This poster, presenting
selected preliminary findings of an ongoing Cichla population genetics
study,
was presented at
the Brazilian Ichthyology Society meeting, January, 2005
Different Population Genetics Patterns in two
Species of Peacock Bass
(Cichla:Perciformes) of Tributaries of the
Rio Negro
Diferentes padrões genético-populacionais em duas espécies
de tucunarés
(Cichla:Perciformes) de tributários do rio Negro.
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Vasconcelos, W. R. (1); Nunes, M. S (1); Reiss,
P. (2); Farias, I. P. (1).
(1)Laboratory of Evolution and Animal Genetics - L.E.G.AL - UFAM.
(2) Acute Angling
rangel@inpa.gov.br
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The rivers Unini and Xeriuini are tributaries of the Rio Negro, itself
the largest tributary of the Amazon River. They harbor a great diversity
of aquatic vertebrates. To determine if the Rio Negro functions as
a barrier to the genetic flow between populations of non-migratory
fish, four populations of peacock bass of the species Cichla temensis
and Cichla orinocensis were sampled along the above cited affluents.
We used AMOVA and F statistics to test the hypothesis of population fragmentation,
with the objective of identifying the patterns of distribution of intra-specific
genetic variation. This information can furnish data about the evolutionary
dynamics of these two economically important species, not previously studied
in depth at the population level. |
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Tissue Samples were collected in the locations indicated on the map
(Fig. 1) and were preserved in 95% ethanol. The DNA was extracted
following the protocol for extraction by phenol-chloroform of Sambrook
et al. (1989). The region of the gene for ATPase was amplified via
PCR, with the use of primers specifically developed by Sivasundar et al.,
(2001). The sequencing reactions were performed in accordance with
the recommendations of the manufacturers utilizing the Terminator Cycle
Sequencing Kit (Amersham Bioscience), and analized in the MegaBACE 1000
automatic sequencer. |
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Intra and Inter-populational Analyses
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The genetic structure of the populations was analyzed using AMOVA (Analysis
of Molecular Variance) (Excoffier et al., 1992), and pairwise FsT (Cockerham
& Weir, 1993), implemented by the program Harlequin 2.0 (Schneider
et al., 2000). Indices of genetic diversity and tests of selective
neutrality of mutations were accessed using the program Harlequin 2.0.
The haplotype network was constructed with the program TCS versão
1.18 (Clement et al., 2000). |
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Fig. 2a- Example of C. orinocensis of the
Rio Unini
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Fig. 2b- Example of C. temensis of the
Rio Unini
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Based on the analyses of 605 base pairs and 46 gene copies, we found
11 haplotypes in C. temensis, with 1 most frequent and 9 singularly
occuring. While in the two populations of C. orinocensis,
we analyzed 25 gene copies, we found 10 haplotypes, 3 being more frequent
in relation to the rest. Values of genetic diversity in general were
more elevated in the populations of C. orinocensis than in
C.
temensis (Tab. 1). The neutral presumption of mutations was tested
through the index of selective neutrality Fs of Fu and indicated
genetic disequilibrium in the population of C. orinocensis and C.
temensis of the rio Unini (Tab. 1). Meanwhile D of Tajima indicated
a probable population growth only in C. temensis. Significant
values (P<0,05) of the parameter Fst were observed between the populations
of C. orinocensis, even with the correction of Bonferroni (Rice
1989).
 |
 |
Fig. 3a -Haplotype network showing the geneological
relationships between the ten haplotypes detected and identified in C.
orinocensis.
The color black indicates haplotypes found on the
Rio Unini and yellow indicates those of the Rio Xeriuini. |
Fig. 3b -Haplotype network showing the geneological
relationships between the ten haplotypes detected and identified in C.
temensis.
The color black indicates haplotypes found on the
Rio Unini and yellow indicates those of the Rio Xeriuini. |
Tab. 1- Principal measures of intra-specific genetic polymorphism
and tests of selective neutrality. P< 0.05.
Note: RU=Rio Unini and RX=Rio Xeriuini
|
Population
|
No. of
samples
|
No. of Poly-
morphic sites
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Genetic Diversity
|
Nucleotide Diversity
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D of Tajima
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Fsof Fu
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| RU-C. orinocensis |
11
|
10
|
0.9333 +/- 0.0773
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0.005657 +/- 0.003569
|
-0.14123
|
-3.11607 *
|
| RX-C. orinocensis |
14
|
10
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0.8901 +/- 0.0603
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0.005657 +/- 0.003569
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-0.68577
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-2.09245
|
| RU-C. temensis |
32
|
4
|
0.3377 +/- 0.1278
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0.000601 +/- 0.000672
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-1.87763 *
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-3.81699 *
|
| RX-C. temensis |
14
|
3
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0.2949 +/- 0.1558
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0.000763 +/- 0.000802
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-1.65231 *
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-0.68877
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Table 2a -Values of Pairwise Fst below the line and Effective
number of migrants (Nm) above the line for C. orinocensis.
Nota: RU=Rio Unini and RX=Rio Xeriuini.
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Poipulation
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RU-C. orinocensis
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RX-C. orinocensis
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| RU- C. orinocensis |
|
0.84186
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| RX-C. orinocensis |
0.23878 *
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Table 2b -Values of Pairwise Fst below the line and Effective
number of migrants (Nm) above the line for C. orinocensis. C.
temensis.
Nota: RU=Rio Unini and RX=Rio Xeriuini.
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Population
|
RU- C. temensis
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RX- C. temensis
|
| RU- C. temensis |
|
|
| RX- C. temensis |
0
|
|
|
| No indication of genetic difference was demonstrated in the
two populations of C. temensis, an indication of elevated genetic
flux. () (Tab. 3b).
The results of AMOVA also show this pattern. In the populations of
C.
orinocensis, 37,26% of the genetic variation occurred between the two
populations (Fst=0,372; P=0). While in C. temensis, the variation
between the two populations was -0,97% (Fst=-0,0096; P=0.7575). Fst
and AMOVA indicate population fragmentation in C. orinocensis.
These results demonstrate that a distance of ~100 Km between tributaries
of the Rio Negro can function as a barrier to the dispersion of some species
of fish as seen in C. orinocensis, but not in others as in C.
temensis. Species of peacock bass , for example, can exhibit different
patterns of migration, reflectining different life strategies. |
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Bibliography and References
|
Clement, M.; Posada, D. and Crandall, K. A. (2000)
TCS: a computer program to estimate gene 6 genealogies. Mol. Ecol., 9,
1657-1659.
Cockerham, C. C. and Weir B. S. (1993) Estimation
of gene flow from F-statistics. Evolution, 47, 855-863.
Excoffier, L.; Smouse, P. E. and Quattro, J. M. (1992)
Analysis of molecular variance inferred from metric distances among DNA
haplotypes: Application to human mitochondrial DNA restriction data. Genetics,
131, 479-491.
Rice. 1989. Analysing table of statistical tests.
Evolution 43: 223-225
Sambrook, J.; Fritsch, E. F. and Maniatis, T. (1989)
Molecular cloning: a laboratory manual, second edition Vol. 2. Cold Springs
Harbor Laboratory Press, Cold Springs Harbor, NY.
Schneider, S.; Roessli, D. and Excoffier, L. (2000).
Arlequin ver. 2000: A software for population genetic data analysis. Genetics
and Biometry Laboratory, University of Geneva. Geneva, Switzerland.
Sivasundar, A.; Bermigham, E. and Orti, G. 2001.
Population structure and biogeography of migratory freshwater fishes (Prochilodus:
Characiformes) in major South American rivers. Mol. Ecol. 10 (2): 407-417.
Xia, X. and Xie. Z. 2001 DAMBE: Data analysis in molecular
biology and evolution. Journal of Heredity 92:371-373. |
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Peacock Bass DNA Study Results - Portuguese
The 5 species of Peacock Bass
Gamefish of the Amazon Basin
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