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Spatial swarm segregation and reproductive isolation between the molecular forms of Anopheles gambiae.

Diabaté A, Dao A, Yaro AS, Adamou A, Gonzalez R, Manoukis NC, Traoré SF, Gwadz RW, Lehmann T - Proc. Biol. Sci. (2009)

Bottom Line: We found evidence of clustering of swarms composed of individuals of a single molecular form within the village.We argue that our results provide evidence that swarm spatial segregation strongly contributes to reproductive isolation between the molecular forms in Mali.However this does not exclude the possibility of additional mate recognition operating across the range distribution of the forms.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA.

ABSTRACT
Anopheles gambiae, the major malaria vector in Africa, can be divided into two subgroups based on genetic and ecological criteria. These two subgroups, termed the M and S molecular forms, are believed to be incipient species. Although they display differences in the ecological niches they occupy in the field, they are often sympatric and readily hybridize in the laboratory to produce viable and fertile offspring. Evidence for assortative mating in the field was recently reported, but the underlying mechanisms awaited discovery. We studied swarming behaviour of the molecular forms and investigated the role of swarm segregation in mediating assortative mating. Molecular identification of 1145 males collected from 68 swarms in Donéguébougou, Mali, over 2 years revealed a strict pattern of spatial segregation, resulting in almost exclusively monotypic swarms with respect to molecular form. We found evidence of clustering of swarms composed of individuals of a single molecular form within the village. Tethered M and S females were introduced into natural swarms of the M form to verify the existence of possible mate recognition operating within-swarm. Both M and S females were inseminated regardless of their form under these conditions, suggesting no within-mate recognition. We argue that our results provide evidence that swarm spatial segregation strongly contributes to reproductive isolation between the molecular forms in Mali. However this does not exclude the possibility of additional mate recognition operating across the range distribution of the forms. We discuss the importance of spatial segregation in the context of possible geographic variation in mechanisms of reproductive isolation.

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Association between landmarks and swarm of the molecular forms. The M forms swarm above areas of contrast on the landscape, whereas the S form uses no such contrast (table incorporated in figure). The figure gives a brief description of the swarming sites on the x-axis.
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RSPB20091167F3: Association between landmarks and swarm of the molecular forms. The M forms swarm above areas of contrast on the landscape, whereas the S form uses no such contrast (table incorporated in figure). The figure gives a brief description of the swarming sites on the x-axis.

Mentions: To understand the role of ground markers in swarm site selection by the molecular forms, all swarm sites were characterized (figure 2). All swarms of the S form were collected over bare ground, whereas the M form was strongly associated with markers consisting of contrasting dark/light pattern, such as the intersection of vegetation (dark) and footpath (light), a water well (dark) surrounded by bare ground (light), and a physical object such as a donkey cart, a chicken house, or a wall on a lighter background (figure 3). Although one M form swarm was found over bare ground, the association between swarm markers and swarm molecular form was highly significant (χ2 = 56.92, d.f. = 3, p < 0.0001). The mixed S/M swarm (14) was found over bare ground whereas the mixed M/An. arabiensis swarm (33) occurred over an intersection of grassland and footpath.


Spatial swarm segregation and reproductive isolation between the molecular forms of Anopheles gambiae.

Diabaté A, Dao A, Yaro AS, Adamou A, Gonzalez R, Manoukis NC, Traoré SF, Gwadz RW, Lehmann T - Proc. Biol. Sci. (2009)

Association between landmarks and swarm of the molecular forms. The M forms swarm above areas of contrast on the landscape, whereas the S form uses no such contrast (table incorporated in figure). The figure gives a brief description of the swarming sites on the x-axis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2821344&req=5

RSPB20091167F3: Association between landmarks and swarm of the molecular forms. The M forms swarm above areas of contrast on the landscape, whereas the S form uses no such contrast (table incorporated in figure). The figure gives a brief description of the swarming sites on the x-axis.
Mentions: To understand the role of ground markers in swarm site selection by the molecular forms, all swarm sites were characterized (figure 2). All swarms of the S form were collected over bare ground, whereas the M form was strongly associated with markers consisting of contrasting dark/light pattern, such as the intersection of vegetation (dark) and footpath (light), a water well (dark) surrounded by bare ground (light), and a physical object such as a donkey cart, a chicken house, or a wall on a lighter background (figure 3). Although one M form swarm was found over bare ground, the association between swarm markers and swarm molecular form was highly significant (χ2 = 56.92, d.f. = 3, p < 0.0001). The mixed S/M swarm (14) was found over bare ground whereas the mixed M/An. arabiensis swarm (33) occurred over an intersection of grassland and footpath.

Bottom Line: We found evidence of clustering of swarms composed of individuals of a single molecular form within the village.We argue that our results provide evidence that swarm spatial segregation strongly contributes to reproductive isolation between the molecular forms in Mali.However this does not exclude the possibility of additional mate recognition operating across the range distribution of the forms.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA.

ABSTRACT
Anopheles gambiae, the major malaria vector in Africa, can be divided into two subgroups based on genetic and ecological criteria. These two subgroups, termed the M and S molecular forms, are believed to be incipient species. Although they display differences in the ecological niches they occupy in the field, they are often sympatric and readily hybridize in the laboratory to produce viable and fertile offspring. Evidence for assortative mating in the field was recently reported, but the underlying mechanisms awaited discovery. We studied swarming behaviour of the molecular forms and investigated the role of swarm segregation in mediating assortative mating. Molecular identification of 1145 males collected from 68 swarms in Donéguébougou, Mali, over 2 years revealed a strict pattern of spatial segregation, resulting in almost exclusively monotypic swarms with respect to molecular form. We found evidence of clustering of swarms composed of individuals of a single molecular form within the village. Tethered M and S females were introduced into natural swarms of the M form to verify the existence of possible mate recognition operating within-swarm. Both M and S females were inseminated regardless of their form under these conditions, suggesting no within-mate recognition. We argue that our results provide evidence that swarm spatial segregation strongly contributes to reproductive isolation between the molecular forms in Mali. However this does not exclude the possibility of additional mate recognition operating across the range distribution of the forms. We discuss the importance of spatial segregation in the context of possible geographic variation in mechanisms of reproductive isolation.

Show MeSH
Related in: MedlinePlus