Evaluating larval mosquito resource partitioning in western Kenya using stable isotopes of carbon and nitrogen

Thomas M Gilbreath,Yaw A Afrane,Eliningaya J Kweka,Andrew K Githeko,Guiyun Yan

doi:10.1186/1756-3305-6-353

Abstract

BackgroundIn sub-Saharan Africa, malaria, transmitted by the Anopheles mosquito, remains one of the foremost public health concerns. Anopheles gambiae, the primary malaria vector in sub-Saharan Africa, is typically associated with ephemeral, sunlit habitats; however, An. gambiae larvae often share these habitats with other anophelines along with other disease-transmitting and benign mosquito species. Resource limitations within habitats can constrain larval density and development, and this drives competitive interactions among and between species.MethodsWe used naturally occurring stable isotope ratios of carbon and nitrogen to identify resource partitioning among co-occurring larval species in microcosms and natural habitats in western Kenya. We used two and three source mixing models to estimate resource utilization (i.e. bacteria, algae, organic matter) by larvae.ResultsLaboratory experiments revealed larval δ13C and δ15N composition to reflect the food sources they were reared on. Resource partitioning was demonstrated between An. gambiae and Culex quinquefasciatus larvae sharing the same microcosms. Differences in larval δ13C and δ15N content was also evident in natural habitats, and Anopheles species were consistently more enriched in δ13C when compared to culicine larvae.ConclusionsThese observations demonstrate inter-specific resource partitioning between Cx. quinquefasciatus and An. gambiae larvae in natural habitats in western Kenya. This information may be translated into opportunities for targeted larval control efforts by limiting specific larval food resources, or through bio-control utilizing competitors at the same trophic level.

Highlights

In sub-Saharan Africa, malaria, transmitted by the Anopheles mosquito, remains one of the foremost public health concerns
Carbon and nitrogen isotopic signatures of Cx. quinquefasciatus and An. gambiae larvae reared from first instar on Tetramin fish food were not significantly different (δ13C, t = 0.66, df = 4, P = 0.54; δ15N, t = 0.09, df = 4, P = 0.93) (Figure 1)
When An. gambiae first instar larvae from the same laboratory colony were reared on yeast or fish food alone, the carbon and nitrogen isotopic signatures reflected the food source (An. gambiae reared on fish food and yeast; Welch’s t-test; δ13C, t = 104.20, df = 3.0, P < 0.0001; δ15N, t = 19.97, df = 2.2, P = 0.0015) (Figure 1)

Summary

Introduction

In sub-Saharan Africa, malaria, transmitted by the Anopheles mosquito, remains one of the foremost public health concerns. Higher larval densities and competition between An. gambiae s.s. and An. arabiensis result in extended development times, and several studies indicate that this may be a direct result of increased competition for microbial food resources [3,4,5]. This is noteworthy for An. gambiae s.l. larvae, because they typically inhabit temporary, sunlit pools and increased development times may exceed the duration of aquatic habitats [6,7,8]. Minakawa found a significant correlation between habitat availability and the density of indoor resting mosquitoes in homes [6]

Methods

Results

Discussion

Conclusion