The Right Timing Makes the Good Vector: Daily Rhythms and how they Promote Adaptation to a Changing World in Major Malaria Vectors – ANORHYTHM

Populations of the most important human malaria vectors in Africa offer instances of ongoing adaptations to new ecological niches set by human actions in the context of global change, with the dramatic consequence of emerging and re-emerging sustained malaria transmission in new spaces and times. Hence, patent adaptations to permanent irrigated schemes, urban settlements and wide insecticides use lead to the conspicuous extension of the repartition area of Anopheles species, and set the scene for the emergence or re-emergence of sustained malaria transmission. Physiological mechanisms allowing malaria mosquitoes to colonize new human-made ecological niches are under scrutiny, however, less attention is given to behavioral modifications triggered by -or in response to-relevant environmental cues characterizing the new ecological niches. In particular, in what ways environmental pressure impact the periodic behavior of the mosquitoes has been overlooked. Insects’ adaptation and success in the colonization of the most diverse environments is associated with the temporal organization of their daily lives. Mosquito physiology and behavior are under rhythmic control, organized in a time-of-day specific manner and the resulting periodicities at the individual level organize insects’ community temporally, just as niche diversification can do so spatially. As mosquitoes exploit the natural oscillations of light, darkness, temperature, and resource availability to entrain their biological rhythms, differences in oscillatory characteristics associated with different environments have the potential to affect the physiological basis and overt expression of many of their periodic behaviors. Accordingly, adaptation to modified stimuli may not only be a requirement for surviving in new habitats, but it may also provide, through its effects on periodic behaviors associated with reproductive success, a mechanism of restriction to gene flow—a fundamental condition for local adaptation and, ultimately, speciation and the diversification of vectorial system. Resolutely rooted in the « real world » concept and working with infectious mosquitoes, we will merge the fields of climatology, behavioral ecology, evolutionary physiology, functional molecular biology, epidemiology, mathematical modelling and social sciences to expose new targets for control and generate niche-specific integrative models, with the aim to better predict risks of disease in the face of environmental changes. Specifically, our project aims at (i) identifying if epidemiologically relevant periodic behaviors show altered rhythmicity in front line populations (ii) determining adaptive value of these changes through the measure of the associated fitness costs or benefits (iii) measuring the extent to which behaviors are further altered by Plasmodium infections (iv) determine the outputs of infection in mosquitoes displaying altered periodicity. This multidisciplinary and integrative approach will generate new cues to understand the functional diversity of An. gambiae s.l., the cornerstone of its adaptive and invasive dynamics. At the applied level, we will generate niche-specific outputs to optimize current predictive models which will include social science data on human behavior, with the aim to better predict risks of disease in the context of global changes. Our study will highlight the fundamental roles that circadian rhythms play in malaria vectors adaptation, and, through the molecular approach, will suggest new targets for alternative innovative strategies. Our findings and resulting protocols will be easily applied to the study of virtually all disease vectors in all ecological settings.