Closely related to your quiz

https://www.researchgate.net/post/Is_there_a_point_at_which_an_invasive_species_becomes_native

Dear Rashid,

Please have a look at these links.

https://www.researchgate.net/post/Can_a_native_plant_species_be_referred_to_as_Invasive

http://www.ecobeneficial.com/ask_ecobeneficial/can-native-plants-be-invasive/

Good luck

Yes there are times (though not very common) when a native species can become suddenly large in population and spread. In the US blackberry and Typha cattails are often cited as a couple of examples. There is often some agent that has caused change to a system when this happens, for example a disturbance, change in edaphic conditions, etc.

Yes, there are species such as Limnobium spongia in the USA that are considered to be a nuisance even in its native range.

If you read about our restoration of Michael Shaw's 74 acres in California at http://www.ecoseeds.com/shaw.pdf we started with only 1% native understory cover, and it is now 95% native cover, and that all came from dormant native seeds that were in the soil underneath the natives. 

How you can look at native plants that look "invasive" you might be working in a destroyed native ecosystem, and a native species can spread rapidly to fill empty niches where other plant families should be in those spots.

The good thing about "invasive" looking natives is that they can also be "place-savers" to keep exotic plants from occupying those spaces.

However, when an area is 95% or better native cover, then the issue of diversity comes into play.  When we finished Michael Shaw's project, Michael said that getting rid of the weeds was easy, it was maintaining the native diversity that was difficult.  

An extreme case of a native plant looking invasive are the tarweed barrens in the Rocky Mountains that range for 1,000 miles from Montana to New Mexico.  At 7,000-8.000 feet there was a tall-forb community prior to the 1800s, comprising 100 species of natives, and everything was eaten by the sheep and cattle, down to the single species of tarweed.  The tarweed spread to fill in all of the empty niches and forms a monoculture across thousands of acres of the Rocky Mountains.

Since 1912, three generation of researchers were trying to plant something else in the tarweed barrens, and I had the only success in 1997 with a native needlegrass planting in the Franklin Basin of Idaho in the National Forest.  Those researchers mistook the tarweed as an invasive plant for 85 years, but what I found was it is a  "default weed".  

"Default weed" means that the tarweeds grew there because along with the vegetation, the cows and sheep walked away in their bellies the soil nutrients that other plants needed to survive as seedlings.  Without adding the proper nutrients, the tarweed would be remain to be the lone "invasive" plant for many hundreds or thousands of years.

This so-called "invasive" name that is usually attached to exotic plants, I sort into two basic categories, 1.) They are filling empty niches when the native plants have become spatially extinct, and 2.) Soil nutrient levels have dropped below what is needed by the desired plants, so the weeds are once again become the "default plants".

I have done several paintings recently on these two issues--Spatial Extinction, and the soil nutrient thresholds needed by the desirable plants.  When key nutrient levels drop below the thresholds, then the weeds come in and look like "invasives" by default. See http://www.ecoseeds.com/art4.html

We probably should stop calling both exotic plants and native plants "invasive" and instead  try to determine why there are there in the first place, like destroyed ecosystems or lack of soil nutrients that are needed by the plants that we desire?

http://www.ecoseeds.com/art4.html

Mark Julian, is it the nuisance from Limnobium spongia that makes is considered invasive?

Thanks the RG family for the responses.

Hi James Byers,

When a native species exhibited characteristics as you've mentioned, i.e disturbance and change in edaphic conditions, does these qualities qualifies it to be invasive?

It is the (rapid) spread which causes it to be called invasive. That is, the fact that it can invade.  Nuisance characteristics (better referred to as impact) are often associated or correlated with spread because Impact = Abundance x Range x Per Capita effect (Parker et al 1999). As a species invades, its range and likely it abundance too are increasing (sometimes quite rapidly).

There are two statutory definitions of “invasive species” that have been in place for some time (see following). That there is some confusion with the term is due to popular media, particularly arising from (a) false balance, (b) conflict-driven reporting, and (c) a pervasive ignorance/avoidance of science. A native species may exhibit “weedy” characteristics, but as noted in previous comments, this is a result of human land management activities. Climate change will exacerbate the problems of both invasive alien species and native weedy species in the short term; however, research indicates that IAS will be dominant in the long term.

Invasive species are plants, animals, or pathogens that are non-native (or alien) to the ecosystem under consideration and whose introduction causes or is likely to cause harm. [emphasis added]

As per [USA] Presidential Executive Order 13112 an “invasive species” is defined as a species that is: 1) non-native (or alien) to the ecosystem under consideration and 2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health. Invasive species can be plants, animals, and other organisms (e.g., microbes). Human actions are the primary means of invasive species introductions. https://www.invasivespeciesinfo.gov/whatis.shtml

An invasive alien species (IAS) is a species that is established outside of its natural past or present distribution, whose introduction and/or spread threaten biological diversity.

An alien species is a species introduced by humans – either intentionally or accidentally – outside of its natural past or present distribution; however, not all alien species have negative impacts, and it is estimated that between 5% and 20% of all alien species become problematic. It is these species that are termed ‘invasive alien species’ (IAS). Convention on Biological Diversity https://www.iucn.org/theme/species/our-work/invasive-species

Invasive alien species are plants, animals, pathogens and other organisms that are non-native to an ecosystem, and which may cause economic or environmental harm or adversely affect human health. In particular, they impact adversely upon biodiversity, including decline or elimination of native species – through competition, predation, or transmission of pathogens – and the disruption of local ecosystems and ecosystem functions. https://www.cbd.int/idb/2009/about/what/

There are invasive alien species (IAS) and non-invasive alien species. Many cultivated crops are found in the latter category. Other "non-invasive" alien species could better be termed "not-yet-invasive" due to unknown factors such as propagule pressure, lag time, climate change, etc. Precise terminology matters beyond just science. The ISSG blog [www.issg.org/about_is.htm] has some good articles about how muddled language can distract people from the fact that IAS are a serious threat to biodiversity.

This is partly just semantics, i.e. to do with how we use words. This isn't biology. On the other hand, describing a native that rapidly expands its population like an IAS does as an 'invasive native' can be useful, since such species may require the same management response. However, an invasive native has presumably coevolved with the local flora and fauna, and will support many native herbivores, microbes, mutualists etc., while an invasive native is likely to support fewer other species. So invasive natives should usually (always?) be preferred to invasive aliens.

Thanks Ruark Clearly for the elaborate differentiation of Invasive alien species, and non-invasive alien species. Whats your conclusion with respect to the question?

There may be a possibility to native become invasive, under changing conditions like  climatic conditions variation, changing reproductive fecundity of species, genetic variations and due to human  disturbances to native habitats. But after sometimes there may be a possibility of change in species inversion curves and again native in a equilibrium with other species.  .

Hello

As R. T. Corlett ·says above, a native species "has presumably coevolved with the local flora and fauna, and will support many native herbivores, microbes, mutualists". So I believe that is precisely why we should differentiate invasive from "native invasive" species, personally I prefer the term expansive to designate a native species that rapidly expands its population, from an actual invasive species.

Straight from Wikipedia [https://en.wikipedia.org/wiki/Typha] "Although Typha are native wetland plants, they can be aggressive in their competition with other native species.[9] They have been problematic in many regions in North America, from the Great Lakes to the Everglades.[7] Native sedges are displaced and wet meadows shrink, likely as a response to altered hydrology of the wetlands and increased nutrient levels." [emphasis added]

This is a description of a native species that can become a "pest" under certain (almost always anthropogenic) conditions. No need to invoke the "invasive native" label. Cattails are an important wildlife and cultural resource. Under natural conditions, this species functions as an integral component of a healthy ecosystem.

This is more than just semantics. If we call Typha (some 30 spp.) a "sometimes invasive native," how does that inform anyone about management of each individual species, or the genus as a whole? Further, by invoking a statutory term ("invasive"), you will confuse anyone who is outside (and even some inside) of the regulatory and scientific communities. This includes public officials who, driven by public outcry, may attempt to divert funds from managing true invasive species to instead manage the "invasive native" of the day.

In the case of Florida, there is an invasive aquatic plant control program and an invasive terrestrial plant control program. The aquatic plant program has a larger remit that includes navigation, flood control, and recreational access. Thus, control efforts may be directed at native pest plants that interfere with such activities. The terrestrial plant program is statutorily restricted to managing only invasive species. Although I do get occasional requests to control "invasive" oaks (succession driven by lack of fire) and titi (Cyrilla racemiflora L.; also fire exclusion and past land management practices). And this from people who should know better (see preceding paragraph).

Great Responses.

Yes. Native plant species can become invasive if the conditions for growth are altered in their favour relative to other native plants.

Thanks Prof Tsingalia.

But again these native come invasive plants will fail to meet the definition of an invasive species, which requires an invasive species to be non-native/ alien to the ecosystem under consideration.

What's your take on this?

Within the profession of Ecological Restoration, we welcome "invasive" local native species, because that means that they can colonize a disturbed area faster than the exotic plants and weeds can, so are extremely important tools for us to utilize as land-doctoring "medicines". 

Thanks CRAIG

Yes. Native plant species can become invasive if conditions of growth change drastically.

Dear Mugatsia,

Thanks for your response. Do you have any published examples for this

Sena

You want and need local native species to be "invasive" because those species act to quickly heal damages that occur within the ecosystem, like from grazing or fires, so that the ecosystem does not lose any of the soil that took hundreds of years to build up, to wind or water erosion. Just like cells move in to heal cuts to our skin, there are certain native plants that move in and start quickly repairing soil-wounds also.

Thanks for responses and ideas of you all.