Effects of co-habitation between Anopheles gambiae s.s. and Culex quinquefasciatus aquatic stages on life history traits

<p>Abstract</p> <p>Background</p> <p>The effective measures for the control of malaria and filariasis vectors can be achieved by targeting immature stages of anopheline and culicine mosquitoes in productive habitat. To design this strategy, the mechanisms (like biotic interactions with conspecifc and heterospecific larvae) regulating mosquito aquatic stages survivorship, development time and the size of emerging adults should be understood. This study explored the effect of co-habitation between <it>An. gambiae </it>s.s. and <it>Cx. quinquefasciatus </it>on different life history traits of both species under different densities and constant food supply in the habitats of the same size under semi-natural conditions.</p> <p>Methods</p> <p>Experiments were set up with three combinations; <it>Cx. quinquefasciatus </it>alone (single species treatment), <it>An. gambiae </it>s.s. alone (single species treatment); and <it>An. gambiae </it>s.s. with <it>Cx. quiquefasciatus </it>(co-habitation treatment) in different densities in semi field situation.</p> <p>Results</p> <p>The effect of co-habitation of <it>An. gambiae </it>s.s. and <it>Cx. quinquefasciatus </it>was found to principally affect three parameters. The wing-lengths (a proxy measure of body size) of <it>An. gambiae </it>s.s. in co-habitation treatments were significantly shorter in both females and males than in <it>An. gambiae </it>s.s single species treatments. In <it>Cx. quinquefasciatus</it>, no significant differences in wing-length were observed between the single species and co-habitation treatments. Daily survival rates were not significantly different between co-habitation and single species treatments for both <it>An. gambiae </it>s.s. and <it>Cx. quinquefasciatus</it>. Developmental time was found to be significantly different with single species treatments developing better than co-habitation treatments. Sex ratio was found to be significantly different from the proportion of 0.5 among single and co-habitation treatments species at different densities. Single species treatments had more males than females emerging while in co-habitation treatments more females emerged than males. In this study, there was no significant competitive survival advantage in co-habitation.</p> <p>Conclusion</p> <p>These results suggest that co-habitation of <it>An. gambiae </it>s.s. and <it>Cx. quinquefasciatus </it>in semi-natural conditions affect mostly <it>An. gambiae </it>s.s. body size. Hence, more has to be understood on the effects of co-habitation of <it>An. gambiae </it>s.s. and <it>Cx. quinquefasciatus </it>in a natural ecology and its possible consequences in malaria and filariasis epidemiology.</p

Agroforesterie et services écosystémiques en zone tropicale

Respectueux de l’environnement et garantissant une sécurité alimentaire soutenue par la diversification des productions et des revenus qu’ils procurent, les systèmes agroforestiers apparaissent comme un modèle prometteur d’agriculture durable dans les pays du Sud les plus vulnérables aux changements globaux. Cependant, ces systèmes agroforestiers ne peuvent être optimisés qu’à condition de mieux comprendre et de mieux maîtriser les facteurs de leurs productions. L’ouvrage présente un ensemble de connaissances récentes sur les mécanismes biophysiques et socio-économiques qui sous-tendent le fonctionnement et la dynamique des systèmes agroforestiers. Il concerne, d’une part les systèmes agroforestiers à base de cultures pérennes, telles que cacaoyers et caféiers, de régions tropicales humides en Amérique du Sud, en Afrique de l’Est et du Centre, d’autre part les parcs arborés et arbustifs à base de cultures vivrières, principalement de céréales, de la région semi-aride subsaharienne d’Afrique de l’Ouest. Il synthétise les dernières avancées acquises grâce à plusieurs projets associant le Cirad, l’IRD et leurs partenaires du Sud qui ont été conduits entre 2012 et 2016 dans ces régions. L’ensemble de ces projets s’articulent autour des dynamiques des systèmes agroforestiers et des compromis entre les services de production et les autres services socio-écosystémiques que ces systèmes fournissent

Spread of invasive Aedes albopictus and decline of resident Aedes aegypti in urban areas of Mayotte 2007-2010

The invasive Asian tiger mosquito, Aedes albopictus, has been established on the French overseas island of Mayotte in the Indian Ocean since 2007. Despite the presence of a resident population of Aedes aegypti, Ae. albopictus has expanded its presence in urban areas, in contrast to the pattern of invasion by this mosquito elsewhere in the world. We undertook a comparative study of the distribution and abundance of Ae. albopictus and Ae. aegypti populations between 2007 and 2010 in different types of urban landscapes to document the invasion process. Urban and suburban areas at five localities on Mayotte were selected and ten houses with mosquito-infested larval habitats on the property were located in each area. To calculate variables that might explain mosquito infestation, the areas around the houses selected were overlaid on maps with grid cells (each 25 x 25 m) and the areas inside grid cells were analyzed to define landscape characteristics (percentage of built on land and human density) that might be predictive of Ae. albopictus presence and abundance. The proportion of sites occupied by only Ae. albopictus and the relative abundance of this species relative to total Aedes larvae and pupae significantly increased between 2007 and 2010, in both urban and in rural areas. In the 2010 survey, the number of larval habitats occupied by Ae. aegypti in the sampled area decreased sharply compared to 2007. The proportion of land with paved or hard surfaces (roads, buildings, hereafter "built-up area"), the increase of urbanized areas between 2003 and 2008, and the density of human residents were all correlated with higher relative abundance of Ae. albopictus. The urban areas of Mayotte have significant amounts of vegetation even in the more densely populated areas, and this factor may have facilitated the invasion of Ae. albopictus by providing abundant adult resting sites. These findings are relevant for vector control strategies and forecasting the success of invasions of Ae. albopictus in urban areas in other countries

A novel method for estimating P&Ds related yield loss in cacao pods in the Peruvian Amazonia.

&lt;p&gt;Cacao pest and diseases (P&amp;Ds) infect and affect their hosts in specific ways, which adds complexity to study their global impact on production. Commonly, incidence is used as an indicator to evaluate P&amp;Ds, however, it does not provide any information on yield loss, whether we look at it as a loss in quantity or quality. Therefore, from an agronomic point of view, incidence is not enough to evaluate the impact and the damage of P&amp;Ds over production. By focusing on three specific P&amp;Ds (Black Pod disease, Frosty Pod Rot and the "Mazorquero", local name for the American Cocoa Pod Borer) within the P&amp;D complex that affect the cocoa pod in the Peruvian Amazonia, this research aims to produce a simple and replicable model that will allow to estimate more accurately the P&amp;Ds incidence related yield loss and help us simulate different scenarios to calculate crop loss under different market situations. To evaluate the amount of damage caused by these P&amp;Ds, 30 pods were opened per monitored P&amp;Ds (each set infected with either one or a combination of the P&amp;Ds outlined above), totalling 120 pods for the four evaluated P&amp;Ds combinations on the CCN-51 cacao variety. Then the seeds were counted and classified in Healthy (unaffected), Affected (affected by disease but still usable) and Destroyed (unusable due to disease) to establish a Seed Damage Ratio (SDR) for each disease and disease combination. Furthermore, we elaborated a model that combines the SDRs and P&amp;D's incidence per plot to have an estimation of the yield loss at plot scale. Our results show that the Black Pod and the Mazorquero, as well as their combination, tend to cause the least amount of damaged seeds, while the Frosty Pod Rot tends to cause the most damage. Black Pod and Mazorquero tend to have similar impact, showing mixed results between healthy and usable seeds, while their combination has a bigger impact with more usable than healthy seeds. By modifying the yield loss model for the plot, two simulations of different scenarios predicting the crop loss were elaborated. These showed that the P&amp;D composition is highly relevant for crop loss estimation and the SDRs allow to take into consideration this composition for integrated P&amp;D management.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Keywords&lt;/strong&gt;: Pest and Diseases; Incidence; Yield Loss; Seed Damage Ratio.&lt;/p&gt