since its first observations in New Brunswick (Sam Orr’s Pond) and Nova Scotia (Bedford Institute of Oceanography in Dartmouth) in 2009 and 2013, respectively, Diadumene lineata has been observed spreading to new locations in the Canadian Maritimes. In 2017 and 2018, regional surveys for non- native species did not detect D. lineata in New Brunswick, suggesting local extinction. Recent surveys also did not detect D. lineata in Prince Edward Island. However, between 2013 and 2018, D. lineata was detected in Nova Scotia (in chronological order) from Lunenburg Harbour (Lunenburg), Hermans Island (Lunenburg), Black Rock Beach (Halifax), Oak Island Marina (Chester), and Dartmouth Yacht Club (Dartmouth). These new observations combine to reconstruct the known recent distribution of this non-native sea anemone in the Canadian Maritimes. Further, after five years since its first detection in Nova Scotia, the regional distribution of D. lineata remained unchanged, restricted to a region of approximately 100 km between Halifax and Lunenburg. Although the primary focus is on D. lineata, additional records of the non-native macroalga, Codium fragile, from Sam Orr’s Pond and the native sea anemone, Metridium senile, fouling dock structures throughout the Canadian Maritimes are included in this report as M. senile commonly overlaps in habitat with D. lineata. © 2020 Elsevier B.V. All rights reserved. 1. Introduction The orange-striped green sea anemone, Diadumene lineata (Verrill, 1869), is an infralittoral species considered to be native to China and Japan, where it was first described (Verrill, 1869; Uchida, 1932). It is now known as one of the most widely distributed sea anemones in the world, as it has been introduced via a variety of ways, including (a) the translocation of fouled boat hulls, bivalve aquaculture products, and aquaculture equipment, (b) ballast water exchange, and (c) long-distance rafting on an- thropogenic debris (Verrill, 1898; Shick, 1976; Shick and Lamb, 1977; Gollasch and Riemann-Zürneck, 1996; Carlton et al., 2017). Diadumene lineata is a relatively small, solitary sea anemone with a maximum diameter of up to 22 mm at the base, although ∗ Corresponding author at: Department of Zoology and Entomology, Rhodes University, Grahamstown, 6139, Eastern Cape, South Africa. E-mail addresses: k.ma@ru.ac.za (K.C.K. Ma), Glon.2@osu.edu (H.E. Glon), heather.hawk.1@ulaval.ca (H.L. Hawk), cd430265@dal.ca (C.N. Chapman). bodies ranging from 5 to 10 mm in diameter are typically en- countered (Uchida, 1932; Hand, 1955; Fautin and Hand, 2007; Fautin et al., 2009). The smooth columnar body is greyish-green in colour with thin, orange or white longitudinal stripes (Uchida, 1932; Hand, 1955). In its native range, up to four colour morphs have been described, which vary in stripe size, colour, and ar- rangement (Uchida, 1936; Ryan and Kubota, 2016). Tentacles are slender and typically number about 25 but can be as many as 100 (Carlgren and Hedgepeth, 1952; Fautin and Hand, 2007). In- dividuals expel defensive acontia when disturbed (Uchida, 1932). A native congener, Diadumene leucolena (Verrill, 1866) is known from the Canadian Maritimes (Thomas et al., 1983); it can be distinguished from D. lineata by its transparent or pinkish body, large cinclides, and the absence of coloured stripes on the body column. Diadumene lineata inhabits marine and estuarine environ- ments tolerating a wide range of salinities (5 to 35 psu) and water temperatures (0 to 27.5 ◦ C), which contributes to its status as a global invader (Shick, 1976; Seaton, 1985; Konecny and Harley, https://doi.org/10.1016/j.rsma.2020.101049 2352-4855/© 2020 Elsevier B.V. All rights reserved.