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Hybrid sterility in crosses between two Brazilian sibling species of the Anopheles albitarsis complex.

Fontoura NG, Araki AS, Van Der Maas Azevedo R, Galardo AK, Peixoto AA, Lima JB - Parasit Vectors (2014)

Bottom Line: Results were compared to intraspecific crosses.This result is consistent with the Haldane's rule which states that in interspecific crosses the heterogametic sex is the first to be affected.However, the fact that the females are not completely sterile raises the possibility of introgression between these two siblings species.

View Article: PubMed Central - PubMed

Affiliation: Laboratório de Fisiologia e Controle de Artrópodes Vetores, Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, Brasil. giglio@ioc.fiocruz.br.

ABSTRACT

Background: Complexes of cryptic species are common in several taxa and this is also the case in the Anopheles genus, a group including all known human malaria vectors. The Anopheles albitarsis complex comprises at least nine cryptic species, some of which are implicated as vectors of human malaria. Several different types of data have been generated for this species complex such as cytogenetics, alloenzymes, morphological and feeding behavioral, hybridization experiments, RAPD-PCR and RFLP and mitochondrial and nuclear markers. Studies focused on its postzygotic isolation are still somewhat rare in the literature despite their importance to understand the speciation process and the level of gene flow potentially occurring among the different sibling species.

Methods: Hybridization experiments between Anopheles albitarsis s.s. and Anopheles marajoara, as well as backcrosses between hybrids and Anopheles albitarsis s.s., were performed using the induced mating technique. Results were compared to intraspecific crosses. Larva-to-adult viability and sex ratio were also assessed.

Results: Male hybrids show very low insemination rates and nearly complete sterility, apparently due to abnormalities in their reproductive organs. Evidence of partial sterility among the hybrid females was also observed.

Conclusions: Our data indicated that Anopheles albitarsis s.s. and Anopheles marajoara show a high level of postzygotic isolation with a strong hybrid male sterility. This result is consistent with the Haldane's rule which states that in interspecific crosses the heterogametic sex is the first to be affected. However, the fact that the females are not completely sterile raises the possibility of introgression between these two siblings species.

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Related in: MedlinePlus

Normalized insemination rates. (A)Crosses between females of different genotypes and Anopheles albitarsis s.s. males and (B) between males of different genotypes and Anopheles albitarsis s.s. females. **P < 0.01; ***P < 0.001.
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Fig2: Normalized insemination rates. (A)Crosses between females of different genotypes and Anopheles albitarsis s.s. males and (B) between males of different genotypes and Anopheles albitarsis s.s. females. **P < 0.01; ***P < 0.001.

Mentions: Figure 2 shows comparisonsbetween different crosses using the normalized insemination rates estimated fromTable 2 data. Normalization was carriedout using results from the intraspecific cross of An.albitarsis s.s.. Figure 2Aillustrates the normalized insemination rates involving females of differentgenotypes crossed to An. albitarsis s.s. males.In all cases, the difference between female insemination rates was notsignificant, regardless of their genotype. The results observed for the two typesof hybrid females were expected since they have a similar genotype.Figure 2B shows the normalizedinsemination data of An. albitarsis s.s.females mated to males of different genotypes. Comparing to the intraspecificcross, a significant reduction of insemination rates was observed in all othercrosses. Anopheles marajoara malesinefficiently inseminate An. albitarsis s.s.females (P < 0.01) and hybrid malesperformed even less successfully (P < 0.001). However, insemination rates of crosses using both typesof hybrid males did not differ significantly. Although some females inseminated byhybrid males laid eggs, their viability was (see Table 1).Figure 2


Hybrid sterility in crosses between two Brazilian sibling species of the Anopheles albitarsis complex.

Fontoura NG, Araki AS, Van Der Maas Azevedo R, Galardo AK, Peixoto AA, Lima JB - Parasit Vectors (2014)

Normalized insemination rates. (A)Crosses between females of different genotypes and Anopheles albitarsis s.s. males and (B) between males of different genotypes and Anopheles albitarsis s.s. females. **P < 0.01; ***P < 0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4264609&req=5

Fig2: Normalized insemination rates. (A)Crosses between females of different genotypes and Anopheles albitarsis s.s. males and (B) between males of different genotypes and Anopheles albitarsis s.s. females. **P < 0.01; ***P < 0.001.
Mentions: Figure 2 shows comparisonsbetween different crosses using the normalized insemination rates estimated fromTable 2 data. Normalization was carriedout using results from the intraspecific cross of An.albitarsis s.s.. Figure 2Aillustrates the normalized insemination rates involving females of differentgenotypes crossed to An. albitarsis s.s. males.In all cases, the difference between female insemination rates was notsignificant, regardless of their genotype. The results observed for the two typesof hybrid females were expected since they have a similar genotype.Figure 2B shows the normalizedinsemination data of An. albitarsis s.s.females mated to males of different genotypes. Comparing to the intraspecificcross, a significant reduction of insemination rates was observed in all othercrosses. Anopheles marajoara malesinefficiently inseminate An. albitarsis s.s.females (P < 0.01) and hybrid malesperformed even less successfully (P < 0.001). However, insemination rates of crosses using both typesof hybrid males did not differ significantly. Although some females inseminated byhybrid males laid eggs, their viability was (see Table 1).Figure 2

Bottom Line: Results were compared to intraspecific crosses.This result is consistent with the Haldane's rule which states that in interspecific crosses the heterogametic sex is the first to be affected.However, the fact that the females are not completely sterile raises the possibility of introgression between these two siblings species.

View Article: PubMed Central - PubMed

Affiliation: Laboratório de Fisiologia e Controle de Artrópodes Vetores, Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, Brasil. giglio@ioc.fiocruz.br.

ABSTRACT

Background: Complexes of cryptic species are common in several taxa and this is also the case in the Anopheles genus, a group including all known human malaria vectors. The Anopheles albitarsis complex comprises at least nine cryptic species, some of which are implicated as vectors of human malaria. Several different types of data have been generated for this species complex such as cytogenetics, alloenzymes, morphological and feeding behavioral, hybridization experiments, RAPD-PCR and RFLP and mitochondrial and nuclear markers. Studies focused on its postzygotic isolation are still somewhat rare in the literature despite their importance to understand the speciation process and the level of gene flow potentially occurring among the different sibling species.

Methods: Hybridization experiments between Anopheles albitarsis s.s. and Anopheles marajoara, as well as backcrosses between hybrids and Anopheles albitarsis s.s., were performed using the induced mating technique. Results were compared to intraspecific crosses. Larva-to-adult viability and sex ratio were also assessed.

Results: Male hybrids show very low insemination rates and nearly complete sterility, apparently due to abnormalities in their reproductive organs. Evidence of partial sterility among the hybrid females was also observed.

Conclusions: Our data indicated that Anopheles albitarsis s.s. and Anopheles marajoara show a high level of postzygotic isolation with a strong hybrid male sterility. This result is consistent with the Haldane's rule which states that in interspecific crosses the heterogametic sex is the first to be affected. However, the fact that the females are not completely sterile raises the possibility of introgression between these two siblings species.

Show MeSH
Related in: MedlinePlus