Impact of invasive weed Parthenium hysterophorus (Asteraceae) on mosquito abundance and plant-feeding behavior in an arboviral endemic region in Kenya.

BACKGROUND: Invasive alien species (IAS) are rapidly altering ecosystems, undermining biodiversity, ecosystem processes, and interspecies interactions. Although IAS ecological and economic effects are well recognised, their impact on mosquito populations and the dynamics of infectious diseases is poorly understood. Plant-derived sugars are crucial for mosquito biology, supporting nectarivorous male survival and enhancing female blood feeding.

METHODS: In this study, we investigated how Parthenium hysterophorus, a rapidly proliferating invasive weed, shapes the population structure and nectar-feeding behaviour of the mosquito vector in the Rift Valley area of Kenya. Across six villages, three heavily infested with P. hysterophorus and three uninfested controls, we collected 48,489 mosquitoes representing 35 species from two subfamilies (Anophelinae and Culicinae) and nine genera, including Anopheles, Aedes, Culex, Mansonia, and Coquillettidia. Mosquito plant feeding was confirmed using the anthrone test, and the ingested flora were identified via DNA barcoding of chloroplast markers, specifically matK, rbcL, and ITS2.

RESULT: Mosquito abundance was significantly higher in Parthenium-infested villages, particularly during the dry season (p < 0.001), despite similar species diversity across sites. Medically important vectors, including Mansonia africana, Coquillettidia metallicus, Culex pipiens, and Anopheles funestus, were notably more common in invaded habitats. Overall fructose positivity was significantly high in mosquitoes from Parthenium sites (p = 0.046), with females showing especially higher rates (28.1% vs 18.0%; p = 0.0038). DNA barcoding indicated a clear feeding preference for P. hysterophorus among Coq. metallicus, Mn. africana, and An. funestus, alongside other plants such as Lantana camara.

CONCLUSION: Our findings indicate that P. hysterophorus has a notable impact on mosquito population composition and stimulates sugar-feeding behavior among important vector species. This IAS acts as a sustainable nutritional source, potentially enhancing mosquito survival, extending vector activity in dry seasons, and heightening the risk of arboviral disease transmission. The findings highlight the critical need to integrate invasive plant management within comprehensive mosquito control strategies.