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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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Collection sites and frequencies of Anopheles farauti s.s. and Anopheles irenicus mosquitoes used in this study. Dots indicate several nearer sampling sites. Pie charts represent the proportion of species collected from each site. Inset: The study area within Melanesia is shown.
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Figure 1: Collection sites and frequencies of Anopheles farauti s.s. and Anopheles irenicus mosquitoes used in this study. Dots indicate several nearer sampling sites. Pie charts represent the proportion of species collected from each site. Inset: The study area within Melanesia is shown.

Mentions: Adult mosquitoes were collected from Tamboko 2 and Tavavao on Guadalcanal (Fig. 1 and details in [additional files 1 and 2]), and all of them were An. farauti s.s. (n = 51). We never collected An. irenicus on human baits. A total of 84 larvae were collected from 24 water bodies from five sites on Guadalcanal: Tamboko 2, Komimbo, Sopapera, Koli and Patima; and from two sites on Malaita: Fiu and Mawa (Fig. 1 and details in [additional files 1 and 2]). An. irenicus (n = 43) were only found in fresh water on Guadalcanal. The other 41 larvae were An. farauti s.s. and were mostly (n = 29, 70.7%) obtained from brackish water on Guadalcanal and Malaita. Only 12 An. farauti s.s. shared five out of the 20 water bodies with An. irenicus on Guadalcanal, and all five sites were fresh water bodies.


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)

Collection sites and frequencies of Anopheles farauti s.s. and Anopheles irenicus mosquitoes used in this study. Dots indicate several nearer sampling sites. Pie charts represent the proportion of species collected from each site. Inset: The study area within Melanesia is shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: Collection sites and frequencies of Anopheles farauti s.s. and Anopheles irenicus mosquitoes used in this study. Dots indicate several nearer sampling sites. Pie charts represent the proportion of species collected from each site. Inset: The study area within Melanesia is shown.
Mentions: Adult mosquitoes were collected from Tamboko 2 and Tavavao on Guadalcanal (Fig. 1 and details in [additional files 1 and 2]), and all of them were An. farauti s.s. (n = 51). We never collected An. irenicus on human baits. A total of 84 larvae were collected from 24 water bodies from five sites on Guadalcanal: Tamboko 2, Komimbo, Sopapera, Koli and Patima; and from two sites on Malaita: Fiu and Mawa (Fig. 1 and details in [additional files 1 and 2]). An. irenicus (n = 43) were only found in fresh water on Guadalcanal. The other 41 larvae were An. farauti s.s. and were mostly (n = 29, 70.7%) obtained from brackish water on Guadalcanal and Malaita. Only 12 An. farauti s.s. shared five out of the 20 water bodies with An. irenicus on Guadalcanal, and all five sites were fresh water bodies.

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