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Genetic diversity in two sibling species of the Anopheles punctulatus group of mosquitoes on Guadalcanal in the Solomon Islands.

Hasan AU, Suguri S, Fujimoto C, Itaki RL, Harada M, Kawabata M, Bugoro H, Albino B - BMC Evol. Biol. (2008)

Bottom Line: However, there is a significant population genetic structure between the species (Phi CT = 0.863, P < 0.01; Phi ST = 0.865, P < 0.01 and FST = 0.878, P < 0.01).These findings suggest that An. irenicus and An. farauti s.s. are monophyletic sister species living in sympatry, and their populations on Guadalcanal have recently expanded.Consequently, the findings further suggest that An. irenicus diverged from the ancestral An. farauti s.s. on Guadalcanal.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of International Medical Zoology, Faculty of Medicine, Kagawa University, Kita, Kagawa, 761-0793, Japan. ahasan@med.kagawa-u.ac.jp

ABSTRACT

Background: The mosquito Anopheles irenicus, a member of the Anopheles punctulatus group, is geographically restricted to Guadalcanal in the Solomon Islands. It shows remarkable morphological similarities to one of its sibling species, An. farauti sensu stricto (An. farauti s.s.), but is dissimilar in host and habitat preferences. To infer the genetic variations between these two species, we have analyzed mitochondrial cytochrome oxidase subunit II (COII) and nuclear ribosomal internal transcribed spacer 2 (ITS2) sequences from Guadalcanal and from one of its nearest neighbours, Malaita, in the Solomon Islands.

Results: An. farauti s.s. was collected mostly from brackish water and by the human bait method on both islands, whereas An. irenicus was only collected from fresh water bodies on Guadalcanal Island. An. irenicus is distributed evenly with An. farauti s.s. (Phi SC = 0.033, 0.38%) and its range overlaps in three of the seven sampling sites. However, there is a significant population genetic structure between the species (Phi CT = 0.863, P < 0.01; Phi ST = 0.865, P < 0.01 and FST = 0.878, P < 0.01). Phylogenetic analyses suggest that An. irenicus is a monophyletic species, not a hybrid, and is closely related to the An. farauti s.s. on Guadalcanal. The time estimator suggests that An. irenicus diverged from the ancestral An. farauti s.s. on Guadalcanal within 29,000 years before present (BP). An. farauti s.s. expanded much earlier on Malaita (texp = 24,600 BP) than the populations on Guadalcanal (texp = 16,800 BP for An. farauti s.s. and 14,000 BP for An. irenicus).

Conclusion: These findings suggest that An. irenicus and An. farauti s.s. are monophyletic sister species living in sympatry, and their populations on Guadalcanal have recently expanded. Consequently, the findings further suggest that An. irenicus diverged from the ancestral An. farauti s.s. on Guadalcanal.

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Maximum Parsimony (MP) consensus tree for 684 bp COII haplotypes in mitochondrial DNA using the GTR+I+G model. The trees were rooted with D. melanogaster and Bi. hollandi. Bootstrap values of > 90% are shown above the branch in italics and posterior probability values of > 0.75 are shown below the branch. S and I indicate haplotypes of An. farauti s.s. of the Solomon Islands and An. irenicus, respectively. Collection sites are represented after haplotypes where sampled from multiple sites. G, Guadalcanal; M, Malaita; SI, Solomon Islands; PNG, Papua New Guinea; Van, Vanuatu Islands. Sample codes and GenBank accession number for each specimen are given in [additional file 1].
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Figure 2: Maximum Parsimony (MP) consensus tree for 684 bp COII haplotypes in mitochondrial DNA using the GTR+I+G model. The trees were rooted with D. melanogaster and Bi. hollandi. Bootstrap values of > 90% are shown above the branch in italics and posterior probability values of > 0.75 are shown below the branch. S and I indicate haplotypes of An. farauti s.s. of the Solomon Islands and An. irenicus, respectively. Collection sites are represented after haplotypes where sampled from multiple sites. G, Guadalcanal; M, Malaita; SI, Solomon Islands; PNG, Papua New Guinea; Van, Vanuatu Islands. Sample codes and GenBank accession number for each specimen are given in [additional file 1].

Mentions: We aligned all 26 An. farauti s.s. and 13 An. irenicus haplotypes obtained in this study along with 37 sequences from 32 commonly-occurring members of the genus Anopheles in this geographical region and two outgroups (Bironella hollandi and Drosophila melanogaster) for mitochondrial COII. The final alignment thus consisted of 687 bp. The phylogenetic trees constructed by the MP and Bayesian methods using these sequences were very similar in topology. Therefore, only a consensus MP tree topology is shown in Figure 2. Here, An. farauti s.s. haplotypes were found to be geographically highly structured and composed of two separate subgroups. In one subgroup, the two haplotypes of Papua New Guinea were grouped with the single haplotype of Vanuatu; in the other, all An. farauti s.s. haplotypes of the Solomon Islands were clustered together. An. irenicus formed a monophyletic clade and grouped with the An. farauti s.s. subgroup of the Solomon Islands with strong support (posterior probability = 0.93).


Genetic diversity in two sibling species of the Anopheles punctulatus group of mosquitoes on Guadalcanal in the Solomon Islands.

Hasan AU, Suguri S, Fujimoto C, Itaki RL, Harada M, Kawabata M, Bugoro H, Albino B - BMC Evol. Biol. (2008)

Maximum Parsimony (MP) consensus tree for 684 bp COII haplotypes in mitochondrial DNA using the GTR+I+G model. The trees were rooted with D. melanogaster and Bi. hollandi. Bootstrap values of > 90% are shown above the branch in italics and posterior probability values of > 0.75 are shown below the branch. S and I indicate haplotypes of An. farauti s.s. of the Solomon Islands and An. irenicus, respectively. Collection sites are represented after haplotypes where sampled from multiple sites. G, Guadalcanal; M, Malaita; SI, Solomon Islands; PNG, Papua New Guinea; Van, Vanuatu Islands. Sample codes and GenBank accession number for each specimen are given in [additional file 1].
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2612007&req=5

Figure 2: Maximum Parsimony (MP) consensus tree for 684 bp COII haplotypes in mitochondrial DNA using the GTR+I+G model. The trees were rooted with D. melanogaster and Bi. hollandi. Bootstrap values of > 90% are shown above the branch in italics and posterior probability values of > 0.75 are shown below the branch. S and I indicate haplotypes of An. farauti s.s. of the Solomon Islands and An. irenicus, respectively. Collection sites are represented after haplotypes where sampled from multiple sites. G, Guadalcanal; M, Malaita; SI, Solomon Islands; PNG, Papua New Guinea; Van, Vanuatu Islands. Sample codes and GenBank accession number for each specimen are given in [additional file 1].
Mentions: We aligned all 26 An. farauti s.s. and 13 An. irenicus haplotypes obtained in this study along with 37 sequences from 32 commonly-occurring members of the genus Anopheles in this geographical region and two outgroups (Bironella hollandi and Drosophila melanogaster) for mitochondrial COII. The final alignment thus consisted of 687 bp. The phylogenetic trees constructed by the MP and Bayesian methods using these sequences were very similar in topology. Therefore, only a consensus MP tree topology is shown in Figure 2. Here, An. farauti s.s. haplotypes were found to be geographically highly structured and composed of two separate subgroups. In one subgroup, the two haplotypes of Papua New Guinea were grouped with the single haplotype of Vanuatu; in the other, all An. farauti s.s. haplotypes of the Solomon Islands were clustered together. An. irenicus formed a monophyletic clade and grouped with the An. farauti s.s. subgroup of the Solomon Islands with strong support (posterior probability = 0.93).

Bottom Line: However, there is a significant population genetic structure between the species (Phi CT = 0.863, P < 0.01; Phi ST = 0.865, P < 0.01 and FST = 0.878, P < 0.01).These findings suggest that An. irenicus and An. farauti s.s. are monophyletic sister species living in sympatry, and their populations on Guadalcanal have recently expanded.Consequently, the findings further suggest that An. irenicus diverged from the ancestral An. farauti s.s. on Guadalcanal.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of International Medical Zoology, Faculty of Medicine, Kagawa University, Kita, Kagawa, 761-0793, Japan. ahasan@med.kagawa-u.ac.jp

ABSTRACT

Background: The mosquito Anopheles irenicus, a member of the Anopheles punctulatus group, is geographically restricted to Guadalcanal in the Solomon Islands. It shows remarkable morphological similarities to one of its sibling species, An. farauti sensu stricto (An. farauti s.s.), but is dissimilar in host and habitat preferences. To infer the genetic variations between these two species, we have analyzed mitochondrial cytochrome oxidase subunit II (COII) and nuclear ribosomal internal transcribed spacer 2 (ITS2) sequences from Guadalcanal and from one of its nearest neighbours, Malaita, in the Solomon Islands.

Results: An. farauti s.s. was collected mostly from brackish water and by the human bait method on both islands, whereas An. irenicus was only collected from fresh water bodies on Guadalcanal Island. An. irenicus is distributed evenly with An. farauti s.s. (Phi SC = 0.033, 0.38%) and its range overlaps in three of the seven sampling sites. However, there is a significant population genetic structure between the species (Phi CT = 0.863, P < 0.01; Phi ST = 0.865, P < 0.01 and FST = 0.878, P < 0.01). Phylogenetic analyses suggest that An. irenicus is a monophyletic species, not a hybrid, and is closely related to the An. farauti s.s. on Guadalcanal. The time estimator suggests that An. irenicus diverged from the ancestral An. farauti s.s. on Guadalcanal within 29,000 years before present (BP). An. farauti s.s. expanded much earlier on Malaita (texp = 24,600 BP) than the populations on Guadalcanal (texp = 16,800 BP for An. farauti s.s. and 14,000 BP for An. irenicus).

Conclusion: These findings suggest that An. irenicus and An. farauti s.s. are monophyletic sister species living in sympatry, and their populations on Guadalcanal have recently expanded. Consequently, the findings further suggest that An. irenicus diverged from the ancestral An. farauti s.s. on Guadalcanal.

Show MeSH