Behavioural determinants of gene flow in malaria vector populations: Anopheles gambiae males select large females as mates

FM Okanda¹ , A Dao² , BN Njiru¹ , J Arija¹ , HA Akelo¹ , Y Touré² , A Odulaja¹ , JC Beier³ , JI Githure¹ , G Yan⁴ , LC Gouagna¹ , BGJ Knols¹^,6 and GF Killeen¹^,3^,5

¹International Centre of Insect Physiology and Ecology, PO Box 30772, Nairobi, Kenya

²Ecole Nationale de Medecine, Medical Research and Training Centre, University of Mali, Bamako, Mali

³Department of Tropical Medicine, School of Public Health and Tropical Medicine, Tulane University Health Sciences Centre, 1430 Tulane Avenue, New Orleans, Louisiana, 70112, USA

⁴Department of Biological Science, 219 Hochsletter Hall, State University of New York, Buffalo, New York 14260, USA

⁵Department of Public Health and Epidemiology, Swiss Tropical Institute, Socinstrasse 57, PO Box CH-4002, Basel, Switzerland

⁶Laboratory of Entomology, Wageningen University Research Centre, PO Box 8031, 6700 EH, Wageningen, The Netherlands

author email corresponding author email

Malaria Journal 2002, 1:10doi:10.1186/1475-2875-1-10


Published:	14 August 2002

Abstract

Background

Plasmodium-refractory mosquitoes are being rapidly developed for malaria control but will only succeed if they can successfully compete for mates when released into the wild. Pre-copulatory behavioural traits maintain genetic population structure in wild mosquito populations and mating barriers have foiled previous attempts to control malaria vectors through sterile male release.

Methods

Varying numbers of virgin male and female Anopheles gambiae Giles, from two strains of different innate sizes, were allowed to mate under standardized conditions in laboratory cages, following which, the insemination status, oviposition success and egg batch size of each female was assessed. The influence of male and female numbers, strain combination and female size were determined using logistic regression, correlation analysis and a simple mechanistic model of male competition for females.

Results

Male An. gambiae select females on the basis of size because of much greater fecundity among large females. Even under conditions where large numbers of males must compete for a smaller number of females, the largest females are more likely to become inseminated, to successfully oviposit and to produce large egg batches.

Conclusions

Sexual selection, on the basis of size, could either promote or limit the spread of malaria-refractory genes into wild populations and needs to be considered in the continued development and eventual release of transgenic vectors. Fundamental studies of behavioural ecology in malaria vectors such as An. gambiae can have important implications for malaria control and should be prioritised for more extensive investigation in the future.