Reproductive interference between Aedes aegypti and Aedes albopictus, and its relevance to vector control techniques

Thesis

Reproductive interference is where heterospecifics engage in mating activities which do not produce viable offspring and cause a fitness cost to at least one of the species involved. Reproductive interference occurs across a wide range of taxa, including between the mosquito species Aedes aegypti and Aedes albopictus. These species are primary vectors of dengue, a flavivirus with no vaccine or specific treatment: thus, vector control is key to reducing its public health burden. Pioneering control methods rely on the release of modified mosquitoes, which deplete the wild population or replace it with mosquitoes that cannot transmit dengue. During the development of novel techniques, population dynamic frameworks are required to evaluate their efficacy. However, these models frequently omit important ecological interactions, including reproductive interference. In this thesis, I use a theoretical model to examine the combined effect of the release of modified Ae. aegypti, and reproductive interference, on coexistence between Ae. aegypti and Ae. albopictus. I find that the release ratio of self-limiting Ae. aegypti and the strength of reproductive interference act together to determine the population size of each species, and whether stable coexistence can occur. This highlights the necessity to further our understanding of reproductive interference between Ae. aegypti and Ae. albopictus. In the subsequent chapters, I do this by conducting laboratory studies examining heterospecific insemination rates and mating behaviour. In these experiments I observe that Ae. albopictus males do not inseminate Ae. aegypti females, even those from strains with no prior contact with Ae. albopictus. This contradicts the findings in previous literature, where sympatric Ae. aegypti females have evolved resistance to mating by Ae. albopictus males, and allopatric Ae. aegypti females are susceptible. Behavioural analysis of these strains suggests that Ae. albopictus males may not attempt to mate with these females. To understand this discrepancy further, and general heterogeneity in reproductive interference, I conduct a systematic literature review of reproductive interference between Aedes spp. While I find clear predictors of heterospecific insemination rates, there is also considerable unexplained variation, and key differences in experimental methods. This thesis highlights that the strength of reproductive interference impacts the efficacy of vector control techniques and varies greatly between populations of Ae. aegypti and Ae. albopictus. I suggest that standardised methods to determine the rate of heterospecific insemination should be developed, so that the validity of reproductive interference can be readily parametrised.

Authors: Vollans, M

• DOI: 10.5287/ora-vjenzegng
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: reproductive interference; mating interactions; Aedes
• Subjects: Biology; Ecology