Genetic structure of Anopheles gambiae populations on islands in northwestern Lake Victoria, Uganda.
BACKGROUND
Alternative means of malaria control are urgently needed. Evaluating the effectiveness of measures that involve genetic manipulation of vector populations will be facilitated by identifying small, genetically isolated vector populations. The study was designed to use variation in microsatellite markers to look at genetic structure across four Lake Victoria islands and two surrounding mainland populations and for evidence of any restriction to free gene flow.


METHODS
Four Islands (from 20-50 km apart) and two surrounding mainland populations (96 km apart) were studied. Samples of indoor resting adult mosquitoes, collected over two consecutive years, were genotyped at microsatellite loci distributed broadly throughout the genome and analysed for genetic structure, effective migration (Nem) and effective population size (Ne).


RESULTS
Ne estimates showed island populations to consist of smaller demes compared to the mainland ones. Most populations were significantly differentiated geographically, and from one year to the other. Average geographic pair-wise FST ranged from 0.014-0.105 and several pairs of populations had Ne m < 3. The loci showed broad heterogeneity at capturing or estimating population differences.


CONCLUSIONS
These island populations are significantly genetically differentiated. Differences reoccurred over the study period, between the two mainland populations and between each other. This appears to be the product of their separation by water, dynamics of small populations and local adaptation. With further characterisation these islands could become possible sites for applying measures evaluating effectiveness of control by genetic manipulation.
Kayondo
Jonathan K
JK
Center for Tropical Disease Research and Training, University of Notre Dame, Notre Dame IN 46556-0369, USA. jkayondo@nd.edu
Mukwaya
Louis G
LG
Stump
Aram
A
Michel
Andrew P
AP
Coulibaly
Mamadou B
MB
Besansky
Nora J
NJ
Collins
Frank H
FH
D000818:Animals; D000852:Anopheles / Q000145:classification / Q000235:genetics*; D007446:Chromosome Inversion; D051456:Gene Flow / Q000235:genetics; D014644:Genetic Variation; D005838:Genotype; D005843:Geography; D007303:Insect Vectors / Q000145:classification / Q000235:genetics*; D016014:Linear Models; D018895:Microsatellite Repeats / Q000235:genetics; D016133:Polymerase Chain Reaction / Q000379:methods; D011110:Polymorphism, Genetic; D011156:Population Density; D013997:Time Factors; D014454:Uganda