Swarming behaviour in natural populations of Anopheles gambiae and An. coluzzii: Review of 4 years survey in rural areas of sympatry, Burkina Faso (West Africa)

Abstract

The swarming and mating systems of natural populations of An. gambiae M and S forms were investigated through longitudinal surveys conducted between July 2006 and October 2009 in Soumousso and Vallée du Kou (VK7), two rural areas of south-western Burkina Faso where these forms are sympatric. In both sites, the majority of swarms were recorded above visual markers localized within human habitats. In Soumousso, a wooded area of savannah, 108 pairs caught in copula from 205 swarms were sampled; in VK7, a rice growing area, 491 couples from 250 swarms were sampled. In neither site was any spatial segregation observed between the swarm sites used by the two forms of An. gambiae, which shared many of their visual markers. Furthermore, mixed swarms were collected annually in frequencies varying from one © 2014. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ 2 site to another, though no mixed inseminations were recorded, corroborating the low hybrid rate previously reported in the field. The occurrence of inter-specific mate-recognition mechanisms, which allow individuals to avoid hybridization, is discussed.

Stimulating Anopheles gambiae swarms in the laboratory: application for behavioural and fitness studies

“…Although several studies describing A. gambiae mating behaviour in the field have been published since then [3, 4, 7, 16, 30, 31], parallel research in the insectary has not been developed. The main goals of swarm studies in the field have been to explain mating choice and reproductive isolation within the A. gambiae complex.…”

“…Swarms in Diptera are associated with overhanging trees, shrubs and contrasting-value ground markers [2], and among mosquitoes, swarms have been observed to occur during morning and evening twilight [1]. Anopheles gambiae swarms have been studied in the field, mainly in West Africa [4]. Males of this species specifically swarm near contrasting-shade ground features at evening twilight [4, 5], an activity lasting for approximately 30 min.…”

“…Anopheles gambiae swarms have been studied in the field, mainly in West Africa [4]. Males of this species specifically swarm near contrasting-shade ground features at evening twilight [4, 5], an activity lasting for approximately 30 min. Swarms are composed almost entirely of males into which females briefly fly and leave the swarm in copula [6].…”

“…Copulation lasts less than 20 s [6]. Swarms can contain up to thousands of males though tens to several hundred is more common [4, 7]. Field observations have produced the largest part of knowledge on mating behaviour of this species because A. gambiae swarms are difficult to obtain both in the laboratory and in large field cages [8], and such field work requires a great deal of experienced labour and long time periods to collect substantial data.…”

“…Little information is available on the male–female-environment interactions during mating [3, 4, 7, 16] and little is known of the molecular mechanisms that regulate these processes [17, 18]. …”