“…Freshwater mussels (Unionoida-hereafter "mussels") can serve as a model system to study ecological baselines as reference conditions, in part because they are among the most threatened freshwater fauna in North America (Haag, 2012;Strayer et al, 2004). There are several suggested causes for these declines, including habitat loss and destruction (Williams, Warren, Cummings, Harris, & Neves, 1993), dams (Haag, 2012;Layzer, Gordon, & Anderson, 1993;Vaughn & Taylor, 1999), invasive species (Baker & Hornbach, 2008;Sousa, Novais, Costa, & Strayer, 2014) and land-use change (Arbuckle & Downing, 2002;Atkinson, Julian, & Vaughn, 2014;Cao, Huang, & Cummings, 2013;Cao et al, 2015;Poole & Downing, 2004). However, few studies have determined specific causes of declines, and thus, long-term impacts are often identified as responsible for decreases in population density and assemblage diversity (Downing, Van Meter, & Woolnough, 2010;Strayer et al, 2004).…”