Evidence for divergent selection between the molecular forms of Anopheles gambiae: role of predation

The molecular forms of Anopheles gambiae are undergoing speciation. They are characterized by a strong assortative mating and they display partial habitat segregation. The M form is mostly found in flooded/irrigated areas whereas the S form dominates in the surrounding areas, but the ecological factors that shape this habitat segregation are not known. Resource competition has been demonstrated between species undergoing divergent selection, but resource competition is not the only factor that can lead to divergence. In a field experiment using transplantation of first instar larvae, we evaluated the role of larval predators in mediating habitat segregation between the forms. We found a significant difference in the ability of the molecular forms to exploit the different larval sites conditioned on the presence of predators. In absence of predation, the molecular forms outcompeted each other in their respective natural habitats however, the developmental success of the M form was significantly higher than that of the S form in both habitats under predator pressure. Our results provide the first empirical evidence for specific adaptive differences between the molecular forms and stress the role of larval predation as one of the mechanisms contributing to their divergence.https://doi.org/10.1186/1471-2148-8-

Distribution of developmental time of the molecular forms in each habitat (by sex)

<p><b>Copyright information:</b></p><p>Taken from "Evidence for divergent selection between the molecular forms of : role of predation"</p><p>http://www.biomedcentral.com/1471-2148/8/5</p><p>BMC Evolutionary Biology 2008;8():5-5.</p><p>Published online 11 Jan 2008</p><p>PMCID:PMC2217532.</p><p></p> Developmental Time was measured from transplantation of first instar to adult. The box extends between the 25and the 75percentile (across the inter quartile range – IQR) and the median is denoted by a thick line. The whiskers extend up to the most extreme value, up to 1.5 times the IQR and values located over 2 IQR from the median are shown. The triangles extend from the mean (base) to 1 SD (tip)

Larval developmental success (measured as the number of adults per cage) of the molecular forms in presence and absence of predators in puddles and rice fields

<p><b>Copyright information:</b></p><p>Taken from "Evidence for divergent selection between the molecular forms of : role of predation"</p><p>http://www.biomedcentral.com/1471-2148/8/5</p><p>BMC Evolutionary Biology 2008;8():5-5.</p><p>Published online 11 Jan 2008</p><p>PMCID:PMC2217532.</p><p></p> The box extends between the 25and the 75percentile (across the inter quartile range – IQR) and the median is denoted by a thick line. The whiskers extend up to the most extreme value, up to 1.5 times the IQR and values located over 2 IQR from the median are shown. The triangles extend from the mean (base) to 1 SD (tip)

Predator composition in rice fields (empty squares) and puddles (filled squares)

<p><b>Copyright information:</b></p><p>Taken from "Evidence for divergent selection between the molecular forms of : role of predation"</p><p>http://www.biomedcentral.com/1471-2148/8/5</p><p>BMC Evolutionary Biology 2008;8():5-5.</p><p>Published online 11 Jan 2008</p><p>PMCID:PMC2217532.</p><p></p> Bars denote mean density in 10 samples of rice fields and 9 samples of puddles of each predator. Stars above bars denote significant difference in a single test. Inset shows clustering of samples based on their predator composition using Principal Component (PC) analysis. Coordinates are the first (horizontal) and second principal components. The first PC represented overall predator abundance because its eigenvector's loadings were positive and similar in magnitude (except for the negative loading of the dragonfly; not shown). It alone accounted for 38% of the total variation and together with the second PC, 64% of the total variation was captured