The oxymoron of Local Invasive Species – Issue #67

Hello Explorer,

Some species are known to cause havoc when they are introduced into a habitat or area where they do not naturally occur. Species such as this are only classified as invasive species if they can displace local species that utilize the same habitat, resulting in a loss of biodiversity and potentially ecological functionality within the ecosystem. Eradicating invasive species through whichever means necessary is usually quite clearcut. They are killing or forcing local species to move, endangering the local species existence, thus the invasive species must be eradicated, restricted from dispersal, or controlled, usually at whatever means necessary is economically viable.

Something that is not as commonly seen and much more complex, are local invasive species. Local invasive species does at first seem like a contradicting statement to make, because how can a native and naturally occurring local species be invasive?

These local invasive species, such as the African Big-headed Ant (Pheidole megacephala) and the Small Black Sugar Ant (Lepisiota capensis), have the ability to displace other local species and potentially even to disrupt ecological processes within its natural range. The control methods are thus much more complex, as it is a naturally occurring species. Total eradication is completely out of the question. Restricting dispersal could negatively impact the species as it is within its natural range. Controlling the species could impact ecological processes that we do not know that they are a part of.

Local invasive species are often also pests within their natural range, due to their resilience to adapt to any habitat including agricultural and cosmopolitan areas. Thus, controlling such species within an agricultural or urban (within your home or in a building) setting is usually the same as we deal with invasives. Use chemical control methods to eradicate the species before it causes damage.

Wider scale control, however, is not as clear cut. A friend and myself had the discussion around controlling specifically the African Big-headed Ant and the Small Black Sugar Ant. The idea that was put forward was to mass capture queens for the two species during their nuptial flights and then destroy them humanely. The problem, however, is that this may have an unseen negative impact on the natural population, which could lead to an ecological knock-on effect.

The African Big-headed Ant has a cyclical population, during winter their populations become massive and they are everywhere, while in summer you struggle to find a single colony. I have observed them feasting on many insects during winter that succumbs to the cold nights. They along with the Small Black Sugar Ant are also much more active than any other ant species during winter, as most other species enter either dormancy or partial dormancy.

The Small Black Sugar Ants on the other hand, I have found in great numbers throughout the year with a near constant population. I have seen in natural areas that their presence can overwhelm an area, where you will almost exclusively find Small Black Sugar Ants. After observing the same areas over a year, I have, however, found that the presence of the Small Black Sugar Ant is cyclical, sometimes they are present in huge numbers and after given sufficient time there won’t be any sign of them being in the area. Thus, I hypothesis that they might serve as an ecological reset, a species that displaces all of the species that occupy a similar niche, preventing one species from gaining the upper hand and forming a monotypic niche diversity. Simply put, they prevent one species from dominating an area and permanently excluding other species that utilize the same niche.

Thus, if both of these local invasive species serve an ecological purpose within its natural range, any attempts to eradicate, restrict or control such a species could end in a much greater ecological disaster. Do note that this is within natural areas with in tact natural ecosystems, and not within agricultural or cosmopolitan ecosystems.

Due to the abundance of food and the variety of food sources available within both agricultural and cosmopolitan areas these species will gain uncontrollable population sizes and cause significant economical damage if they are not controlled.

The main question that remains is, how far should the control of a locally invasive species go? Should we limit it to control methods that are contained to agricultural and cosmopolitan areas? Should we use any control methods that can potentially impact natural populations in any way, such as mass trapping?

If you would like to send me a message with your answers, feel free to do so on Instagram @abugmanslife or via email to [email protected].

Weekly Top Shot: Food!