Editing Invasive species (section)

===Species-based mechanisms===
[[File:Riesenknoeterich.jpg|right|thumb|Japanese knotweed (''[[Reynoutria japonica]]'') is considered one of the [[100 of the World's Worst Invasive Alien Species|world's worst invasive species]].]]
[[File:Ocicat-woodpecker.jpg|upright|thumb|Cats (here, killing a [[woodpecker]]) are [[Cats in Australia|considered invasive species]] in Australia and [[Cat predation on wildlife|negatively impact wildlife]] worldwide.]]

Invasive species appear to have specific traits or specific combinations of traits that allow them to outcompete [[native species]]. In some cases, the competition is about rates of growth and reproduction. In other cases, species interact with each other more directly. One study found that 86% of invasive species could be identified from such traits alone.<ref name="kolar">{{cite journal |last=Kolar |first=C.S. |year=2001 |title=Progress in invasion biology: predicting invaders|journal=[[Trends in Ecology & Evolution]] |volume=16 |issue=4 |pages=199–204 |doi=10.1016/S0169-5347(01)02101-2 |pmid=11245943|s2cid=5796978 }}</ref> Another study found that invasive species often had only a few of the traits, and that noninvasive species had these also.<ref name="kolar"/><ref name="theb">{{cite journal |last=Thebaud |first=C. |year=1996 |title=Assessing why two introduced Conyza differ in their ability to invade Mediterranean old fields |journal=Ecology |volume=77 |issue=3 |pages=791–804 |doi=10.2307/2265502 |jstor=2265502 |bibcode=1996Ecol...77..791T }}</ref><ref name="reichard">{{cite journal |last=Reichard |first=S.H. |s2cid=29816498 |year=1997 |title=Predicting invasions of woody plants introduced into North America |journal=[[Conservation Biology (journal)|Conservation Biology]] |volume=11 |issue=1 |pages=193–203 |doi=10.1046/j.1523-1739.1997.95473.x |pmc=7162396}}</ref> Common invasive species traits include fast growth and rapid [[reproduction]], such as [[vegetative reproduction]] in plants;<ref name="kolar"/><!--high [[Biological dispersal|dispersal]] ability;--><!--[[Phenotypic plasticity|Phenotype plasticity]];--><!--[[ecological competence]];--><!--[[Generalist and specialist species|generalist]];--> association with humans;<ref name="Williams">{{cite book |last=Williams |first=J. D. |year=1998 |chapter=Non-indigenous Species |title=Status and Trends of the Nation's Biological Resources |location=[[Reston, Virginia]] |pages=117–29 |publisher=[[United States Geological Survey]] |isbn=978-0-16-053285-6 |id={{DTIC|ADA368849}} }}</ref> and prior successful invasions.<ref name="ewell">{{cite journal |last=Ewell |first=J.J. |year=1999 |title=Deliberate introductions of species: Research needs – Benefits can be reaped, but risks are high |journal=[[BioScience]] |volume=49 |pages=619–630 |doi=10.2307/1313438 |jstor=1313438 |issue=8 |doi-access=free |bibcode=1999BiSci..49..619E }}</ref> [[Domestic cat]]s are effective predators; they have become feral and invasive in places such as the [[Florida Keys]].<ref name="Cove Gardner 2018">{{cite journal |last1=Cove |first1=Michael V. |last2=Gardner |first2=Beth |last3=Simons |first3=Theodore R. |last4=Kays |first4=Roland |last5=O'Connell |first5=Allan F. |s2cid=3536174 |date=February 1, 2018 |title=Free-ranging domestic cats (''Felis catus'') on public lands: estimating density, activity, and diet in the Florida Keys |journal=[[Biological Invasions]] |volume=20 |issue=2 |pages=333–344 |doi=10.1007/s10530-017-1534-x|bibcode=2018BiInv..20..333C }}</ref>

An introduced species might become invasive if it can outcompete native species for resources. If these species evolved under great [[Competition (biology)|competition]] or [[predation]], then the new environment may host fewer able competitors, allowing the invader to proliferate. [[Ecosystem]]s used to their fullest capacity by native species can be modeled as [[zero-sum]] systems, in which any gain for the invader is a loss for the native. However, such [[unilateral]] competitive superiority (and extinction of native species with increased populations of the invader) is not the rule.<ref name="Schell"/><ref name="sax">{{cite journal |last1=Sax |first1=Dov F. |last2=Gaines |first2=Steven D. |last3=Brown |first3=James H. |title=Species Invasions Exceed Extinctions on Islands Worldwide: A Comparative Study of Plants and Birds |journal=The American Naturalist |date=December 2002 |volume=160 |issue=6 |pages=766–783 |doi=10.1086/343877 |pmid=18707464 |s2cid=8628360 }}</ref> 

[[File:Lantana Invasion of abandoned citrus plantation Sdey Hemed Israel.JPG|right|thumb|upright=1.8|[[Lantana]], abandoned [[citrus grove|citrus]], [[Sdei Hemed]]]]

An invasive species might be able to use resources previously unavailable to native species, such as deep water accessed by a long [[taproot]], or to live on previously uninhabited soil types. For example, [[Aegilops triuncialis|barbed goatgrass]] was introduced to [[California]] on [[serpentine soil]]s, which have low water-retention, low nutrient levels, a high [[magnesium]]/[[calcium]] ratio, and possible [[Heavy metal (chemistry)|heavy metal]] toxicity. Plant populations on these soils tend to show low density, but goatgrass can form dense stands on these soils and crowd out native species.<ref>{{cite journal |last1=Huenneke |first1=Laura Foster |last2=Hamburg |first2=Steven P. |last3=Koide |first3=Roger |last4=Mooney |first4=Harold A. |last5=Vitousek |first5=Peter M. |title=Effects of Soil Resources on Plant Invasion and Community Structure in Californian Serpentine Grassland |journal=Ecology |date=1990 |volume=71 |issue=2 |pages=478–491 |doi=10.2307/1940302 |jstor=1940302 |bibcode=1990Ecol...71..478H }}</ref>

Invasive species might alter their environment by releasing chemical compounds, modifying [[abiotic]] factors, or affecting the behaviour of [[herbivore]]s, impacting on other species. Some, like ''[[Bryophyllum daigremontianum|Kalanchoe daigremontana]]'', produce [[allelopathy|allelopathic compounds]] that inhibit competitors.<ref name="HERRERAFERRER-PARIS2018">{{cite journal |title=An Invasive Succulent Plant (Kalanchoe daigremontiana) Influences Soil Carbon and Nitrogen Mineralization in a Neotropical Semiarid Zone |journal=[[Pedosphere]] |volume=28 |issue=4 |year=2018 |pages=632–643 |doi=10.1016/S1002-0160(18)60029-3 |last1=Herrera |first1=Ileana |last2=Ferrer-Paris |first2=José R. |last3=Benzo |first3=Diana |last4=Flores |first4=Saúl |last5=García |first5=Belkis |last6=Nassar |first6=Jafet M. |bibcode=2018Pedos..28..632H |hdl=1959.4/unsworks_64013 |s2cid=104843296|url=https://unsworks.unsw.edu.au/bitstreams/12acbbad-8af9-444b-a478-e7dc9d941d9b/download |hdl-access=free }}</ref> Others like ''[[Stapelia gigantea]]'' [[ecological facilitation|facilitate]] the growth of seedlings of other species in arid environments by providing appropriate [[microclimate]]s and preventing herbivores from eating seedlings.<ref>{{cite journal |last1=Herrera |first1=Ileana |last2=Ferrer-Paris |first2=José R. |last3=Hernández-Rosas |first3=José I. |last4=Nassar |first4=Jafet M. |title=Impact of two invasive succulents on native-seedling recruitment in Neotropical arid environments |journal=[[Journal of Arid Environments]] |date=2016 |volume=132 |pages=15–25 |doi=10.1016/j.jaridenv.2016.04.007 |bibcode=2016JArEn.132...15H}}</ref>

Changes in [[fire regime]]ns are another form of facilitation. ''[[Bromus tectorum]]'', originally from Eurasia, is highly fire-adapted. It spreads rapidly after burning, and increases the frequency and intensity of fires by providing large amounts of dry [[detritus]] during the fire season in western North America. Where it is widespread, it has altered the local fire regimen so much that native plants cannot survive the frequent fires, allowing it to become dominant in its introduced range.<ref name="Brooks 2004 677–688">{{cite journal |last1=Brooks |first1=Matthew L. |last2=D'Antonio |first2=Carla M. |last3=Richardson |first3=David M. |last4=Grace |first4=James B. |last5=Keeley |first5=Jon E. |last6=DiTOMASO |first6=Joseph M. |last7=Hobbs |first7=Richard J. |last8=Pellant |first8=Mike |last9=Pyke |first9=David |title=Effects of Invasive Alien Plants on Fire Regimes |journal=BioScience |date=2004 |volume=54 |issue=7 |pages=677 |doi=10.1641/0006-3568(2004)054[0677:EOIAPO]2.0.CO;2 |s2cid=13769125 |doi-access=free }}</ref>

[[Ecological facilitation]] occurs where one species physically modifies a habitat in ways advantageous to other species. For example, [[zebra mussel]]s increase habitat complexity on lake floors, providing crevices in which [[invertebrate]]s live. This increase in complexity, together with the nutrition provided by the waste products of mussel [[filter feeder|filter-feeding]], increases the density and diversity of [[Benthic zone|benthic]] invertebrate communities.<ref name="silv">{{cite journal |last1=Silver Botts |first1=P. |last2=Patterson |first2=B.A. |last3=Schlosser |first3=D. |year=1996 |title=Zebra mussel effects on benthic invertebrates: Physical or biotic? |journal=[[Journal of the North American Benthological Society]] |issue=2 |volume=15 |doi=10.2307/1467947 |jstor=1467947 |pages=179–184 |s2cid=84660670 }}</ref>

Introduced species may spread rapidly and unpredictably.<ref>{{Cite book |last=Keddy |first=Paul A. |url=https://books.google.com/books?id=ncloDgAAQBAJ&q=Plant+Ecology |title=Plant Ecology |publisher=Cambridge University Press |year=2017 |isbn=978-1-107-11423-4 |pages=343 |access-date=October 6, 2020 |archive-date=August 16, 2021 |archive-url=https://web.archive.org/web/20210816224645/https://books.google.com/books?id=ncloDgAAQBAJ&q=Plant+Ecology |url-status=live}}</ref> When [[Population bottleneck|bottlenecks]] and [[founder effect]]s cause a great decrease in the population size and may constrict [[genetic variation]],<ref>{{Cite journal |last1=Xu |first1=Cheng-Yuan |last2=Tang |first2=Shaoqing |last3=Fatemi |first3=Mohammad |last4=Gross |first4=Caroline L. |last5=Julien |first5=Mic H. |last6=Curtis |first6=Caitlin |last7=van Klinken |first7=Rieks D. |date=September 1, 2015 |title=Population structure and genetic diversity of invasive Phyla canescens: implications for the evolutionary potential |journal=[[Ecosphere (journal)|Ecosphere]] |volume=6 |issue=9 |pages=art162 |doi=10.1890/ES14-00374.1 |doi-access=free}}</ref> the individuals begin to show additive variance as opposed to epistatic variance. This conversion can lead to increased variance in the founding populations, which permits [[rapid evolution]].<ref name="Prentis 2008 288-294">{{cite journal |last=Prentis |first=Peter |title=Adaptive evolution in invasive species |journal=[[Trends in Plant Science]]|volume=13 |issue=6 |pages=288–294 |doi=10.1016/j.tplants.2008.03.004 |pmid=18467157 |year=2008|bibcode=2008TPS....13..288P |hdl=10019.1/112332 |hdl-access=free }}</ref> Selection may then act on the capacity to disperse as well as on physiological tolerance to new stressors in the environment, such as changed temperature and different predators and prey.<ref name="Eunmi 2002 386-391">{{cite journal |last=Lee |first=Carol Eunmi |title=Evolutionary genetics of invasive species |journal=[[Trends in Ecology & Evolution]]|volume=17 |issue=8 |pages=386–391 |doi=10.1016/s0169-5347(02)02554-5 |year=2002}}</ref> 

Rapid adaptive evolution through intraspecific phenotypic plasticity, [[Exaptation|pre-adaptation]] and post-introduction evolution lead to offspring that have higher fitness. Critically, plasticity permits changes to better suit the individual to its environment. Pre-adaptations and evolution after the introduction reinforce the success of the introduced species.<ref name="Zenni 2013 635-644">{{cite journal |last=Zenni |first=R.D. |title=Adaptive Evolution and Phenotypic Plasticity During Naturalization and Spread of Invasive Species: Implications for Tree Invasion Biology |journal=[[Biological Invasions]] |year=2013 |volume=16 |issue=3 |pages=635–644 |doi=10.1007/s10530-013-0607-8 |s2cid=82590}}</ref>

The [[enemy release hypothesis]] states that evolution leads to ecological balance in every ecosystem. No single species can occupy a majority of an ecosystem due to the presences of competitors, predators, and diseases. Introduced species moved to a novel habitat can become invasive, with rapid population growth, when these controls do not exist in the new ecosystem.{{r|amstutz2018}}