Oviposition site attraction of Aedes albopictus to sites with conspecific and heterospecific larvae during an ongoing invasion in Medellín, Colombia.

Background: Aedes aegypti and Aedes albopictus are two globally invasive vectors with similar ecological niches. Encounters between them can result in either competitive exclusion or stable co-existence, but it is unclear what drives these variable outcomes. Larval competition in favor of Ae. albopictus is a main hypothesis for the competitive exclusion of Ae. aegypti observed in some regions. However, the role of oviposition preference in determining the degree of competitive larval interactions in the field is not well understood. In this study, we used a combination of mark-release-recapture methods with ovitraps in the open-field and a semi-field cage to test whether gravid Ae. albopictus seek oviposition sites in response to the presence, species, and density of either conspecific or heterospecific Ae. aegypti larvae in the aquatic habitat. We conducted our study in Medellín, Colombia, where Ae. aegypti is a long-term resident and Ae. albopictus is a recent invader.
Results: In the open-field and semi-field cage experiments, gravid Ae. albopictus showed strong preference for ovitraps with larvae over those without. They consistently preferred ovitraps with higher density of conspecific (Ae. albopictus) larvae and low density of heterospecific (Ae. aegypti) larvae over traps with no larvae or high density of heterospecific (Ae. aegypti) larvae. In the semi-field cage experiment, traps with low density of Ae. albopictus were not preferred more or less than any other trap, but in the open-field experiment they were preferred over traps without larvae.
Conclusions: We demonstrate, through open-field and semi-field cage experiments, that Ae. albopictus are more attracted to oviposition sites with larvae and that the combination of species and density of larvae influence attraction. This demonstrated preference could increase interspecific larval competition as Ae. albopictus actively seek containers with conspecific and heterospecific larvae. Any resulting competition with Ae. aegypti may favor one species over the other and alter the distribution or abundance of both. Because these species vary in vectorial capacity and insecticide resistance, effects of interspecific competition could ultimately impact arbovirus transmission rates and the success of vector control efforts .