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Population Structure in the Roundtail Chub (Gila robusta Complex) of the Gila River Basin as Determined by Microsatellites: Evolutionary and Conservation Implications.

Dowling TE, Anderson CD, Marsh PC, Rosenberg MS - PLoS ONE (2015)

Bottom Line: Our results supported previous molecular studies based on allozymes and DNA sequences, which found that most genetic variance was explained by differences among local populations.Samples from most localities were so divergent species-level diagnostic markers were not found.No species exhibited strong isolation by distance over the entire stream network, but the two species typically found in headwaters, G. nigra and G. intermedia, exhibited greater than expected genetic similarity between geographically proximate populations, and usually clustered with individuals from the same geographic location and/or sub-basin.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences, PO Box 874501, Arizona State University, Tempe, Arizona, United States of America.

ABSTRACT
Ten microsatellite loci were characterized for 34 locations from roundtail chub (Gila robusta complex) to better resolve patterns of genetic variation among local populations in the lower Colorado River basin. This group has had a complex taxonomic history and previous molecular analyses failed to identify species diagnostic molecular markers. Our results supported previous molecular studies based on allozymes and DNA sequences, which found that most genetic variance was explained by differences among local populations. Samples from most localities were so divergent species-level diagnostic markers were not found. Some geographic samples were discordant with current taxonomy due to admixture or misidentification; therefore, additional morphological studies are necessary. Differences in spatial genetic structure were consistent with differences in connectivity of stream habitats, with the typically mainstem species, G. robusta, exhibiting greater genetic connectedness within the Gila River drainage. No species exhibited strong isolation by distance over the entire stream network, but the two species typically found in headwaters, G. nigra and G. intermedia, exhibited greater than expected genetic similarity between geographically proximate populations, and usually clustered with individuals from the same geographic location and/or sub-basin. These results highlight the significance of microevolutionary processes and importance of maintaining local populations to maximize evolutionary potential for this complex. Augmentation stocking as a conservation management strategy should only occur under extreme circumstances, and potential source populations should be geographically proximate stocks of the same species, especially for the headwater forms.

No MeSH data available.


Assignment probability plots for all sample locations of the Gila robusta complex, Arizona-New Mexico, for selected values of K.“K” represents the number of informed priors for that specific group of replicates and “H΄” is the statistic that measures consistency across replicate runs.
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pone.0139832.g005: Assignment probability plots for all sample locations of the Gila robusta complex, Arizona-New Mexico, for selected values of K.“K” represents the number of informed priors for that specific group of replicates and “H΄” is the statistic that measures consistency across replicate runs.

Mentions: BAPS and STRUCTURE were used to estimate the number of groups encompassed by the 34 samples. BAPS determined that K = 28 with each identified group represented by single samples except for two, one containing samples EFE and UEG from G. intermedia and the other comprised of most G. robusta samples (ARA, BLK, LEG, WCL, and VDP) and NMFKS from G. nigra. STRUCTURE was used to characterize assignment probability for all K from 2–34. There was inconsistency across replicates for more divergent samples (e.g., BOL and TRT), as indicated by their consistent assignment to different groups for each value of K and reduced h’ values for these replicates (Fig 5). The method of Evanno et al. [45] indicated K = 20 (ΔK = 16.0), and ln likelihood values also reached a plateau at K = 20, supporting that conclusion [42].


Population Structure in the Roundtail Chub (Gila robusta Complex) of the Gila River Basin as Determined by Microsatellites: Evolutionary and Conservation Implications.

Dowling TE, Anderson CD, Marsh PC, Rosenberg MS - PLoS ONE (2015)

Assignment probability plots for all sample locations of the Gila robusta complex, Arizona-New Mexico, for selected values of K.“K” represents the number of informed priors for that specific group of replicates and “H΄” is the statistic that measures consistency across replicate runs.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4608781&req=5

pone.0139832.g005: Assignment probability plots for all sample locations of the Gila robusta complex, Arizona-New Mexico, for selected values of K.“K” represents the number of informed priors for that specific group of replicates and “H΄” is the statistic that measures consistency across replicate runs.
Mentions: BAPS and STRUCTURE were used to estimate the number of groups encompassed by the 34 samples. BAPS determined that K = 28 with each identified group represented by single samples except for two, one containing samples EFE and UEG from G. intermedia and the other comprised of most G. robusta samples (ARA, BLK, LEG, WCL, and VDP) and NMFKS from G. nigra. STRUCTURE was used to characterize assignment probability for all K from 2–34. There was inconsistency across replicates for more divergent samples (e.g., BOL and TRT), as indicated by their consistent assignment to different groups for each value of K and reduced h’ values for these replicates (Fig 5). The method of Evanno et al. [45] indicated K = 20 (ΔK = 16.0), and ln likelihood values also reached a plateau at K = 20, supporting that conclusion [42].

Bottom Line: Our results supported previous molecular studies based on allozymes and DNA sequences, which found that most genetic variance was explained by differences among local populations.Samples from most localities were so divergent species-level diagnostic markers were not found.No species exhibited strong isolation by distance over the entire stream network, but the two species typically found in headwaters, G. nigra and G. intermedia, exhibited greater than expected genetic similarity between geographically proximate populations, and usually clustered with individuals from the same geographic location and/or sub-basin.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences, PO Box 874501, Arizona State University, Tempe, Arizona, United States of America.

ABSTRACT
Ten microsatellite loci were characterized for 34 locations from roundtail chub (Gila robusta complex) to better resolve patterns of genetic variation among local populations in the lower Colorado River basin. This group has had a complex taxonomic history and previous molecular analyses failed to identify species diagnostic molecular markers. Our results supported previous molecular studies based on allozymes and DNA sequences, which found that most genetic variance was explained by differences among local populations. Samples from most localities were so divergent species-level diagnostic markers were not found. Some geographic samples were discordant with current taxonomy due to admixture or misidentification; therefore, additional morphological studies are necessary. Differences in spatial genetic structure were consistent with differences in connectivity of stream habitats, with the typically mainstem species, G. robusta, exhibiting greater genetic connectedness within the Gila River drainage. No species exhibited strong isolation by distance over the entire stream network, but the two species typically found in headwaters, G. nigra and G. intermedia, exhibited greater than expected genetic similarity between geographically proximate populations, and usually clustered with individuals from the same geographic location and/or sub-basin. These results highlight the significance of microevolutionary processes and importance of maintaining local populations to maximize evolutionary potential for this complex. Augmentation stocking as a conservation management strategy should only occur under extreme circumstances, and potential source populations should be geographically proximate stocks of the same species, especially for the headwater forms.

No MeSH data available.