Species Extinction and Invasive Species

Since my project is about what makes one ficus species invasive and what makes another at high risk of extinction, it would be good to first discuss what is invasiveness and what is extinction. :)

I am reading "Essentials of Ecology" by G. Tyler Miller, Jr. (2007) Fourth Edition. Thomson Learning. It is a good textbook for fun and casual, layperson reading. A lot of beautiful pictures and not very dense in content, straightforward and simple. In stark contrast to another textbook - Ecology, Concepts & Applications by Manuel C. Molles, Jr. that is very text dense.

Species Extinction

There are three types of extinction. Local extinction occurs when a species is no longer found in an area but is still found elsewhere in the world. Ecological extinction occurs when so few members of a species are left that the remaining members are no longer able to perform their ecological functions in their communities. Biological extinction occurs when a species is no longer found on planet earth. Biological extinction is permanent!

Besides being extinct, a species can also be endangered or threatened. An endangered species has so few individual survivors that it could soon become extinct; while a threatened species (aka vulnerable species) is still abundant in its natural range but is declining in numbers and could soon be endangered and/or extinct.

Certain characteristics predisposes a species to extinction. These characteristics could be innate, for example a low reproductive rate or dependent on external factors such as presence of predators and pollinators.

The International Union for the Conservation of Nature and Natural Resources (IUCN) - also known as the World Conservation Union publishes annual Red Lists, which is a list of the world's threatened species. This is where I go to to find my threatened ficus species.

"Scientists also use models to estimate the risk of a particular species becoming endangered or extinct within a certain period of time, based on factors such as trends in population size, changes in habitat availability, interactions with other species, and genetic factors."

Is this what I'm doing?

Invasive Species

There are two types of introduced species: deliberately introduced species and accidentally introduced species. Deliberately introduced species are nonnative species that are brought in to provide food, medicine and other benefits. For example, ficus species are very popular ornamental plants. They are thought not be spread, due to their need to specific wasps as pollinators. However, wasps can travel as well and many ornamental figs have become weeds. Accidentally introduced species are unwanted guests that come in many ways. Wild pets might escape peoples' homes. Cargo ships discharge their ballast water containing nonnatives. Earthworms hide among soil when vegetables are shipped. Our local infamous changeable lizards take the Malayan Railway from Thailand to Tanjong Pagar railway station.

There also is a distinction between alien species and invasive species. I believe only when an alien/nonnative species invades an ecosystem, then they are considered invasives.

Such invasive species are called weeds, though a weed is not necessarily invasive. I believe a weed is any unwanted plant. There is a quote that goes "a weed is but an unloved flower" but this is likely a romanticized statement. To ecologists and conservationist, a weed, if its invasive, is a ruthless invader that should be eliminated at all costs. For me, I get my ficus weed species from The Global Compendium of Weeds.

So here is a short introduction to this enormously large topic! :)