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

Abstract

BackgroundThe 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.ResultsIn 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.ConclusionOur 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.

Evidence for carry-over effects of predator exposure on pathogen transmission potential

“…This may provide us a possible explanation to the paddies paradox, which describes situations where land irrigation increases mosquito populations without any increase in malaria transmission [49]. In permanent water collections, the density of predators is generally higher than in temporary water [24] and it may, therefore, contribute to reducing malaria transmission. In a time of renewed scientific and political commitment to malaria control and against biodiversity erosion, the biological conservation of predators in natural mosquito larval habitats is an obvious need.…”

“…The backswimmer A. jaczewskii (Hemiptera: Notonectidae) is the most abundant and widespread predatory bug in mosquito larval habitats in our study area [24]. Predators were collected in Bama rice fields and were fed daily ad libitum with An.…”

“…gambiae s.s.), which is one of the main vectors of P. falciparum in Africa, and the backswimmer Anisops jaczewskii, which is the most important predator of An. coluzzii larvae in Burkina Faso [24]. Previous studies on this system showed that Anopheles larvae display significant anti-predator behaviours in the presence of backswimmers, consisting of both lower feeding rates and activity [25,26].…”

Climate Change and Highland Malaria: Fresh Air for a Hot Debate

“…(Munga et al 2006) • Indirect effects of predator presence in larval habitat selection by molecular forms of An. gambiae (Diabate et al 2008) • Predation perception and resource abundance can modify phenotypic and life cycle traits of non-malaria mosquitoes (Beketov and Liess 2007).…”

Adaptive divergence between incipient species of Anopheles gambiae increases resistance to Plasmodium

“…The S form breeds in small ephemeral pools and puddles across sub-Saharan Africa, whereas the M form exploits larger, more stable breeding sites closely associated with agricultural or urban activity in West and Central Africa. Moreover, recent field studies have suggested fitness tradeoffs apparently related to the stability of their respective breeding sites (12,13). The S form develops more rapidly and outcompetes M in predator-free space, but the M form is superior at predator avoidance, as expected in an ecotype adapted to longer-lived habitats.…”