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Analysis of the genetic diversity of the nematode parasite Baylisascaris schroederi from wild giant pandas in different mountain ranges in China.

Zhou X, Xie Y, Zhang ZH, Wang CD, Sun Y, Gu XB, Wang SX, Peng XR, Yang GY - Parasit Vectors (2013)

Bottom Line: For the DNA dataset, insignificant Fst values and a significant, high level of gene flow were detected among the three mountain populations of B. schroederi, and high genetic variation within populations and a low genetic distance were observed.Neutrality tests and mismatch analysis indicated that B. schroederi experienced a population expansion in the past.Taken together, the dispersed haplotype map, extremely high gene flow among the three populations of B. schroederi, low genetic structure and rapid evolutionary rate suggest that the B. schroederi populations did not follow a pattern of isolation by distance, indicating the existence of physical connections before these populations became geographically separated.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Parasitology, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, China.

ABSTRACT

Background: Baylisascaris schroederi is one of the most common nematodes of the giant panda, and can cause severe baylisascarosis in both wild and captive giant pandas. Previous studies of the giant pandas indicated that this population is genetically distinct, implying the presence of a new subspecies. Based on the co-evolution between the parasite and the host, the aim of this study was to investigate the genetic differentiation in the B. schroederi population collected from giant pandas inhabiting different mountain ranges, and further to identify whether the evolution of this parasite correlates with the evolution of giant pandas.

Methods: In this study, 48 B. schroederi were collected from 28 wild giant pandas inhabiting the Qinling, Minshan and Qionglai mountain ranges in China. The complete sequence of the mitochondrial cytochrome b (mtCytb) gene was amplified by PCR, and the corresponding population genetic diversity of the three mountain populations was determined. In addition, we discussed the evolutionary relationship between B. schroederi and its host giant panda.

Results: For the DNA dataset, insignificant Fst values and a significant, high level of gene flow were detected among the three mountain populations of B. schroederi, and high genetic variation within populations and a low genetic distance were observed. Both phylogenetic analyses and network mapping of the 16 haplotypes revealed a dispersed pattern and an absence of branches strictly corresponding to the three mountain range sampling sites. Neutrality tests and mismatch analysis indicated that B. schroederi experienced a population expansion in the past.

Conclusions: Taken together, the dispersed haplotype map, extremely high gene flow among the three populations of B. schroederi, low genetic structure and rapid evolutionary rate suggest that the B. schroederi populations did not follow a pattern of isolation by distance, indicating the existence of physical connections before these populations became geographically separated.

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MP and BI trees for the 16 mtCytb haplotypes. Maximum-parsimony, MP; Bayesian inference, BI. The numbers along branches indicate bootstrap values from different analyses in the order: MP/BI. B. transfuga as the outgroup.
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Figure 2: MP and BI trees for the 16 mtCytb haplotypes. Maximum-parsimony, MP; Bayesian inference, BI. The numbers along branches indicate bootstrap values from different analyses in the order: MP/BI. B. transfuga as the outgroup.

Mentions: To clarify the phylogenetic relationship among the haplotypes of the three populations of B. schroederi, the sequence divergence values to construct hypothetical phylogenetic trees were calculated by the MP method and BI procedure. The two methods of phylogenetic analysis using the mtCytb marker led to very similar trees with shallow branches (Figure 2). The topology of the resultant trees was supported by the bootstrap values. Interestingly, as shown in Figure 2, haplotype H7, which was specific to the Minshan population, closely clustered with haplotypes H9 and H11 in the Qionglai population; while the Minshan population-specific haplotype H3 was close to the Qinling population-specific haplotype H8; three haplotypes in the Qionglai population (H6, H12 and H15) clustered together; the other haplotypes formed isolated clusters. Several relationships among these haplotypes were also confirmed using the Network method (Figure 3). On the basis of the 16 haplotypes detected for the mtCytb gene, the network map revealed a star-like pattern around haplotype H1 (16 individuals, 33.3% of total haplotypes). Seven of the haplotypes were found in the Minshan population (H1-H7), three in the Qinling population (H1, H2, H8) and twelve in the Qionglai population (H1-H3, H6, H9-H16). While H1 and H2 were present in the populations from all three mountain ranges, haplotype H1, which had a cumulative frequency of 33.33%, was more frequent than H2 (18.8%). The Qionglai and Minshan populations shared haplotypes H3 and H6 (Figure 3). Furthermore, the haplotypes present in each mountain population were highly dispersed, and no obvious correlation of sampled clusters was detected.


Analysis of the genetic diversity of the nematode parasite Baylisascaris schroederi from wild giant pandas in different mountain ranges in China.

Zhou X, Xie Y, Zhang ZH, Wang CD, Sun Y, Gu XB, Wang SX, Peng XR, Yang GY - Parasit Vectors (2013)

MP and BI trees for the 16 mtCytb haplotypes. Maximum-parsimony, MP; Bayesian inference, BI. The numbers along branches indicate bootstrap values from different analyses in the order: MP/BI. B. transfuga as the outgroup.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750503&req=5

Figure 2: MP and BI trees for the 16 mtCytb haplotypes. Maximum-parsimony, MP; Bayesian inference, BI. The numbers along branches indicate bootstrap values from different analyses in the order: MP/BI. B. transfuga as the outgroup.
Mentions: To clarify the phylogenetic relationship among the haplotypes of the three populations of B. schroederi, the sequence divergence values to construct hypothetical phylogenetic trees were calculated by the MP method and BI procedure. The two methods of phylogenetic analysis using the mtCytb marker led to very similar trees with shallow branches (Figure 2). The topology of the resultant trees was supported by the bootstrap values. Interestingly, as shown in Figure 2, haplotype H7, which was specific to the Minshan population, closely clustered with haplotypes H9 and H11 in the Qionglai population; while the Minshan population-specific haplotype H3 was close to the Qinling population-specific haplotype H8; three haplotypes in the Qionglai population (H6, H12 and H15) clustered together; the other haplotypes formed isolated clusters. Several relationships among these haplotypes were also confirmed using the Network method (Figure 3). On the basis of the 16 haplotypes detected for the mtCytb gene, the network map revealed a star-like pattern around haplotype H1 (16 individuals, 33.3% of total haplotypes). Seven of the haplotypes were found in the Minshan population (H1-H7), three in the Qinling population (H1, H2, H8) and twelve in the Qionglai population (H1-H3, H6, H9-H16). While H1 and H2 were present in the populations from all three mountain ranges, haplotype H1, which had a cumulative frequency of 33.33%, was more frequent than H2 (18.8%). The Qionglai and Minshan populations shared haplotypes H3 and H6 (Figure 3). Furthermore, the haplotypes present in each mountain population were highly dispersed, and no obvious correlation of sampled clusters was detected.

Bottom Line: For the DNA dataset, insignificant Fst values and a significant, high level of gene flow were detected among the three mountain populations of B. schroederi, and high genetic variation within populations and a low genetic distance were observed.Neutrality tests and mismatch analysis indicated that B. schroederi experienced a population expansion in the past.Taken together, the dispersed haplotype map, extremely high gene flow among the three populations of B. schroederi, low genetic structure and rapid evolutionary rate suggest that the B. schroederi populations did not follow a pattern of isolation by distance, indicating the existence of physical connections before these populations became geographically separated.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Parasitology, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, China.

ABSTRACT

Background: Baylisascaris schroederi is one of the most common nematodes of the giant panda, and can cause severe baylisascarosis in both wild and captive giant pandas. Previous studies of the giant pandas indicated that this population is genetically distinct, implying the presence of a new subspecies. Based on the co-evolution between the parasite and the host, the aim of this study was to investigate the genetic differentiation in the B. schroederi population collected from giant pandas inhabiting different mountain ranges, and further to identify whether the evolution of this parasite correlates with the evolution of giant pandas.

Methods: In this study, 48 B. schroederi were collected from 28 wild giant pandas inhabiting the Qinling, Minshan and Qionglai mountain ranges in China. The complete sequence of the mitochondrial cytochrome b (mtCytb) gene was amplified by PCR, and the corresponding population genetic diversity of the three mountain populations was determined. In addition, we discussed the evolutionary relationship between B. schroederi and its host giant panda.

Results: For the DNA dataset, insignificant Fst values and a significant, high level of gene flow were detected among the three mountain populations of B. schroederi, and high genetic variation within populations and a low genetic distance were observed. Both phylogenetic analyses and network mapping of the 16 haplotypes revealed a dispersed pattern and an absence of branches strictly corresponding to the three mountain range sampling sites. Neutrality tests and mismatch analysis indicated that B. schroederi experienced a population expansion in the past.

Conclusions: Taken together, the dispersed haplotype map, extremely high gene flow among the three populations of B. schroederi, low genetic structure and rapid evolutionary rate suggest that the B. schroederi populations did not follow a pattern of isolation by distance, indicating the existence of physical connections before these populations became geographically separated.

Show MeSH
Related in: MedlinePlus