Detailed Research Information

Detailed project information for
Study Plan Number 08048

Branch : Northern Appalachian Research Laboratory

Study Plan Number : 08048

Study Title : Understanding fragmentation: A comparison of population structure between rare and common species of freshwater mussels in the upper Delaware River

Starting Date : 11/01/2005

Completion Date : 09/30/2008

Principal Investigator(s) : Ward, Rocky

Primary PI : Ward, Rocky

Telephone Number : (570) 724-3322 ext.

Email Address : rward@usgs.gov

SIS Number :

Primary Program Element :

Second Program Element :

Status : Active

Abstract : BACKGROUND
Mussels of the family Unionidae are found on all continents except Antarctica, reaching their greatest diversity in eastern North American where 43 genera and about 300 species have been described (Lévêque et al., 2005). Many of these species have limited distributions and many are threatened or endangered. Management of these species is hampered by lack of information on life history, ecology, and genetic population structure. Even when the population structure of a unionid species has been explored using genetic markers, the data are often difficult to interpret due to lack of information on genetic variation in non-impacted mussel populations. For example, five populations of the federally endangered dwarf wedgemussel, Alasmidonta heterodon, occurring over a 100 km stretch of the Delaware River were examined using nuclear DNA fragments containing microsatellites (Shaw, 2004). A statistically significant correlation between genetic distance and geographic distance was observed suggesting isolation by distance. Even populations as close as 12 km were genetically differentiated, indicating very limited gene flow between the populations. Because there is no historical data on A. heterodon distribution or abundance in the Delaware River, questions remain concerning whether the observed differentiation can be attributed to a bottleneck the population had undergone, an expansion of the population into new habitats, or normal patterns of spatial differentiation within stable riverine unionid populations. This project will compare genetic structure of highly fragmented A. heterodon populations with that of a more common mussel species with a ubiquitous distribution in the Delaware basin, Elliptio complanata.

Prior research has been performed comparing populations of E. complanata collected from tributaries of the St. Lawrence River basin in northern New York. Single-strand conformation polymorphism (SSCP) analysis of two mitochondrial genes revealed six cytochrome c oxidase subunit I alleles and four 16s rRNA alleles indicating that large-scale population structure exists between these collections (Temkin et al., 2000). In a similar study, E. complanata mitochondrial DNA sequence variation (cytochrome c oxidase subunit I and 16s rRNA) suggested that restricted gene flow and fragmentation events historically occurred that influenced the geographical distribution of E. complanata haplotypes in northern New York (Hayes et al., 2003).

In the present study, microsatellite markers will be developed for E. complanata. These nuclear diploid markers are used to examine fine-scale population structure that is undetectable with haploid mitochondrial DNA markers (Schlotterer and Pemberton, 1994). These markers will also be tested on Anodonta implicata representing an aggregated distribution in the Delaware basin and, if amplification is successful, data will be obtained from this species and compared to E. complanata and A. heterodon. If amplification is unsuccessful and adequate resources are available, we will develop new microsatellite markers specifically for A. implicata. These comparisons will provide resource managers insight into within basin population structure of unionids and assist in forming future management decisions regarding conservation of A. heterodon.
OBJECTIVES
1. Develop a suite of microsatellite markers for E. complanata

2. Determine utility of cross-species amplification of these new markers for other unionids - especially A. implicata

3. Develop microsatellite markers for A. implicata (if E. complanata markers do not work for A. implicata and if adequate resources are available)

4. Determine genetic relationships of E. complanata mussels found within the Delaware River basin

5. Determine genetic relationships of A. implicata mussels found within the Delaware River basin

6. Compare data from prior A. heterodon studies to data from the present study
HYPOTHESES TO BE TESTED
1. No genetic difference exists among populations of E. complanata in the Delaware River Basin

2. No genetic difference exists among populations of A. implicata in the Delaware River Basin

3. Levels of genetic variation observed with E. complanata in the Delaware basin are not significantly different from levels of variation observed with A. heterodon in the Delaware basin as reported in previous studies

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Branch :	Northern Appalachian Research Laboratory
Study Plan Number :	08048
Study Title :	Understanding fragmentation: A comparison of population structure between rare and common species of freshwater mussels in the upper Delaware River
Starting Date :	11/01/2005
Completion Date :	09/30/2008
Principal Investigator(s) :	Ward, Rocky
Primary PI :	Ward, Rocky
Telephone Number :	(570) 724-3322 ext.
Email Address :	rward@usgs.gov
SIS Number :
Primary Program Element :
Second Program Element :
Status :	Active
Abstract :	BACKGROUND Mussels of the family Unionidae are found on all continents except Antarctica, reaching their greatest diversity in eastern North American where 43 genera and about 300 species have been described (Lévêque et al., 2005). Many of these species have limited distributions and many are threatened or endangered. Management of these species is hampered by lack of information on life history, ecology, and genetic population structure. Even when the population structure of a unionid species has been explored using genetic markers, the data are often difficult to interpret due to lack of information on genetic variation in non-impacted mussel populations. For example, five populations of the federally endangered dwarf wedgemussel, Alasmidonta heterodon, occurring over a 100 km stretch of the Delaware River were examined using nuclear DNA fragments containing microsatellites (Shaw, 2004). A statistically significant correlation between genetic distance and geographic distance was observed suggesting isolation by distance. Even populations as close as 12 km were genetically differentiated, indicating very limited gene flow between the populations. Because there is no historical data on A. heterodon distribution or abundance in the Delaware River, questions remain concerning whether the observed differentiation can be attributed to a bottleneck the population had undergone, an expansion of the population into new habitats, or normal patterns of spatial differentiation within stable riverine unionid populations. This project will compare genetic structure of highly fragmented A. heterodon populations with that of a more common mussel species with a ubiquitous distribution in the Delaware basin, Elliptio complanata. Prior research has been performed comparing populations of E. complanata collected from tributaries of the St. Lawrence River basin in northern New York. Single-strand conformation polymorphism (SSCP) analysis of two mitochondrial genes revealed six cytochrome c oxidase subunit I alleles and four 16s rRNA alleles indicating that large-scale population structure exists between these collections (Temkin et al., 2000). In a similar study, E. complanata mitochondrial DNA sequence variation (cytochrome c oxidase subunit I and 16s rRNA) suggested that restricted gene flow and fragmentation events historically occurred that influenced the geographical distribution of E. complanata haplotypes in northern New York (Hayes et al., 2003). In the present study, microsatellite markers will be developed for E. complanata. These nuclear diploid markers are used to examine fine-scale population structure that is undetectable with haploid mitochondrial DNA markers (Schlotterer and Pemberton, 1994). These markers will also be tested on Anodonta implicata representing an aggregated distribution in the Delaware basin and, if amplification is successful, data will be obtained from this species and compared to E. complanata and A. heterodon. If amplification is unsuccessful and adequate resources are available, we will develop new microsatellite markers specifically for A. implicata. These comparisons will provide resource managers insight into within basin population structure of unionids and assist in forming future management decisions regarding conservation of A. heterodon. OBJECTIVES 1. Develop a suite of microsatellite markers for E. complanata 2. Determine utility of cross-species amplification of these new markers for other unionids - especially A. implicata 3. Develop microsatellite markers for A. implicata (if E. complanata markers do not work for A. implicata and if adequate resources are available) 4. Determine genetic relationships of E. complanata mussels found within the Delaware River basin 5. Determine genetic relationships of A. implicata mussels found within the Delaware River basin 6. Compare data from prior A. heterodon studies to data from the present study HYPOTHESES TO BE TESTED 1. No genetic difference exists among populations of E. complanata in the Delaware River Basin 2. No genetic difference exists among populations of A. implicata in the Delaware River Basin 3. Levels of genetic variation observed with E. complanata in the Delaware basin are not significantly different from levels of variation observed with A. heterodon in the Delaware basin as reported in previous studies
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U.S. Department of the Interior \|\| U.S. Geological Survey 11700 Leetown Road, Kearneysville, WV 25430, USA URL: http://www.lsc.usgs.gov Maintainer: lsc_webmaster@usgs.gov Last Modified: October 21, 2002 dwn Privacy Policy and Disclaimers \|\| FOIA \|\| Accessibility