Mosquitoes, small flying insects, are often perceived as bothersome pests, with their bites a familiar annoyance worldwide. This raises a biological question: are mosquitoes, by definition, considered “invasive species”? Understanding this requires examining what makes a species invasive and how certain mosquito species fit this category.
What Makes a Species Invasive?
An invasive species is a non-native organism that causes or is likely to cause harm to an ecosystem, the economy, or human health. The three defining criteria for an invasive species are its non-native origin, its introduction to a new environment, and the negative impacts it subsequently produces. Not all non-native species become invasive; many non-native plants and animals, like common agricultural crops or livestock, provide benefits and integrate without causing harm. Only those that spread rapidly and inflict demonstrable damage qualify for the invasive label.
Mosquitoes: A Native Perspective
Most mosquito species are native to the environments they inhabit, with over 3,500 distinct species worldwide, found on every continent except Antarctica. Within their native ecosystems, these mosquitoes fulfill various ecological roles. Mosquito larvae, which develop in water, serve as a food source for fish, amphibians, and other aquatic insects. Adult mosquitoes primarily feed on plant nectar, making them accidental pollinators for various plants. In their natural ranges, mosquitoes are an integral part of the food web and contribute to ecological balance.
When Mosquitoes Cross Borders: Examples of Invasive Species
While most mosquitoes are native, some species have become invasive after being introduced to new regions. Aedes aegypti, commonly known as the yellow fever mosquito, originated in Africa. This species spread globally via human activities and international trade, becoming a common invasive species found in tropical, subtropical, and temperate areas worldwide.
Aedes albopictus, or the Asian tiger mosquito, is another species native to tropical and subtropical Southeast Asia. Over the past few centuries, this mosquito has spread to numerous countries across North and South America, Europe, Africa, and the Caribbean. Its global expansion has been largely facilitated by the international transport of goods, notably through shipments of used tires and ornamental plants, which inadvertently carry its resilient eggs. Both Aedes aegypti and Aedes albopictus are highly adaptable, thriving in new environments and outcompeting native species, solidifying their invasive status.
Disease Transmission and Ecosystem Alteration by Invasive Mosquitoes
The invasiveness of certain mosquito species, particularly Aedes aegypti and Aedes albopictus, poses significant public health concerns as disease vectors. Aedes aegypti is a primary vector for dengue fever, yellow fever, chikungunya, and Zika virus. Similarly, Aedes albopictus transmits dengue, chikungunya, Zika, West Nile, and Japanese encephalitis viruses. The introduction of these invasive Aedes species into new geographic areas has led to outbreaks of diseases that were previously absent or rare in those regions.
These invasive mosquitoes are aggressive daytime biters, often associated closely with humans, increasing the risk of disease transmission. Beyond direct disease transmission, their presence can also lead to ecological alterations. They may compete with native mosquito species for resources and habitat, disrupting local insect populations and food webs. The widespread establishment of these invasive species underscores the need for continued surveillance and control measures to mitigate their public health and ecological impacts.