GRSM_BROOK_TROUT_GENETICS (FeatureServer)

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Service Description: These data depict the locations (only) of all Brook Trout Genetics study sites in the park. Great Smoky Mountains National Park (GRSM) is committed to monitoring ecological and evolutionary functions and processes of park ecosystems. Brook trout (Salvelinus fontinalis) is the only salmonid native to the Southern Appalachians and functions as a keystone species in some headwater streams. The historic use of hatchery-reared brook trout for supplemental and restorative stocking in GRSM underscores the need to recognize the evolutionary relationship among stream populations. A recent survey of microsatellite DNA variation in GRSM brook trout indicated the presence of highly significant differentiation at all hieratical levels which suggests that the individual stream should be considered the unit of management. Given that management resources are limited and that stream-specific management is often not practical, fisheries managers need to know whether the genetic divergence observed among GRSM brook trout reflect adaptive differences or is the variation due to stochastic processes like random genetic drift. DNA microarrays are a powerful method for the global analysis of steady-state intracellular mRNA levels, and thus identifying genes that are transcriptionally modulated as a consequence of metabolic or bioenergetic demands. The information gathered from these arrays of gene sequences can be used to characterize complex biological processes and interactions providing insight into the adaptive significance of observed genetic differentiation. This research objective, if funded, would represent the first attempt at determining whether GRSM fisheries managers should focus their resources on genetic relatedness or demographics.Brook trout (Salvelinus fontinalis) is the only trout native to the Southern Appalachians. Since the turn of the century, this native trout has lost approximately 75 percent of its range in Great Smoky Mountains National Park (GRSM) (Kelly et al. 1980). Initial range loss (about 50 percent) has been attributed to logging and resultant water quality degradation (King 1937). This activity virtually eliminated brook trout in streams below about 914 m (3,000 ft) in elevation. In turn, residents and loggers became concerned because they had nothing for which to fish. To meet the demand for recreational angling at the time (around 1910), logging companies began stocking both non-native rainbow trout and northern brook trout and continued this activity until the Park was established in 1934. The Park continued to allow the stocking of both species until 1974.Park staff in the 1930s and 1940s saw no harm in stocking rainbows and believed that as reforestation occurred, brook trout would reclaim lost range (King, personal communication). However, distribution surveys in the 1970s showed this not to be true and that 45 percent of the range exclusively occupied by brook trout had been lost since the mid-1930s (Kelly et al. 1980). The decline in allopatric brook trout range was the direct result of rainbow trout encroachment into previously unstocked brook trout streams (Larson and Moore 1985). Native brook trout had become restricted to marginal headwater streams above 1,067 m (3,500 ft), characterized by steep gradients and pH that is naturally slightly acidic. Based on the report by Kelly et al. (1980) it was determined that the only places brook trout could not be displaced are in streams above waterfalls where rainbows could not ascend.Historically, local residents were very vocal about introduced northern strains of brook trout being different from the native brook trout or "speckled trout." Studies in the 1950s showed that physical differences do exist between Southern Appalachian brook trout and hatchery fish. In 1993, a study conducted by the University of Tennessee provided conclusive evidence that Southern Appalachian brook trout are genetically distinct at the subspecies level from northern populations (McCracken et al. 1993). This effort collected brook trout from 47 streams across the Park and demonstrated that brook trout in 36 (64%) were pure Southern Appalachian brook trout. Fish from two streams were northern brook trout and the others were hybrids. The report recommends that everything possible be done to protect Southern Appalachian brook trout.Parkwide water quality monitoring was initiated in 1992 as part of the Inventory and Monitoring program. Data from this program clearly show that stream acidity increases with increasing elevation (Robinson et.al. 2001). Models developed by these authors indicate that if current trends for pH continue that in four years that streams above 1,067m (3,500 ft.) will have a pH of 6.0 and in 15 years the pH will be 5.5 this eliminating brook trout and other aquatic species from these stream segments. Brook trout distribution monitoring in the 1990’s has documented headwater range loss in six streams that had brook trout in previous surveys. All losses have been in streams at or above 1,067m and field pH measurements indicate the streams are to acidic to support fish life. These data increase the urgency of restoring stream segments identified in the Park’s Fishery Management Plan for this native trout as rapidly as possible to provide a long-term refuge for native brook trout.GRSM is committed to developing systematic approaches to inventorying composition and monitoring functions and processes of park ecosystems. The historic use of hatchery-reared brook trout for supplemental stocking in almost every watershed of GRSM and the potential negative impacts to the overall health and long-term maintenance of populations resulting from this approach underscore the need to recognize the lineage of each population. Increased interest in restoring native southern Appalachian brook trout to selected streams in GRSM requires a better understanding of the distribution of native, introduced northern strain, and their hybrids. While genetic surveys have been conducted in selected streams within GRSM, numerous streams remain to be typed to major evolutionary lineage (i.e., southern Appalachian, northern). Knowledge from these surveys should be incorporated into all management efforts to identify unique genetic diversity and to prevent the potential deleterious effects associated with introduction and translocation of maladapted fish. Ecological and evolutionary effects associated with introducing nonnative hatchery strains have been documented for other salmonid species (Ferguson 1990; Allendorf 1991; Evans and Willox 1991; Krueger and May 1991). Potential problems associated with the mixing of genetically divergent stocks of brook trout include the loss of local adaptations, disruption of locally-adapted gene combinations (i.e., outbreeding depression), and the spread of pathogens. Declines in numbers of breeding individuals in populations can result in reduced levels of genetic diversity among wild brook trout populations (e.g., through genetic drift). Moreover, moderate levels of genetic divergence have been documented at local and regional levels, which suggests that extirpation of local populations has likely led to the irretrievable loss of evolutionarily significant lineages. Relatively large genetic differences can occur over short geographic distances among stream-dwelling brook trout populations (McCracken et al. 1993; Perkins et al. 1993); therefore, transplantations of fish may create undesirable effects.Surveys of genetic variation among brook trout populations have focused on (1) nuclear DNA variation in the form of protein differences or polymorphisms (i.e., allozymes) and (2) cytoplasmic DNA sequence variation in the rapidly evolving, maternally-inherited mitochondrial (mt) DNA. Allozyme studies have demonstrated that some genetic variation still exists among extant inland brook trout populations (Perkins et al. 1993; Kriegler et al. 1995) and that barriers to gene flow primarily existed among brook trout originating in distinct regional river systems (Stoneking et al. 1981; McCracken et al. 1993). Comparisons of mtDNA diversity between brook trout from putative refugial and recolonization zones indicated that large phylogeographic differences were found between northern and southern populations, that collections outside the zone of glaciation were the most genetically heterogeneous, and that multiple refugia contributed to northern recolonization after glacial retreat (Danzmann et al. 1998). [Stan: Insert a couple of sentences summarizing the allozyme results from Guffey et al. for GRSM. Perhaps a sentence summarizing the results from Danzmann et al. 1998]Allozyme and mtDNA techniques have identified significant, genetic differentiation on a regional scale among brook trout; however, neither technique has detected sufficient levels of polymorphism to allow fine-scale resolution of local sub-population or metapopulation structure (i.e., isolation or high levels of gene flow). Recent studies have shown that microsatellite DNA variation affords the highest resolution of population structure of any technique brought to bear on fish species to date and suggest that in many instances the population unit functions at a finer-scale than the river (Beacham and Dempson 1998; Garant et al. 2000; Spidle et al. In Review). Following the discovery of microsatellite DNA markers over a decade ago (Tautz 1989), thousands of these loci have been described in eukaryotic organisms, including brook trout (Angers et al. 1995; two viable markers). Microsatellite DNA assays permit determination of the magnitude of genetic variation and diversity at the individual and population levels from the perspective of a more highly mutable set of markers. Due to the tendency for hypervariability and because only small amounts of tissue (often taken nondestructively) are required for genotyping, microsatellite DNA markers have supplanted allozymes in recent years as the genetic markers of choice for many management and biological problems including genetic stock identification, parentage assignment, forensics, and genome mapping (Schlötterer and Pemberton 1994; Jarne and Lagoda 1996, Goldstein and Schlötterer 1999).

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BROOK_TROUT_GENETICS (1)

Description: These data depict the locations (only) of all Brook Trout Genetics study sites in the park. Great Smoky Mountains National Park (GRSM) is committed to monitoring ecological and evolutionary functions and processes of park ecosystems. Brook trout (Salvelinus fontinalis) is the only salmonid native to the Southern Appalachians and functions as a keystone species in some headwater streams. The historic use of hatchery-reared brook trout for supplemental and restorative stocking in GRSM underscores the need to recognize the evolutionary relationship among stream populations. A recent survey of microsatellite DNA variation in GRSM brook trout indicated the presence of highly significant differentiation at all hieratical levels which suggests that the individual stream should be considered the unit of management. Given that management resources are limited and that stream-specific management is often not practical, fisheries managers need to know whether the genetic divergence observed among GRSM brook trout reflect adaptive differences or is the variation due to stochastic processes like random genetic drift. DNA microarrays are a powerful method for the global analysis of steady-state intracellular mRNA levels, and thus identifying genes that are transcriptionally modulated as a consequence of metabolic or bioenergetic demands. The information gathered from these arrays of gene sequences can be used to characterize complex biological processes and interactions providing insight into the adaptive significance of observed genetic differentiation. This research objective, if funded, would represent the first attempt at determining whether GRSM fisheries managers should focus their resources on genetic relatedness or demographics.Brook trout (Salvelinus fontinalis) is the only trout native to the Southern Appalachians. Since the turn of the century, this native trout has lost approximately 75 percent of its range in Great Smoky Mountains National Park (GRSM) (Kelly et al. 1980). Initial range loss (about 50 percent) has been attributed to logging and resultant water quality degradation (King 1937). This activity virtually eliminated brook trout in streams below about 914 m (3,000 ft) in elevation. In turn, residents and loggers became concerned because they had nothing for which to fish. To meet the demand for recreational angling at the time (around 1910), logging companies began stocking both non-native rainbow trout and northern brook trout and continued this activity until the Park was established in 1934. The Park continued to allow the stocking of both species until 1974.Park staff in the 1930s and 1940s saw no harm in stocking rainbows and believed that as reforestation occurred, brook trout would reclaim lost range (King, personal communication). However, distribution surveys in the 1970s showed this not to be true and that 45 percent of the range exclusively occupied by brook trout had been lost since the mid-1930s (Kelly et al. 1980). The decline in allopatric brook trout range was the direct result of rainbow trout encroachment into previously unstocked brook trout streams (Larson and Moore 1985). Native brook trout had become restricted to marginal headwater streams above 1,067 m (3,500 ft), characterized by steep gradients and pH that is naturally slightly acidic. Based on the report by Kelly et al. (1980) it was determined that the only places brook trout could not be displaced are in streams above waterfalls where rainbows could not ascend.Historically, local residents were very vocal about introduced northern strains of brook trout being different from the native brook trout or "speckled trout." Studies in the 1950s showed that physical differences do exist between Southern Appalachian brook trout and hatchery fish. In 1993, a study conducted by the University of Tennessee provided conclusive evidence that Southern Appalachian brook trout are genetically distinct at the subspecies level from northern populations (McCracken et al. 1993). This effort collected brook trout from 47 streams across the Park and demonstrated that brook trout in 36 (64%) were pure Southern Appalachian brook trout. Fish from two streams were northern brook trout and the others were hybrids. The report recommends that everything possible be done to protect Southern Appalachian brook trout.Parkwide water quality monitoring was initiated in 1992 as part of the Inventory and Monitoring program. Data from this program clearly show that stream acidity increases with increasing elevation (Robinson et.al. 2001). Models developed by these authors indicate that if current trends for pH continue that in four years that streams above 1,067m (3,500 ft.) will have a pH of 6.0 and in 15 years the pH will be 5.5 this eliminating brook trout and other aquatic species from these stream segments. Brook trout distribution monitoring in the 1990’s has documented headwater range loss in six streams that had brook trout in previous surveys. All losses have been in streams at or above 1,067m and field pH measurements indicate the streams are to acidic to support fish life. These data increase the urgency of restoring stream segments identified in the Park’s Fishery Management Plan for this native trout as rapidly as possible to provide a long-term refuge for native brook trout.GRSM is committed to developing systematic approaches to inventorying composition and monitoring functions and processes of park ecosystems. The historic use of hatchery-reared brook trout for supplemental stocking in almost every watershed of GRSM and the potential negative impacts to the overall health and long-term maintenance of populations resulting from this approach underscore the need to recognize the lineage of each population. Increased interest in restoring native southern Appalachian brook trout to selected streams in GRSM requires a better understanding of the distribution of native, introduced northern strain, and their hybrids. While genetic surveys have been conducted in selected streams within GRSM, numerous streams remain to be typed to major evolutionary lineage (i.e., southern Appalachian, northern). Knowledge from these surveys should be incorporated into all management efforts to identify unique genetic diversity and to prevent the potential deleterious effects associated with introduction and translocation of maladapted fish. Ecological and evolutionary effects associated with introducing nonnative hatchery strains have been documented for other salmonid species (Ferguson 1990; Allendorf 1991; Evans and Willox 1991; Krueger and May 1991). Potential problems associated with the mixing of genetically divergent stocks of brook trout include the loss of local adaptations, disruption of locally-adapted gene combinations (i.e., outbreeding depression), and the spread of pathogens. Declines in numbers of breeding individuals in populations can result in reduced levels of genetic diversity among wild brook trout populations (e.g., through genetic drift). Moreover, moderate levels of genetic divergence have been documented at local and regional levels, which suggests that extirpation of local populations has likely led to the irretrievable loss of evolutionarily significant lineages. Relatively large genetic differences can occur over short geographic distances among stream-dwelling brook trout populations (McCracken et al. 1993; Perkins et al. 1993); therefore, transplantations of fish may create undesirable effects.Surveys of genetic variation among brook trout populations have focused on (1) nuclear DNA variation in the form of protein differences or polymorphisms (i.e., allozymes) and (2) cytoplasmic DNA sequence variation in the rapidly evolving, maternally-inherited mitochondrial (mt) DNA. Allozyme studies have demonstrated that some genetic variation still exists among extant inland brook trout populations (Perkins et al. 1993; Kriegler et al. 1995) and that barriers to gene flow primarily existed among brook trout originating in distinct regional river systems (Stoneking et al. 1981; McCracken et al. 1993). Comparisons of mtDNA diversity between brook trout from putative refugial and recolonization zones indicated that large phylogeographic differences were found between northern and southern populations, that collections outside the zone of glaciation were the most genetically heterogeneous, and that multiple refugia contributed to northern recolonization after glacial retreat (Danzmann et al. 1998). [Stan: Insert a couple of sentences summarizing the allozyme results from Guffey et al. for GRSM. Perhaps a sentence summarizing the results from Danzmann et al. 1998]Allozyme and mtDNA techniques have identified significant, genetic differentiation on a regional scale among brook trout; however, neither technique has detected sufficient levels of polymorphism to allow fine-scale resolution of local sub-population or metapopulation structure (i.e., isolation or high levels of gene flow). Recent studies have shown that microsatellite DNA variation affords the highest resolution of population structure of any technique brought to bear on fish species to date and suggest that in many instances the population unit functions at a finer-scale than the river (Beacham and Dempson 1998; Garant et al. 2000; Spidle et al. In Review). Following the discovery of microsatellite DNA markers over a decade ago (Tautz 1989), thousands of these loci have been described in eukaryotic organisms, including brook trout (Angers et al. 1995; two viable markers). Microsatellite DNA assays permit determination of the magnitude of genetic variation and diversity at the individual and population levels from the perspective of a more highly mutable set of markers. Due to the tendency for hypervariability and because only small amounts of tissue (often taken nondestructively) are required for genotyping, microsatellite DNA markers have supplanted allozymes in recent years as the genetic markers of choice for many management and biological problems including genetic stock identification, parentage assignment, forensics, and genome mapping (Schlötterer and Pemberton 1994; Jarne and Lagoda 1996, Goldstein and Schlötterer 1999).

Copyright Text: Great Smoky Mountains National Park, Resource Management & Science, Fisheries Management Division

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