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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.


Neighbor-joining network for sample locations of the Gila robusta complex constructed using pairwise estimates of FST.Location acronyms are provided in Table 1. Red, blue, and black labels and symbols identify samples from G. intermedia, G. nigra, and G. robusta, respectively. Numbers on branches reflect the proportion of 1000 bootstrap replicates in which the defined node was found.
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pone.0139832.g004: Neighbor-joining network for sample locations of the Gila robusta complex constructed using pairwise estimates of FST.Location acronyms are provided in Table 1. Red, blue, and black labels and symbols identify samples from G. intermedia, G. nigra, and G. robusta, respectively. Numbers on branches reflect the proportion of 1000 bootstrap replicates in which the defined node was found.

Mentions: Analysis of population structure independently for each species provides a different picture. Estimates of FST for G. robusta, G. nigra, and G. intermedia were comparable, and not significantly different among species (FST = 0.191, 0.338, and 0.287, respectively; P = 0.263). However, when samples from the Bill Williams River drainage (BOL, TRT) were excluded, the average for G. robusta dropped dramatically (FST = 0.071) and there were significant differences among the three species (P = 0.009). This is reflected in the neighbor joining network of pairwise FST values (Fig 4), where many samples of G. nigra and G. intermedia exhibited long terminal branches while samples of G. robusta (except for those from the Bill Williams drainage) were shorter. Most nodes were not supported by bootstrap analysis with the exception of some pairs of samples in relatively close proximity.


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)

Neighbor-joining network for sample locations of the Gila robusta complex constructed using pairwise estimates of FST.Location acronyms are provided in Table 1. Red, blue, and black labels and symbols identify samples from G. intermedia, G. nigra, and G. robusta, respectively. Numbers on branches reflect the proportion of 1000 bootstrap replicates in which the defined node was found.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0139832.g004: Neighbor-joining network for sample locations of the Gila robusta complex constructed using pairwise estimates of FST.Location acronyms are provided in Table 1. Red, blue, and black labels and symbols identify samples from G. intermedia, G. nigra, and G. robusta, respectively. Numbers on branches reflect the proportion of 1000 bootstrap replicates in which the defined node was found.
Mentions: Analysis of population structure independently for each species provides a different picture. Estimates of FST for G. robusta, G. nigra, and G. intermedia were comparable, and not significantly different among species (FST = 0.191, 0.338, and 0.287, respectively; P = 0.263). However, when samples from the Bill Williams River drainage (BOL, TRT) were excluded, the average for G. robusta dropped dramatically (FST = 0.071) and there were significant differences among the three species (P = 0.009). This is reflected in the neighbor joining network of pairwise FST values (Fig 4), where many samples of G. nigra and G. intermedia exhibited long terminal branches while samples of G. robusta (except for those from the Bill Williams drainage) were shorter. Most nodes were not supported by bootstrap analysis with the exception of some pairs of samples in relatively close proximity.

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.