Diagnostic Characteristics taken from ÔIdentifying native and alien crayfish species in EuropeÕ, a key produced as part of the European CRAYNET project (Pšckl et al., 2006)
B. canadensis in its non-native range is a large goose with a dark brown body, black head and neck and white cheeks. Its honking call is very loud and easily recognised. Within the natural range, some races are no larger than the snow goose Anser caerulescens (Chen caerulescens) and there is considerable variation in plumage tones. For more details, see for example Kear (2005).
P. parva populations occurring in European fresh waters display a wide morphological variability, significantly differing from one another (Kotusz and Witkowski, 1998;Z‡horsk‡ et al., unpublished). However, there appears to be little variability amongst introduced European populations, with the greatest morphological variation appearing to be between native and non-native populations (Louette et al., 2002). The species is generally saline intolerant (Scott et al., 2007) and is known to disappear from fresh waters that suffer rises in salinity Sexual dimorphism is manifested in larger body size of males as well as in four plastic characters (Coombs, 2004). Large adults have sexually dimorphic coloration (Kottelat, 2001). The body colour is greenish-grey and brown in the back. Lateral line runs along the centre of body and contains 35-38 scales. P. parva has a total of 3-3 dorsal spines and 7-7 dorsal rays whereas anal spines and anal rays are 3-3 and 6-6, respectively. Mouth is transverse and positioned superiorly. It does not have barbels. P. parva can grow to a total length of 11 cm (Berg, 1964).
Adapted from Flora Zambesiaca (2014)
C. asiatica is a low-growing perennial with a pan-tropical distribution. It can spread to form a dense ground cover, desirable in some situations but unwelcome in others. It is recorded as invasive in a number of Pacific islands to which it has been introduced and is classed as High Risk (score 7) by PIER (2014), but the situations in which it is causing problems are not clear. It is not especially competitive in crops but may affect wild vegetation and biodiversity. C. asiatica is also among a number of species invasive in the Dongting Lake wetlands, Hunan province, China (Hou et al., 2011).
C. asiatica is recorded as a weed in rice paddies, various plantation crops and forestry, but there are no indications of serious crop loss due to C. asiatica. Where it is listed as invasive, some native species are being impacted but little detail has been seen. In Hawaii, C. asiatica is among introduced species which have contributed to the decline of native sedges Carex thunbergii and Carex echinata (University of Hawaii, 1991).
Following Hong (1993) and Alaska Natural Heritage Program (2011)
Persicaria wallichii is a shrubby perennial herb up to 180 cm tall that originates from the temperate, western regions of Asia and the Indian subcontinent. It is naturalized in Europe, Canada and the United States, where it was introduced as a garden ornamental. It grows vigorously and creates large and dense stands that exclude native vegetation and prevent tree seedlings from growing. P. wallichii can greatly alter natural ecosystems and promotes the erosion of river banks. It is reported as invasive in its native range in northern India (Kala and Shrivastava, 2004), as well as in its non-native range in Belgium and the UK (Rich and Woodruff, 1996;Branquart et al., 2007). In the western USA it is a declared noxious weed in the states of Montana, California, Washington and Oregon (USDA-NRCS, 2015).
The following has been adapted from Wilken and Hannah (1998), Hoban and Hoshovsky (2000), Flora of North America (2016) and the Encyclopedia of Life (2016).
E. glomerata is a perennial herbaceous plant in the Asteraceae that is native to Australia and New Zealand and has become naturalised in northwestern USA (in the states of Washington, Oregon and California). It is considered a problem invader in the Channel Islands, California, USA. It is able to quickly colonise and dominate disturbed areas such as those cleared by logging activity or fire. Along with other non-natives, it is potentially threatening native species in California.
L. morrowii is a deciduous, woody shrub with hollow stems and brown or grey bark that is ridged and peels off easily (Go Botany, 2018). It grows up to 2.4 m tall (Invasive.org, 2018). It has simple, untoothed, elliptical or oblong leaves that are 25-50 mm long, with two leaves per node (Go Botany, 2018). Leaves are hairy underneath and hairless or sparsely hairy on the upper surface (Go Botany, 2018). They are greyish and tomentose on the lower surface (IPANE, 2018) and have one main vein running from the base towards the tip, with secondary veins branching off at intervals (Go Botany, 2018). Peduncles are 5-15 mm and very hairy, and bractlets, sepals and corolla are also covered in downy hair (IPANE, 2018). Winter buds have three or more scales that overlap like shingles, with one edge covered and the other exposed (Go Botany, 2018).
Lonicera morrowii is a deciduous, woody shrub, native to Japan, China and the Republic of Korea. It was introduced to the USA from Japan in the 1860s as an ornamental, but has since escaped cultivation, is considered invasive and is prohibited in some states in the USA. It invades open woodlands, old fields and other disturbed sites, and spreads rapidly due to seed dispersal by birds and mammals. It can form a dense understory thicket which restricts native plant growth and tree seedling establishment. L. morrowii hybridizes with another non-native honeysuckle, L. tatarica, to produce L. x bella, and this plant is also considered invasive.
C. debeauxii is an erect perennial herbaceous plant growing to 80 cm tall. Young plants have a strong tap root which may develop into a tough crown of several roots as plants mature. The basal rosette leaves are entire to deeply lobed and slightly hairy;stem leaves are small and without a stalk (sessile). Growth is openly branching, stems are slender and somewhat rough to the touch.
Centaurea debeauxii, a fertile hybrid of C. nigra and C. jacea, is an invasive perennial of pasture and natural grasslands with an increasing non-native distribution in wet temperate areas of continental North America, now also recorded in South America and Australia. Favouring mesic and moist situations, it can form dense stands, outcompeting native grasses and displacing broadleaved species. It is listed as a noxious weed in several western US states as well as one Canadian province. In natural and semi-natural plant communities, it threatens rarer endemics such as the rough popcorn flower (Plagiobothrys hirtus).
A stout, erect, perennial, rhizomatous grass, up to 120 cm high. Rhizomes spreading horizontally and vertically;the younger parts of the rhizome with white coherent pith and bearing yellowish-white overlapping scale leaves;the older parts yellow-brown and hollow, the scale leaves mostly perished. Roots white and fleshy when young, becoming brownish and wiry with age, up to four per node. Aerial shoots formed mainly along the vertical rhizomes, forming dense tufts;the stems of the aerial shoots form elongated internodes when buried, thus becoming vertical rhizomes. Leaves up to 6 mm wide and 60 cm long, but sometimes as much as 90 cm long, sharply pointed, usually tightly inrolled, except under moist conditions;the abaxial surface greyish-green and smooth, without distinct ribs, the adaxial surface glaucous, closely ribbed with ribs densely and minutely hairy;sheaths overlapping. Ligule up to 2.5 cm long, acuminate, split at the top when young and usually torn when older. Panicle 7-15 cm long, dense, stout, spike-like, narrowly oblong to lanceolate-oblong, tapering upwards, whitish, branches erect. Spikelets 10-16 mm long, compressed, narrowly oblong, gaping when dry, with one floret. Glumes slightly unequal, whitish, keeled, slightly pointed, margins hyaline, keel serrate, exceeding the lemma and palea;lower glume 1-nerved, upper glume 3-nerved. Lemma lanceolate, minutely rough, 5-7-nerved, keeled, 8-12 mm long, with two short points at the top, and a short stout awn less than 1 mm long in between;surrounded at the base with fine hairs c. 1/3 of the length of the lemma. Palea 2-4-nerved, compressed, acute, keeled, shortly ciliate on the keel. Lodicules c. 1 mm long, tapering. Stamens three, 4-7 mm long, up to ten times as long as wide, hanging outside the floret. Styles short. Ovary glabrous. Grains brown, obovate, shed while still enclosed by the hardened lemma and palea (Huiskes, 1979).
A. arenaria is a grass species specially adapted to growing on sand dunes. It is native to Europe and western Asia and has been introduced as a very effective sand binder to a number of other countries but has become a problem in many of these. In the countries to which A. arenaria has been introduced it invades coastal sand dunes, thriving in areas of active sand movement. In such places it not only disturbs and replaces native vegetation but can also change the topography and composition of whole foredune systems. In the USA, it has replaced the foredune vegetation, greatly reducing biodiversity, and the foredune topography has changed to much steeper slopes and whilst dune ridges further inland used to be perpendicular to the coast they are now parallel to the coast (Russo et al., 1988). In California it is negatively impacting on a number of endangered species of plants. It is reported as a major alien invader in Australia, New Zealand and South Africa where it is also having a negative environmental impact.
In North America, A. arenaria has escaped from plantations and has become naturalized north of San Francisco where it now dominates beaches formerly dominated by Elymus mollis [ Leymus mollis ] (Russo et al., 1988). Despite L. mollis being more salt tolerant than A. arenaria, A. arenaria can withstand sand accumulation of up to 1 m per year (Willis et al., 1979).
In Australia, native beach plants most commonly affected are beach spinifex (Spinifex sericeus), beach fescue (Austrofestuca littoralis), dune sedge (Carex pumila) and glistening saltbush (Atriplex billardieri). In addition to A. littoralis and S. sericeus, in New Zealand the native species affected by the spread of A. arenaria include pingao (Desmoschoenus spiralis [ Ficinia spiralis ]) and New Zealand sea spurge (Euphorbia glauca).
Structurally, the Lemnaceae are the simplest of the flowering plants. The plants are not differentiated into stems and leaves;instead, the plants in the family have an undifferentiated leaf-like body commonly referred to as a frond. Fronds floating, 1 or 2-few, coherent in groups, obovate, flat to thickish (but not gibbous), 0.8-4 mm, 1-2 times as long as wide, margins entire and thin, usually pale green, shining, nearly always with a sharp ridge with white papillae;veins 1, sometimes indistinct, very rarely longer than extension of air spaces, not longer than 2/3 of distance between node and apex;with or without small papillae along midline;anthocyanin absent;largest air spaces much shorter than 0.3 mm;turions absent. Roots to 1.5 cm, tip rounded to pointed, one root per frond;sheath not winged. Stipes (stalks) white, small, often decaying. Flowers within membranous cup-like spathes (open on one side) inside budding pouches located on either side of the basal end. Ovaries 1-ovulate, utricular scale open on 1 side. Fruits 0.6-1 mm, not winged. Seeds with 12-15 distinct ribs (Landolt, 1980;Flora of North America, 2008;Armstrong, 2009).
L. minuta is a small free-floating plant, no more than 3 mm in length. It is widely distributed in southern and western North America and is also found in Central and South America. It occurs in lowland ditches, ponds, canals, streams and rivers, and more rarely it is found in lakes (Preston and Croft, 1997). It often forms dense mats on the surface of water, reducing the light penetration and gas exchange, often causing the disappearance of submersed aquatic plants. Outbreaks are usually limited in time and space and are favoured by eutrophication. L. minuta is introduced in Eurasia (Landolt 2000) and it was first recorded in western France in 1965. From there it has spread all over Europe as far as southern Russia and Greece. It is also present in Japan (e.g. Landolt, 1986). It is considered a casual alien by Global Compendium of Weeds (2007). In many areas it is a noxious weed, as in Belgium, and it is included in the watch list with moderate impact (Branquart et al., 2007).
H. undatus is a fast growing, epiphytic or xerophytic, vine-like cactus. Stems are triangular, 3-sided, although sometimes 4- or 5-sided, green, fleshy, jointed, many branched. Each stem segment has 3 flat wavy ribs and corneous margins may be spineless or have 1-3 small spines. Stems scandent, creeping, sprawling or clambering, up to 10 m long. Aerial roots, which are able to absorb water, are produced on the underside of stems and provide anchorage for stems on vertical surfaces. Flowers are 25-30 cm long, 15-17 cm wide, nocturnal, scented and hermaphroditic;however, some cultivars are self-compatible. Flowers are typically white in colour and bell shaped, stamens and lobed stigmas are cream coloured. Fruit is a fleshy berry, oblong to ovoid, up to 6-12 cm long, 4-9 cm thick, red with large bracteoles, pulp white, edible, embedded with many small black seeds. Average fruit weight is 350-400 g, although may weigh up to 900 g (Merten, 2002).
H. undatus is one of many alien species in Florida threatening the endangered plant species Chromolaena frustrata, Consolea corallicola and Harrisia aboriginum (US Fish and Wildlife Service, 2013).
Tree to 10 or more metres high, the branchlets usually tomentose when young. Leaves moderately large, an average leaf about 20-foliolate;petiole short, pubescent, eglandular;rachis usually about 2 dm. long, eglandular and otherwise like the petiole;leaflets several to many pairs, lanceolate, 3-8 cm. long and usually about 2 cm. wide, acute apically, obtuse basally, pubescent below, especially along the veins, puberulent to subglabrous above and less dull than below, opposite on the rachis, with 10 or more pairs of prominent lateral veins;petiolules 2-3 mm. long, pubescent. Inflorescence of several terminal or subterminal several-flowered racemes;bracts lanceolate, a few mm. long, caducous. Flowers yellow;sepals 5, obovate-orbicular, markedly unequal, up to 1 cm. long and broad, glabrous to lightly puberulent;petals 5, mostly obovate, markedly unequal, up to 2.5 cm. long and 1.5 cm. broad, subglabrous, venose, short-clawed;stamens 10, 3-morphic;the 3 lowermost the largest, their anthers oblong, about 7 mm. long, short-rostrate apically and dehiscent by terminal pores, the loculi somewhat converging terminally;anthers of 4 median stamens 5-6 mm. long, similar to the 3 lowermost except the rostrum reflexed and the loculi divergent terminally;3 uppermost stamens markedly dissimilar, more or less rudimentary, the anthers distinctly bilobed, each lobe reniform and dehiscent the length of its outer margin;ovary linear, glabrous. Legume linear, turgid-quadrangular, up to 2 dm. long and 1 cm. wide, transversely multiseptate, tardily dehiscent along one margin (Missouri Botanical Garden, 2014).
S. spectabilis is a medium to large tree from tropical America, listed in the Global Compendium of Weeds as an ‘environmental weed’, ‘garden thug’, and ‘naturalised weed’ (Randall, 2012). The species is extremely fast-growing, flowers and sets seed profusely, and re-sprouts readily when cut (Mungatana and Ahimbisibwe, 2010). In Australia it is considered naturalized, has been recorded as a weed of the natural environment and an escape from cultivation, and is labelled an invasive species, indicating its high negative impact on the environment due to its ability to spread rapidly and often create monocultures (Randall, 2007). In Uganda, the species is considered an invasive alien species with high risk to the native flora (Mungatana and Ahimbisibwe, 2010). In Singapore S. spectabilis has been identified as a casual, spontaneous exotic species that survives outside cultivation but does not form self-replacing populations, and relies on repeated introductions or limited asexual reproduction for persistence (Chong et al., 2009). The species is a cultivation escape in Trinidad and Tobago (Irwin and Barneby, 1982) and is considered an invasive species in Cuba (Oviedo-Prieto et al., 2012).
Agroforestry experiments in Kenya showed that while S. spectabilis is useful as hedges for cropping systems, if grown in semi-arid conditions S. spectabilis will out-compete crops for water uptake and suppress crop yields;in the cases recorded, grain yields of maize grown with S. spectabilis or Leucaena leucocephala were reduced by between 39% and 95% (Noordwijk et al., 2004).
A. nigrofasciata is a fairly small cichlid that grows to approximately 12 cm but more commonly to 8.5 cm in length (Page and Burr, 1991;Froese and Pauly, 2014). It is pale blue/grey in colour with approximately seven black vertical stripes/bars on the sides that extend onto the dorsal and anal fins. The vertical stripes vary in intensity and the first and third bar may appear as blotches. The first or second bar may be Y shaped. There is a black spot on the operculum. The fins are clear or light blue/grey. Large males may have intense black bars with long fin rays at rear of dorsal and anal fins (Page and Burr, 1991). Selective breeding has produced several colour variations including pink, albino, long-finned and marbled (Page and Burr, 1991).
A. nigrofasciata is a small, popular ornamental freshwater fish that is native to a number of countries in Central America. It occurs as an introduced species in the aquatic habitats of at least 10 countries, principally because of human-mediated translocation and release. Due to the popular ornamental status of A. nigrofasciata, it is rarely considered a “pest” species. Wide environmental tolerances, the ability to colonise disturbed habitats, trophic opportunism, parental care and fast growth rates all contribute to the likelihood of this species becoming invasive. Potential ecological impacts upon endemic fish fauna may include resource competition and predation of aquatic invertebrate communities as a whole. Research has suggested that A. nigrofasciata may be responsible for the displacement of native fishes in Mexico and Hawaii. Of particular note is that the species is aggressive, particularly when breeding as territories are established on the substrate and defended against all intruders.
B. distachyon is an erect annual grass. Culms geniculately ascending, or decumbent;3-40 cm long. The following is adapted from Cal-IPC (2016) and Clayton et al. (2016).
B. distachyon, commonly known as purple false brome, is a grass species that is related to the major cereal grain species. It is native to southern Europe, northern Africa and southwestern Asia east to India but is widely introduced and naturalized elsewhere. It occurs broadly as an alien species throughout North America and has been reported as invasive in China, Chile, Australia and California. Brachypodium species are invasive weeds that dominate areas where they are planted or have become established and this species can equally form dense stands, reducing diversity and preventing the establishment of native species. The California Invasive Plant Council (Cal-IPC) classifies its potential impact on native ecosystems as ‘Moderate’.
An introduced species, alien species, exotic species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived there by human activity, either deliberate or accidental. Non-native species can have various effects on the local ecosystem. Introduced species that become established and spread beyond the place of introduction are considered "naturalized". The process of human-caused introduction is distinguished from biological colonization, in which species spread to new areas through "natural" (non-human) means such as storms and rafting.
The impact of introduced species is highly variable. Some have a negative effect on a local ecosystem, while other introduced species may have no negative effect or only minor impact. Some species have been introduced intentionally to combat pests. They are called biocontrols and may be regarded as beneficial as an alternative to pesticides in agriculture for example. In some instances the potential for being beneficial or detrimental in the long run remains unknown. The effects of introduced species on natural environments have gained much scrutiny from scientists, governments, farmers, and others.
Species that were intentionally or unintentionally brought by humans into a new geographic area or environment which is outside of their native range. Contrast indigenous species.