Lakewide dominance does not predict the potential for spread of dreissenids Vadim A. Karatayev a, ⁎, Alexander Y. Karatayev b,1 , Lyubov E. Burlakova b,c,1,2 , Dianna K. Padilla d,3 a Office of Undergraduate Biology, 216 Stimson Hall, Cornell University, Ithaca, NY 14853, USA b Great Lakes Center, Buffalo State College, Buffalo, NY 14222,USA c The Research Foundation of The State University of New York, Buffalo State College, Office of Sponsored Programs, Buffalo, NY 14222, USA d Department of Ecology and Evolution, Stony Brook University, Stony Brook, NY 11794-5245, USA abstract article info Article history: Received 18 March 2013 Accepted 29 August 2013 Available online xxxx Communicated by Michael Sierszen Index words: Dreissena polymorpha Dreissena rostriformis bugensis Vectors of spread Recreational boats Invasive species Great Lakes In recent years, quagga mussels (Dreissena rostriformis bugensis) have almost completely replaced zebra mussels (Dreissena polymorpha) in the Lower Great Lakes. As recreational boats are the main vector of spread for dreissenids in North America, this study examined whether lakes Erie and Ontario could still be sources for the spread of zebra mussels. In the summer–fall of 2010, the abundance of each species of Dreissena on 196 boats from 5 marinas in lakes Erie and Ontario was examined. Additional samples of Dreissena in 2010–2012 were col- lected in tributaries, bays, and in the upper littoral zones of these lakes. A total of 77 boats were fouled by Dreissena, and of those 61 were fouled by both species, 13 were fouled just by zebra mussels, and only 3 were fouled solely by quagga mussels. Although quagga mussels compose ~99% of dreissenids in eastern Lake Erie and in Lake Ontario, on boats at most marinas sampled, zebra mussels were usually more abundant and significantly larger than quagga mussels. Refugia for zebra mussels were found in bays, tributaries, and upper littoral zones with high wave activity. Thus, although quagga mussels are now more abundant than zebra mussels within the Lower Great Lakes, these waterbodies still have the potential to be a source for the spread of zebra mussels, and for some vectors, the propagule pressure from zebra mussels is likely greater than that from quagga mussels. © 2013 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved. Introduction Over the past century there has been an exponential increase in the transport of nonnative species, which then become of concern in the new aquatic habitats they invade (Leppäkoski and Olenin, 2000; Ruiz and Carlton, 2003). In North America, at least 182 nonnative species have been introduced to the Great Lakes over the last 150 years, more than any other freshwater system in North America (Ricciardi, 2006). Being the major port of entry for freshwater aquatic invaders, these waterbodies then act as a major source for their spread to inland waterbodies across North America (Padilla et al., 1996). Although some of these species may be closely related, the environmental and economic impacts, even for congeners, may differ (Karatayev et al., 2011, 2013). Therefore, contrasting congeners with different rates of spread at different spatial scales may be a useful tool for predicting which invaders will be more successful at spreading across space and time, especially for different vectors and mechanisms of spread (Karatayev et al., 2011, 2013). The zebra mussel (Dreissena polymorpha) and quagga mussel (Dreissena rostriformis bugensis) are among the most prominent aquatic invaders in North America. In Lake Erie, D. polymorpha was first discov- ered in 1986 (Carlton, 2008), and D. r. bugensis was first found in 1989 (Mills et al., 1993). Both species have planktonic larvae and an attached adult stage, representing a novel ecological type for North American freshwaters. They act as ecosystem engineers and have large ecological and economic impacts (reviewed in Karatayev et al., 1997, 2002, 2007; Nalepa and Schloesser, 1993; O'Neill, 2008). Although the importance of different vectors for the introduction and spread of dreissenids has varied widely over the last two centuries (reviewed in Karatayev et al., 2007, 2011), recreational boating is currently the major vector of spread from the initial site of introduction (Lake Erie) for these invaders in North America (Johnson and Carlton, 1996; Johnson and Padilla, 1996; Johnson et al., 2001, 2006; Padilla et al., 1996). Given the extensive use of the Great Lakes by recreational boaters, these waterbodies have become the major sources for the spread of Dreissena in the region. Initially, lakes Erie and Ontario were dominated by D. polymorpha, which achieved high densities in the littoral zones, while D. r. bugensis was found in the deep areas of the lakes (Dermott and Dow, 2008; Patterson et al., 2005; Watkins et al., 2007). However, in the mid- 1990s, the zebra mussel was displaced by quagga mussels, and by the mid-2000s quagga mussels composed N 90% of dreissenids in both lakes (Patterson et al., 2005; Pennuto et al., 2012; Watkins et al., Journal of Great Lakes Research xxx (2013) xxx–xxx ⁎ Corresponding author. Tel.: +1 716 834 0007. E-mail addresses: vak32@cornell.edu (V.A. Karatayev), karataay@buffalostate.edu (A.Y. Karatayev), burlakle@buffalostate.edu (L.E. Burlakova), padilla@life.bio.sunysb.edu (D.K. Padilla). 1 Tel.: +1 716 878 5432. 2 Tel.: +1 716 878 4504. 3 Tel.: +1 631 632 7434. JGLR-00618; No. of pages: 8; 4C: 0380-1330/$ – see front matter © 2013 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jglr.2013.09.007 Contents lists available at ScienceDirect Journal of Great Lakes Research journal homepage: www.elsevier.com/locate/jglr Please cite this article as: Karatayev, V.A., et al., Lakewide dominance does not predict the potential for spread of dreissenids, J Great Lakes Res (2013), http://dx.doi.org/10.1016/j.jglr.2013.09.007