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2 J. L. METCALF ET AL. (France & Collins 1993; Mingozzi & Esteve 1997; Beever et al. 2003; Sousa et al. 2010). In other cases, movement of individuals has expanded the distribution of species beyond their native range (Carlton 1996; McKinney & Lockwood 1999; Kowarik 2003). Sorting past and pres- ent patterns of diversity are further complicated by tra- ditional taxonomic treatments that may not accurately reflect phylogenetic diversity (Graham et al. 2004; Pfenninger & Schwenk 2007). Historical records docu- menting the actions that ultimately altered diversity and distribution provide one means of assessing the cause and magnitude of change (Westley & Fleming 2011) and reconstructing historical distributions of spe- cies (Franco & Morgan 2007; Gil- Sanchez & McCain 2011). Another way to estimate regional diversity and historical distributions, particularly for taxa plagued with taxonomic uncertainties, is to analyse genetic data from samples collected prior to human activities (e.g. Valentine et al. 2008; Hansen et al. 2009; Paplinska et al. 2011; Iwamoto et al. 2012). In concert, these two approaches can lead to an understanding of how actions by humans have changed the diversity and dis- tribution of species. This information is critical for establishing a baseline of historical conditions to guide restoration goals for species in decline or threatened with extinction. Our study focuses on a biological icon of the western United States, the cutthroat trout (Oncorhynchus clarkii). We know from historical records that native trout suf- fered widespread extirpations (Allendorf & Waples 1996; Dunham et al. 1997; Behnke 2002; Harig & Fausch 2002; Novinger & Rahel 2003; Young 2009; USFWS 2010), were propagated and moved across the landscape (Wiltzius 1985; Pister 2001; Dunham et al. 2004), and that the taxonomic record is rife with errors (Behnke 2002; Metcalf et al. 2007). Here, we evaluate hypotheses about the distribution and diversity of cutthroat trout across seven major drainages encompassing the Pacific and Atlantic slopes of the Continental Divide in the Southern Rocky Mountains, North America. The prevailing view of native diversity and distribution Historically, four distinct subspecies of cutthroat were described from Colorado (Fig. 1). The Colorado River cutthroat trout (O. c. pleuriticus) was described as native to all major drainages of the western slope of the Conti- nental Divide, including the San Juan, Gunnison, Colo- rado and Yampa River basins (Behnke 1992). The greenback cutthroat trout (O. c. stomias) was described from the Arkansas and South Platte basins east of the Continental Divide (Jordan 1891; Behnke 2002). The Rio Grande cutthroat trout (O. c. virginalis) was documented from the Pecos, Canadian and Rio Grande Rivers on the east slope of the Continental Divide (Behnke 1992). The fourth taxon, the Yellowfin cutthroat trout (O. c. macdonaldi), was restricted to Twin Lakes in the headwaters of the Arkansas River (Jordan 1891; Behnke 1992). Both O. c. macdonaldi and O. c. stomias were declared extinct at one time (Behnke 1992), although the greenback cutthroat trout was purportedly rediscovered in the 1950s —an event that initiated a large -scale resto- ration effort aimed at re- establishing the subspecies to a large number of tributaries in both the South Platte and Arkansas river basins (Behnke 1969; Young & Harig 2001). A published phylogenetic inference based on mitochondrial DNA (mtDNA) revealed four divergent lineages, which were additionally supported by cluster- ing methods using both microsatellite and AFLP nuclear markers (Fig. 2) (Metcalf et al. 2007; Pritchard et al. 2009). While the number of taxa aligned with the prevailing view of cutthroat trout diversity in the Southern Rockies, the geographical distribution of sub- species did not. In fact, trout putatively identified as O. c. stomias and O. c. pleuriticus were found in streams and lakes on both slopes of the Continental Divide, a pattern interpreted as an effect of fish stocking (Metcalf et al. 2007). In addition, a fourth, divergent lineage was discovered, but it was only found in a single stream (Bear Creek) in the Arkansas River drainage. Whether this lineage represented a named subspecies, such as O. c. stomias or the extinct O. c. macdonaldi, could not be determined without understanding past diversity and the influence of stocking on the distribution of subspe- cies. These findings called into question the current tax- onomy of cutthroat trout and prompted a thorough investigation into the potential effects of past stocking and propagation on the current diversity and distribu- tion of cutthroat trout. Extirpation and propagation effects Review of historical records indicated that native trout populations in Colorado suffered dramatic declines beginning in the middle 1800s. Initially, trout popula- tions were decimated by overfishing, mining pollution and agricultural practices (Supporting information; Young & Harig 2001). Coincidentally, a number of pri- vate individuals, and later, state and federal agencies, began propagating trout for commercial and recrea- tional purposes (Wiltzius 1985). The first documented movement of native trout within the state occurred in 1873 (Miner July 8th, 1873). Although our research through the public records does not provide a complete account of the propagation and stocking activities by private citizens, what is clear from the newspaper © 2012 Blackwell Publishing Ltd