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Gene flow between sympatric life history forms of Oncorhynchus mykiss located above and below migratory barriers.

Van Doornik DM, Berejikian BA, Campbell LA - PLoS ONE (2013)

Bottom Line: We found that the population structure of the O. mykiss in these rivers appears to be influenced more by the presence of a barrier to upstream migration than by life history type.Most (89%) of the resident O. mykiss that produced anadromous offspring were males.Our results add to the growing body of evidence that shows that gene flow does readily occur between sympatric resident and anadromous O. mykiss life history types, and indicates that resident O. mykiss populations may be a potential repository of genes for the anadromous life history type.

View Article: PubMed Central - PubMed

Affiliation: Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Manchester, Washington, United States of America.

ABSTRACT
Oncorhynchus mykiss have a diverse array of life history types, and understanding the relationship among types is important for management of the species. Patterns of gene flow between sympatric freshwater resident O. mykiss, commonly known as rainbow trout, and anadromous O. mykiss, commonly known as steelhead, populations are complex and poorly understood. In this study, we attempt to determine the occurrence and pathways of gene flow and the degree of genetic similarity between sympatric resident and anadromous O. mykiss in three river systems, and investigate whether resident O. mykiss are producing anadromous offspring in these rivers, two of which have complete barriers to upstream migration. We found that the population structure of the O. mykiss in these rivers appears to be influenced more by the presence of a barrier to upstream migration than by life history type. The sex ratio of resident O. mykiss located above a barrier, and smolts captured in screw traps was significantly skewed in favor of females, whereas the reverse was true below the barriers, suggesting that male resident O. mykiss readily migrate downstream over the barrier, and that precocious male maturation may be occurring in the anadromous populations. Through paternity analyses, we also provide direct confirmation that resident O. mykiss can produce offspring that become anadromous. Most (89%) of the resident O. mykiss that produced anadromous offspring were males. Our results add to the growing body of evidence that shows that gene flow does readily occur between sympatric resident and anadromous O. mykiss life history types, and indicates that resident O. mykiss populations may be a potential repository of genes for the anadromous life history type.

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Related in: MedlinePlus

Pictorial representation of the hypothetical population structures tested for resident and anadromous O. mykiss samples.The small and large fish icons represent resident and anadromous O. mykiss, respectively, the falls represent a barrier to upstream migration, and the green ovals encompass the life-history type and location of fish considered as a single population for each scenario. For the Skokomish River, which does not contain a barrier to migration, only the one population, panmixia (A), and two population, resident / anadromous (C) scenarios were considered.
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pone-0079931-g002: Pictorial representation of the hypothetical population structures tested for resident and anadromous O. mykiss samples.The small and large fish icons represent resident and anadromous O. mykiss, respectively, the falls represent a barrier to upstream migration, and the green ovals encompass the life-history type and location of fish considered as a single population for each scenario. For the Skokomish River, which does not contain a barrier to migration, only the one population, panmixia (A), and two population, resident / anadromous (C) scenarios were considered.

Mentions: Several possible configurations of population structure within each river were tested to determine which one more closely defines the true configuration. Our samples could be sub-divided based upon life history type (resident O. mykiss vs. anadromous O. mykiss) as defined above, and for the Duckabush and Hamma Hamma rivers, based upon location above or below a barrier to upstream migration. We hypothesized that one of four different configurations of population sub-division could be present, and divided samples within each river into groups accordingly for analyses (Figure 2). We used three methods to search for the population structure configuration that showed the most differentiation among sample groups, thus representing the greatest departure from panmixia. These results allowed us to make inferences about the number of distinct O. mykiss populations in each river.


Gene flow between sympatric life history forms of Oncorhynchus mykiss located above and below migratory barriers.

Van Doornik DM, Berejikian BA, Campbell LA - PLoS ONE (2013)

Pictorial representation of the hypothetical population structures tested for resident and anadromous O. mykiss samples.The small and large fish icons represent resident and anadromous O. mykiss, respectively, the falls represent a barrier to upstream migration, and the green ovals encompass the life-history type and location of fish considered as a single population for each scenario. For the Skokomish River, which does not contain a barrier to migration, only the one population, panmixia (A), and two population, resident / anadromous (C) scenarios were considered.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3818241&req=5

pone-0079931-g002: Pictorial representation of the hypothetical population structures tested for resident and anadromous O. mykiss samples.The small and large fish icons represent resident and anadromous O. mykiss, respectively, the falls represent a barrier to upstream migration, and the green ovals encompass the life-history type and location of fish considered as a single population for each scenario. For the Skokomish River, which does not contain a barrier to migration, only the one population, panmixia (A), and two population, resident / anadromous (C) scenarios were considered.
Mentions: Several possible configurations of population structure within each river were tested to determine which one more closely defines the true configuration. Our samples could be sub-divided based upon life history type (resident O. mykiss vs. anadromous O. mykiss) as defined above, and for the Duckabush and Hamma Hamma rivers, based upon location above or below a barrier to upstream migration. We hypothesized that one of four different configurations of population sub-division could be present, and divided samples within each river into groups accordingly for analyses (Figure 2). We used three methods to search for the population structure configuration that showed the most differentiation among sample groups, thus representing the greatest departure from panmixia. These results allowed us to make inferences about the number of distinct O. mykiss populations in each river.

Bottom Line: We found that the population structure of the O. mykiss in these rivers appears to be influenced more by the presence of a barrier to upstream migration than by life history type.Most (89%) of the resident O. mykiss that produced anadromous offspring were males.Our results add to the growing body of evidence that shows that gene flow does readily occur between sympatric resident and anadromous O. mykiss life history types, and indicates that resident O. mykiss populations may be a potential repository of genes for the anadromous life history type.

View Article: PubMed Central - PubMed

Affiliation: Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Manchester, Washington, United States of America.

ABSTRACT
Oncorhynchus mykiss have a diverse array of life history types, and understanding the relationship among types is important for management of the species. Patterns of gene flow between sympatric freshwater resident O. mykiss, commonly known as rainbow trout, and anadromous O. mykiss, commonly known as steelhead, populations are complex and poorly understood. In this study, we attempt to determine the occurrence and pathways of gene flow and the degree of genetic similarity between sympatric resident and anadromous O. mykiss in three river systems, and investigate whether resident O. mykiss are producing anadromous offspring in these rivers, two of which have complete barriers to upstream migration. We found that the population structure of the O. mykiss in these rivers appears to be influenced more by the presence of a barrier to upstream migration than by life history type. The sex ratio of resident O. mykiss located above a barrier, and smolts captured in screw traps was significantly skewed in favor of females, whereas the reverse was true below the barriers, suggesting that male resident O. mykiss readily migrate downstream over the barrier, and that precocious male maturation may be occurring in the anadromous populations. Through paternity analyses, we also provide direct confirmation that resident O. mykiss can produce offspring that become anadromous. Most (89%) of the resident O. mykiss that produced anadromous offspring were males. Our results add to the growing body of evidence that shows that gene flow does readily occur between sympatric resident and anadromous O. mykiss life history types, and indicates that resident O. mykiss populations may be a potential repository of genes for the anadromous life history type.

Show MeSH
Related in: MedlinePlus