The small Indian mongoose (Herpestes auropunctatus) has a slender body with short legs. The head is elongated with a pointed muzzle. The tail is robustly muscular at the base and tapers gradually throughout its length, ending in tufts of slightly longer fur that are prized by paint brush manufacturers (Bailo and Sustic, 2012). Length of head and body is 509 to 671mm. Ears are short and rounded (15-30mm -- Roy, 2001) and project only slightly beyond the fur. Feet have five toes with long sharp non-retractile claws. Hair is short. Both sexes have an extensible anal pad with ducted glands lateral to the anus. Fur is soft, pale to dark brown flecked with golden spots. Underside is paler than rest of body. Eyes are amber/brown but are blue green in young animals. There is distinct sexual dimorphism. Females range in length from 509 to 578mm with a mean of 540mm. Sexual dimorphism is even more pronounced in populations that have been introduced to island ecosystems for over a century or more (Simberloff et al. 2000). Body mass at sexual maturity ranges from 305 to exceptionally just over 1 kg in large adult males with a mean of 434g. Males have a wider head and more robust body ranging in length from 544 to 671mm with a mean of 591mm (Nellis et al. 1989).
The shell of G. kibweziensis is translucent white, and dorso-ventrally distorted due to allometric changes during shell ontogeny. The juvenile shell is discoidal dome-shaped;the adult shell more globose and with the axis of coiling at about 13° angle to the axis of the juvenile. When the adult shell is examined in apertural view, the juvenile whorls sit atop and displaced to one side by the broader last two whorls of the adult whorls. Adult whorls with broadly rounded periphery. Aperture rounded, without barriers, with somewhat thickened and slightly reflected margins;parietal callus well developed. Umbilicus a minute perforation.The protoconch is smooth. The teleconch whorls are delicately ribbed.
G. kibweziensis is a non-specific predatory snail, taking a number of other snail species as prey. The species is not widely recognized as invasive. While it has become widely distributed in the islands of the Pacific and Indian Oceans as a biological control agent against giant African snails, continues to be spread in at least some regions by human agencies, and is known to interact with some native mollusc species, G. kibweziensis has not been unequivocally confirmed as threatening ecosystems, habitats or species or having major economic consequence.
Predation on native snails in regions to which G. kibweziensis has been introduced is undoubtedly occurring. Concern about G. kibweziensis effects on native land snail communities has been expressed in a number of countries to which the species has been introduced as a biological control agent, but definitive evidence for such effects is presently lacking. The use of generalized predators in biological control programs has long been recognized as unsafe due to expected environmental impacts, not least adverse effects on non-target species.
P. hysterophorus is an erect, much-branched with vigorous growth habit, aromatic, annual (or a short-lived perennial), herbaceous plant with a deep taproot. The species reproduces by seed. In its neotropical range it grows to 30-90 cm in height (Lorenzi, 1982, Kissmann and Groth, 1992), but up to 1.5 m, or even 2.5 m, in exotic situations (Haseler, 1976, Navie et al., 1996). Shortly after germination the young plant forms a basal rosette of pale green, pubescent, strongly dissected, deeply lobed leaves, 8-20 cm in length and 4-8 cm in width. The rosette stage may persist for considerable periods during unfavourable conditions (such as water or cold stress). As the stem elongates, smaller, narrower and less dissected leaves are produced alternately on the pubescent, rigid, angular, longitudinally-grooved stem, which becomes woody with age. Both leaves and stems are covered with short, soft trichomes, of which four types have been recognized and are considered to be of taxonomic importance within the genus (Kohli and Rani, 1994).;Flower heads are both terminal and axillary, pedunculate and slightly hairy, being composed of many florets formed into small white capitula, 3-5 mm in diameter. Each head consists of five fertile ray florets (sometimes six, seven or eight) and about 40 male disc florets. The first capitulum forms in the terminal leaf axil, with subsequent capitula occurring progressively down the stem on lateral branches arising from the axils of the lower leaves. Thousands of inflorescences, forming in branched clusters, may be produced at the apex of the plant during the season. Seeds (achenes) are black, flattened, about 2 mm long, each with two thin, straw-coloured, spathulate appendages (sterile florets) at the apex which act as air sacs and aid dispersal.
P. hysterophorus is known to reduce the yield of various crops and to compete with pasture species in various countries. However, the yield loss and specific effects on the crops have not been quantified in all countries (Rubaba et al., 2017).;In Australia, the main impact of P. hysterophorus has been in the pastoral region of Queensland, where it replaces forage plants, thereby reducing the carrying capacity for grazing animals (Haseler, 1976, Chippendale and Panetta, 1994). Serious encroachment and replacement of pasture grasses has also been reported in India (Jayachandra, 1971) and in Ethiopia (Tamado, 2001, Taye, 2002). The weed is also able to invade natural ecosystems, and has caused total habitat changes in native Australian grasslands and open woodlands (McFadyen, 1992).;In India, the yield losses are reported as up to 40% in several crops and a 90% reduction of forage production (Gnanavel, 2013). P. hysterophorus is now being reported from India as a serious problem in cotton, groundnuts, potatoes and sorghum, as well as in more traditional crops such as okra (Abelmoschus esculentus), brinjal (Solanum melongena), chickpea and sesame (Kohli and Rani, 1994), and is also proving to be problematic in a range of orchard crops, including vineyards, olives, cashew, coconut, guava, mango and papaya (Tripathi et al., 1991, Mahadevappa, 1997, Gnanavel, 2013).;Similar infestations of sugarcane and sunflower plantations have recently been noted in Australia (Parsons and Cuthbertson, 1992, Navie et al., 1996), whilst in Brazil and Kenya, the principal crop affected is coffee (Njoroge, 1989, Kissmann and Groth, 1992). In Ethiopia, parthenium weed was observed to grow in maize, sorghum, cotton, finger millet (Eleusine coracana), haricot bean (Phaseolus vulgaris), tef (Eragrostis tef), vegetables (potato, tomato, onion, carrot) and fruit orchards (citrus, mango, papaya and banana) (Taye, 2002). In Pakistan, the weed has been reported from number of crops, including wheat, rice, sugarcane, sorghum, maize, squash, gourd and water melon (Shabbir 2006, Shabbir et al. 2011, Anwar et al. 2012).;In Mexico, the species is reported as a weed in cotton, rice, sugarcane, Citrus spp, beans, safflower, sunflower, lentils, corn, mango, okra, bananas, tomato, grapes, alfalfa, chili peppers, luffa, marigolds and other vegetables and fruit orchards. It is also a weed in nurseries. In Argentina is reported as a weed of tobacco fields (CONABIO, 2018).;Gnanavel (2013) also reports the following detrimental effects of P. hysterophorus on crops: it inhibits nitrogen fixing bacteria in legumes, the vast quantity of pollen it produces (ca. 624 million/plants) inhibits fruit setting, it is an alternative host for viruses that cause diseases in crop plants, and it is an alternative host for mealy bugs.
L. peploides is an emergent and floating herbaceous perennial macrophyte. It has glabrous or pubescent stems 1-30 dm that can creep horizontally as well as grow vertically. Early growth resembles a rosette of rounded leaves growing on the water’s surface. Alternate leaves are polymorphic and less than 10 cm long and oblong to round, often lanceolate at flowering. The species exhibits root dimorphism and has adventitious roots that form at nodes and ensure oxygen uptake. Flowers are 5-merous (pentamerous), grow from leaf axils, are bright yellow, and can be from 7 to 24 mm long. Fruit is in a five-angled reflexed capsule, about 3 cm long that contains 40-50 seeds 1.0-1.5 mm long, embedded in the inner fruit wall (EPPO, 2004;The Jepson Online Interchange, 2009).
L. peploides is a productive emergent aquatic perennial native to South and Central America, parts of the USA, and likely Australia (USDA-ARS, 1997). It was introduced in France in 1830 and has become one of the most damaging invasive plants in that country (Dandelot et al., 2008). It is often sold as an ornamental, which likely explains its introduction to Europe. It has been more recently introduced to areas beyond its native range in the USA, where it is often considered a noxious weed (INVADERS, 2009;Peconic Estuary Program, 2009). L. peploides is adaptable, and tolerates a wide variety of habitats where it can transform ecosystems both physically and chemically. It sometimes grows in nearly impenetrable mats;it can displace native flora and interfere with flood control and drainage systems, clog waterways and impact navigation and recreation (Peconic Estuary Program, 2009). The plant also has allelopathic activity that can lead to dissolved oxygen crashes, the accumulation of sulphide and phosphate, ‘dystrophic crises’ and intoxicated ecosystems (Dandelot et al., 2005).
Impacts on the local environment by L. peploides can be devastating. The species possesses an allelopathic activity that has year-long effects on water quality and can lead to impoverished flora by decreasing seedling survival of vulnerable native taxa (Dandelot et al., 2008). L. peploides can also cause severe hypoxia and sometimes anoxia during the summer. It can also lead to reduced sulphate and nitrate levels and increased sulphide and phosphate concentrations. These combined effects have the capability of fomenting what Dandelot et al. (2005) refer to as “a dystrophic crisis” and an intoxicated ecosystem. The plant has been reported to outcompete native Myriophyllum and Potamogeton species in France, which translates to a reduction in macroinvertebrate habitat (Dutartre, 1986;CEH, 2007). It also supplants native wetland grasses, some of which are used as forage for livestock (CEH, 2007).
N. reynaudiana is a short-rhizomatous perennial woody grass, typically 2-3 m, but sometimes taller. Culms erect, 3-10 mm diameter, with solid culm internodes. Leaf blades flat, 20-100 cm long, 8-25 mm wide. Leaf-blade surface smooth. Leaf sheaths glabrous. Ligule pilose, 1-2 mm. Inflorescence a dense, open panicle, 30-50 cm long, branches slender and nodding. Spikelets 6-9 mm, with 4-10 florets. The lower floret sterile, resembling glume and lacking a palea. Glumes subequal, 2-3 mm, acute, glabrous. Lemmas 4 mm, purplish, lateral veins conspicuously ciliate with 2 mm hairs and lemma with 1-2 mm recurved awn. Tucker (1990) noted that the species was unusual in having an abaxial (external) ligule, a cartilaginous ridge that is pilose when young.
The large stature of N. reynaudiana makes detection straightforward. Inspectors in its naturalized range should, however, be able to distinguish it from several other large grasses, including Phragmites species, Pennisetum purpureum and Arundo donax.
N. reynaudiana is a tall woody grass that has become naturalized outside of its natural range in the USA (southern Florida) and in the Bahamas on limestone-dominated substrates. In Florida, N. reynaudiana became established following planting experiments in Miami-Dade County in 1916 (Gordon, 1998). It has become widely established in at least a six-county region of the southern peninsula. The species is an aggressive invader of pine rockland habitats, but also can colonize rockland hammocks and beach dunes. N. reynaudiana is also an abundant weed of roadsides and other disturbed uplands in southern Florida. In pine rockland ecosystems the species forms dense, nearly monospecific stands, outcompeting native species. It alters fire behaviour, increases organic litter accumulation and alters succession patterns. It is known to displace a large number of endangered and rare species. N. reynaudiana was found in the Bahamas in 1974 and has since spread to at least three islands;Abaco, Andros and Bimini. In the Bahamas, N. reynaudiana is found in dry to moist disturbed areas and is a potential threat to pine rockland, coppice and coastal habitats. Eradication of N. reynaudiana is both labour-intensive and costly.
N. reynaudiana is reported to be a weed of upland rice in Thailand (Moody 1989;Galinato et al., 1999). Crane et al. (2001) lists N. reynaudiana as a common weed found in orchards in Miami-Dade County, Florida.
The following description is adapted from Austin and Staples (1991) and Acevedo-Rodríguez (2005)
Turbina corymbosa is a perennial, neotropical vine that has been introduced as an ornamental in the Canary Islands, Australia and several Old World countries. It is a serious problem in northern Queensland, Australia, where it is invading rainforest ecosystems and displacing native vines and shrubs, and is sometimes considered an environmental and agricultural weed elsewhere.
It is reported as a weed of bean (Phaseolus vulgaris) and orange (Citrus sinensis) crops in Cuba (Sampedro Romero et al., 2002;Castellón-Estévez et al., 2011).
V. rigida grows as an herbaceous perennial plant 50-60 cm in height (ISSG, 2015). It can form dense stands via rhizomes and stolons (Munir, 2002). Leaves are arranged opposite to subopposite along the square stems and leaves clasp the stem (Tveten and Tveten, 2010;ISSG, 2015). The stiff, dark green leaves are oblong in shape, 5-10 cm long, with pointed tips and coarsely serrated edges (ISSG, 2015). Leaves and stems are covered in rough hairs (Tveten and Tveten, 2010). Cylindrical spikes of flowers forming spreading clusters are held at the ends of stems. Each flower calyx is 3-3.5 mm long and the corolla-tube is 5-10(-12) mm long (ISSG, 2015). Flowers are purple in colour and fragrant. Dry fruits separate into four, one-seeded parts. Each seed is about 2 mm long (ISSG, 2015).
V. rigida is an herbaceous perennial planted as a fast spreading groundcover (Royal Horticultural Society, 2015) and is listed as weedy in many countries (Randall, 2012). It is principally found in disturbed areas but can spread into grasslands and forests and is a weed of cotton fields (ISSG, 2015). However, there is little information on the species impact in agricultural or natural ecosystems. It spreads via rhizomes and seeds (ISSG, 2015), but the extent of dispersal by seed and whether the plant has a seedbank is unknown.
V. rigida is a weed in pastures and cotton fields (Munir, 2002) and turf grass (Georgia Turf, 2015) but appears to be a relatively minor weed. Where a weed of cotton fields in Australia (Johnson and Hazlewood, 2002) no information was available on the magnitude of effect or what crop stage is affected. It is considered a weed in cultivation of bald cypress in Florida (Osiecka and Minogue, 2012).
U. gibba is an annual or perennial submerged or free-floating aquatic plant. Rhizoids absent or present, filiform, branched. Stolons filiform, much branched, often mat-forming. Traps lateral on leaf segments, stalked, ovoid, 1-2.5 mm, mouth lateral;appendages 2, dorsal, branched, setiform, with shorter setae. Leaves numerous on stolons, 0.5-1.5 cm;primary segments (1 or) 2, unbranched or sparsely dichotomously branched into 3-8 ultimate segments;ultimate segments capillary, slightly flattened, margin entire or sparsely denticulate, apex and teeth setulose. Inflorescences erect, 2-15 cm, 1-3(-6)-flowered;peduncle terete, 0.3-0.5 mm thick, glabrous;scale 1, similar to bracts;bracts basifixed, semiorbicular, ca. 1 mm, minutely glandular, apex truncate and obscurely dentate. Pedicel erect to spreading, 2-12 mm, filiform;bracteoles absent. Calyx lobes subequal, broadly ovate to orbicular, 1.5-2 mm, apex rounded. Corolla yellow, 4-8 mm;lower lip slightly smaller than upper lip, base with a prominent 2-lobed swelling, apex rounded;spur narrowly conic to cylindric from a conic base, shorter or longer than corolla lower lip, distal part sparsely stipitate glandular, apex obtuse;palate densely pubescent;upper lip broadly ovate to suborbicular, ca. 2 × as long as upper calyx lobe, apex obscurely 3-lobed. Filaments 1-1.5 mm, curved;anther thecae confluent. Ovary globose;style evident;stigma lower lip transversely elliptic, upper lip obsolete. Capsule globose, 2-3 mm in diam., 2-valvate. Seeds lenticular, 0.8-1 mm in diam., margin broadly winged, wing shallowly and irregularly dentate;seed coat with small prominent reticulations (Zhenyu and Cheek, 2011).
An interactive key for invasive plants in New Zealand has been developed by Dawson et al. (2010).
U. gibba is an annual or perennial submerged or free-floating carnivorous aquatic plant. It has been identified as such a specialist invasive species and may outcompete native bladderworts in lowland wetland ecosystems in countries where it is introduced. It was intentionally introduced, as an aquarium plant, to New Zealand in 1980, where it is now fully naturalized.
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 description is adapted from Flora of North America Editorial Committee (2015).
A. semibaccata is a low-growing shrub native to Australia. It is valued as a fodder plant and, along with many other Atriplex species, has been introduced around the world as a drought and salt tolerant forage. It was introduced to the USA where it has escaped cultivation and is now invasive in coastal grasslands, scrub and saline area, where it can form a dense cover inhibiting the growth of native plants. The California Invasive Plant Council classifies its potential impact on native ecosystems as moderate and control and eradication of this species appears possible. Many other Atriplex species are beginning to be reported as somewhat invasive in other parts of the world and the genus merits further attention in this regard.
H. coccineum is a vigorous perennial herb. Pseudostems grow up to 1.5-2 m height. Leaves sessile;ligule 1.2-2.5 cm;leaf blade narrowly linear, 25-50 × 3-5 cm, glabrous, base subrounded or attenuate, apex caudate-acuminate. Spikes cylindric, usually dense, glabrous or sparsely villous;bracts oblong, 3-3.5 cm, leathery, sparsely pubescent, rarely glabrous, 3-flowered, margin involute or rather flat, apex obtuse or acute. Flowers red. Calyx ca. 2.5 cm, sparsely pubescent especially at 3-toothed apex. Corolla tube slightly longer than calyx;lobes reflexed, linear, ca. 3 cm. Lateral staminodes lanceolate, ca. 2.3 cm. Labellum orbicular, ca. 2 cm wide or rather small, apex deeply 2-cleft. Filament ca. 5 cm;anther 7-8 mm. Ovary sericeous, 2.5-3 mm. Capsule globose, approximately 2 cm in diameter. Seeds red. (Flora of China Editorial Committee 2012).
Hedychium coccineum is an adaptable, tall, herbaceous, and very variable ornamental plant native to Asia. It can colonise natural or semi-natural habitats, from riverine fringe and mountain grasslands to forest understorey. In its introduced range, it can become dominant or co-dominant in natural or semi-natural environments, competing with and displacing indigenous species (e.g. in La Réunion, Africa;Brazil;South Africa). Similarly to other Hedychium species (i.e., Hedychium gardnerianum and H. coronarium), it is widely traded as a garden ornamental around the world. H. coccineum is included in the Global Invasive Species Database (2014) and the Global Compendium of Weeds (Randall, 2012) and is a declared weed and invasive species in some countries. Its environmental adaptability, high commercial appeal and growing impact in countries where it has established suggest its prospective spread in delicate ecosystems cannot be underestimated.
Infestations of H. coccineum have been reported in plantations in South Africa as well as limited access to plantations caused by the plant (Henderson, 2001).
S. minima is a deep-green, free-floating, rootless, aquatic fern (ISSG, 2006). Stems can be up to 6 cm and leaves are from 1-1.5 cm long and almost round to elliptic. They are obtuse or notched at the apex and round to heart-shaped at the base. The upward surfaces of the fronds are covered with stiff hairs, with four separated branches. The under surface of the leaves are brown and pubescent with slender and unbranched hairs (Flora of North America Editorial Committee, 1993). The stiff hairs on the fronds serve to trap air, thus providing buoyancy (Dickinson and Miller, 1998). Obscure veins are areolate and do not quite reach to the leaf edges. Sporocarps occur in groups of four to eight, with up to 25 megasporangia (Flora of North America Editorial Committee, 1993).
S. minima is free-floating, which makes it easier to identify than most submerged aquatic vegetation. Volunteer monitors should be trained on the identity and habit of this potential invader.
S. minima is a very productive free-floating, non-rooted aquatic fern native to South and Central America. It was introduced outside its native range in southern Florida, USA in 1926 (USGS, 2005). The plant is degrading wetland ecosystems in several states of the USA (Tipping and Center, 2005). S. minima has an extremely high reproductive potential;the plants can rapidly colonize bodies of water, forming thick mats that displace native species, impact water quality, impede recreational activities, and clog waterways and irrigation channels (Rayachhetry et al., 2002). S. minima is also resistant to desiccation, allowing it to be transported long distances out of water (ISSG, 2006). The species can act as an annual, dying back when temperatures decrease and causing harmful nutrient pulses and dissolved oxygen crashes (Dickinson and Miller, 1998).
S. minima is a highly competitive species with a very high growth rate. Colonies of S. minima can grow very densely, such that they shade light from valuable native submerged aquatic plant species (USACE-ERDC, 2002). Dense colonies can thus decrease local biodiversity and degrade the habitat (ISSG, 2006). The plant is also highly competitive among other free-floating species. A competition study specifically showed that S. minima had negative effects on the change in cover of the species Azolla caroliniana and Spirodela punctata (Dickinson and Miller, 1998). In Louisiana, USA native Lemna species were completely replaced by S. minima (ISSG, 2005).
Perennial, woody vine, 10-20 m in length. Stems are cylindrical, up to 2.5 cm in diameter, striate, puberulous;cross section of the stem with the pith hollow and the xylem tissue with wide rays. Leaves are opposite;blades 15-26 × 13-30 cm, ovate or broadly ovate, chartaceous, the apex acute or acuminate, the base cordiform, the margins lobate-dentate, ciliate;upper surface is dark green, shiny, puberulous, with slightly prominent venation;lower surface is light green, dull, glabrous or puberulous, with prominent venation;petioles 6-12 cm long. Flowers are arranged in axillary cymes;pedicels robust, cylindrical, 4-6 cm long;bracts light green, ovate, approximately 4 cm long, covering the calyx and the corolla tube. The calyx is green with the form of a ring, 4-5 mm long;corolla lilac-blue or white, with 5 lobes, the tube 6-7 cm long, light yellow inside, narrow at the base, the limb 6-7 cm in diameter. Fruits are capsules, approximately 3 cm long, subglobose at the base, the upper half in the form of a beak, explosively dehiscent in two halves (Acevedo-Rodríguez, 2005).
T. grandiflora is a woody vine included in the Global Compendium of Weeds and it is listed as a very aggressive weed impacting tropical and subtropical ecosystems (Randall, 2012). This species has been repeatedly introduced as an ornamental plant in many countries around the world, but it has become a serious environmental problem when it has escaped from cultivated areas and rapidly colonized natural habitats (ISSG, 2012). The rapid colonization of new habitat by this vine is mainly due to its capability to reproduce sexually by seeds and vegetatively by cuttings, fragments of stems and roots (USDA-NRCS, 2012). Once established, T. grandiflora completely smothers native vegetation by killing host-trees, out-competing understory plants, and negatively affecting the germination and establishment of seedlings of native species (Starr et al., 2003). Currently, T. grandiflora is classified as a “noxious weed” in Australia (Queensland Department of Primary Industries and Fisheries, 2007), and as an invasive species in Central America, the West Indies, Africa, and numerous islands in the Pacific including Hawaii, Fiji, French Polynesia, Palau, and Samoa (see distribution table for details;Acevedo-Rodríguez and Strong, 2012;ISSG, 2012;PIER, 2012).
P. pilosa is an annual or rarely short-lived perennial, succulent, prostrate to erect herb to 30 cm tall;roots fibrous to slightly fleshy;leaves fleshy, opposite or alternate, to 20 mm long, 3 mm wide, terete to hemispheric, linear to oblong-lanceolate, with conspicuous axillary hairs 1-18 mm long;flowers subtended by involucre of dense wool and 6-9 bracts, flowers mostly 5-12 mm wide, petals 5, dark pink-purple, stamens 5-12 or more, red, stigmas 3-6 lobed;capsules ovoid, to 4.3 mm, seeds black to gray, sometimes purplish, orbiculate, 0.5-0.7 mm in diameter.
Portulaca pilosa is a fleshy-leaved annual or short-lived perennial with low, sprawling growth habit. It is a weed throughout its range. It is thought to have originated in South America but its native range is uncertain. It occurs from South America north to the Caribbean and the southern USA, and is also found growing on some Pacific islands, Australia and parts of Asia, and perhaps Africa. This self-compatible species has a short life cycle with the ability to produce mature seed in less than two months. A single plant can produce nearly 300,000 seeds annually. The species has a high drought tolerance, and throughout its range it is predominantly a weed of disturbed dry soils. It is often found in coastal ecosystems such as dunes and rocky shores. It competes with native herbs in these habitats, including some endangered species and narrow endemics.
Although P. pilosa has a broad global range, it is not generally considered a problematic agricultural weed, despite its preference for disturbed soils. In the USA it is described as a common weed of one or more crops in Louisiana, Alabama, Georgia, South Carolina, North Carolina and Puerto Rico (Invasive.org, 2015).
Webb et al., (1988) describes V. litoralis as a
Verbena litoralis is a short-lived herbaceous plant, native to many of the tropical areas of Central and South America. Although the species has spread to other countries from its native environment, and is sometimes regarded as an invasive threat (in Australia and some states of the USA), it often seems to be restricted to disturbed habitats like roadsides, stream banks, tracks and waste places. Information on its effects on other plant species is not well reported, nor is there any evidence to suggest it has any serious impacts on specific environments or ecosystems.
No mention found of any particular species affected by its presence.
Recent molecular analysis has shown that Acanthaster planci is in fact a species complex consisting of four distinct clades from the Red Sea, the Pacific, the Northern and the Southern Indian Ocean. Benzie (1999) had previously demonstrated the genetic differentiation between A. planci from the Pacific and the Indian Ocean, and this genetic grouping is reflected in the distribution of colour morphs: grey-green to red-brown in the Pacific Ocean, and blue to pale red in the Indian Ocean (Benzie, 1999). Colour combinations can vary from purplish-blue with red tipped spines to green with yellow-tipped spines (Moran, 1997). Those on the Great Barrier Reef are normally brown or reddish grey with red-tipped spines, while those in Thailand are a brilliant purple (Moran, 1997). Adult A. planci usually range in diameter from around 20 to 30cm (PERSGA/ GEF 2003) although specimens of up to 60cm (and even 80cm) in total diameter have been collected (Chesher, 1969;Moran, 1997). The juvenile starfish begins with 5 arms and develops into an adult with an astounding 16 to 20 arms, all heavily armed with poisonous spines 4 to 5cm in length, which can inflict painful wounds (Moran, 1997;Birk, 1979). Arm values vary between localities with a range of 14 to 18cm given for the Great Barrier Reef (Moran 1997). Starfish are usually concealed during daylight hours, hiding in crevices (Brikeland and Lucas, 1990;Chesher, 1969). Groups of starfish often move as huge masses of 20 to 200 individuals, presenting a terrifying "front" which destroys the reef as it moves through (Chesher, 1969). Signs of starfish presence are obvious;the coral skeleton is left behind as the result of starfish feeding and stands out sharply as patches of pure white, which eventually become overgrown with algae (Chesher, 1969). In some cases, herbivorous sea urchins move in to feed on algae, creating a pattern against the white coral that resembles the holes of swiss cheese (Tsuda et al. 1970).
Coral gardens from Micronesia and Polynesia provide valuable marine resources for local communities and environments for native marine species such as marine fish. In coral ecosystems already affected by coral bleaching, excess tourism and natural events such as storms and El Nino, the effects of the invasive crown-of-thorns starfish (Acanthaster planci) on native coral communities contributes to an already dire state of affairs. Acanthaster planci significantly threatens the viability of these fragile coral ecosystems, and damage to coral gardens by the starfish has been quite extensive in some reef systems. Outbreaks in the Pacific appear to be more massive and widespread than those elsewhere. This may reflect different patterns of outbreak between Pacific and Indian Ocean populations, which have recently been shown to form separate clades of an A. planci species complex. (Vogler et al. 2008;and see 'Description' section).
A. grandifolium is a perennial herb or shrub that grows up to 3 m tall. Its branches are covered with long and slender hairs. The leaves are simple and alternate and are borne by a 5-20 cm long petiole. Awl-shaped, caducous stipules are found at the base of the petiole. The leaf’s blade is ovate, up to 20 by 15 cm, its base is cordate and its apex acute or subacuminate. Leaves have a toothed margin, 6-7-nerved. Both surfaces of the leaf are covered with stellate hairs. Inflorescences bearing one or two flowers are located in the leaf axils. The peduncles (main stalk of the inflorescence) are shorter than the petioles (4 to 5 cm long and up to 12 cm in mature fruits). Flowers are bisexual and lack the epicalyx. They have five yellow petals, which are united at the base of the staminal colum and enclosed by a 5-lobed calyx, 1 to 1.5 cm long. The staminal column is very short (5-8 mm long) with many stamens. The style branches are yellow, stigmas maroon and the ovary superior. The fruit is subglobose and splits into single-seeded parts when dry. Each fruit contains two to five blackish, kidney-shaped and sparsely pubescent seeds.
Native to South America, A. grandifolium is widely cultivated as a fibre plant and ornamental in the tropics where it has become naturalized. This garden escape is a relatively common weed of waste areas, disturbed sites, roadsides and drains, but is also an occasional weed of disturbed and undisturbed natural ecosystems (e.g. tall shrublands, grasslands and riparian areas). Given this species’ prolific seed production A. grandifolium has become a problematic weed in some of the regions where it occurs. There is little information available on the impacts of this species. However in Hawaii, along with other invasive species, it is reported as having a detrimental effect on Spermolepis hawaiiensis and Scaevola coriacea, two endangered and threatened species.
In spite of the reported damage caused by its congenic species A. theophrasti, there is no indication that A. grandifolium can reduce crop yields or increase costs (CGAPS, 2014)
E. lehmanniana is a perennial grass, without rhizomes but sometimes with stolons;culms up to 90 cm tall, erect, ascending or decumbent and rooting at the nodes, branched, glabrous at the nodes (but the internodes glabrous or pilose), eglandular;basal leaf sheaths shortly pilose below or sometimes glabrous, chartaceous, ± compressed and keeled, eglandular, persistent;ligule a line of hairs;leaf laminas 6-25 cm x 1.5-3.5 mm, linear to broadly linear, flat to involute, puberulous above, eglandular. Panicle (7-)9-16(-18) cm long, ovate to narrowly ovate-elliptic, loose and open, the spikelets condensed about the branchlets on pedicels 0.5-1 mm long, the primary branches not in whorls, terminating in a fertile spikelet, glabrous in the axils, eglandular. Spikelets 4-11(-12) x 1-1.5 mm, oblong to linear, lightly laterally compressed, (4-)7-15-flowered, the lemmas disarticulating from below upwards, the rachilla persistent below, sometimes becoming fragile above;glumes 1.3-2.0 mm long, subequal, 1-veined, reaching to between half and two-thirds (even three-quarters) of the way along the adjacent lemmas, lightly keeled, narrowly oblong-lanceolate in profile, smooth or scaberulous on the keel, subacute at the apex;lemmas 1.8-2 mm long, 3-veined, lightly keeled, elliptic-oblong in profile, membranous with distinct lateral nerves, appressed to the rachilla, those in opposite rows scarcely overlapping, the rachilla ± visible between them, dark green, grey-green or reddish, faintly asperulous on the back, obtuse to acute, shallowly 3-lobed at the apex;palea persistent or rarely deciduous with the lemma, glabrous on the flanks, the keels slender, wingless, smooth or scaberulous;stamens 3, anthers 0.7-1 mm long. Caryopsis 0.6-0.8 mm long, oblong to elliptic (PROTA, 2015).
Eragrostis lehmanniana is a grass native to southern Africa and introduced to arid areas of India, the USA, Brazil, Argentina and Venezuela. It has become invasive, especially in the southwestern USA (primarily in Arizona), where it was introduced in the 1930s for range restoration purposes. E. lehmanniana is also used as a forage grass, despite only the immature plants being palatable. It reproduces primarily by seeds, which are easily spread by wind, water, animals and vehicles. E. lehmanniana impacts ecosystems by altering fire regimes and displacing indigenous species.
Densely caespitose perennial without rhizomes or stolons;culms up to 90 (100) cm tall, strongly compressed below, erect, unbranched, glabrous at the nodes, eglandular;basal leaf sheaths glabrous, chartaceous, strongly compressed, keeled and usually flabellate, eglandular, persistent;ligule a line of hairs;leaf laminas 10-80 cm x 1.5-4 mm, linear, flat or folded, glabrous, eglandular or with punctate glands along the midnerve. Panicle 10-35 cm long, narrowly oblong to narrowly ovate, the branches ascending or spreading, the spikelets appressed to the branchlets on pedicels 1.5-2 mm long, the primary branches not in whorls (but sometimes loosely clustered), terminating in a fertile spikelet, glabrous or thinly pilose in the axils, eglandular. Spikelets 6-13.5 x 0.5-2 mm, linear to narrowly oblong, laterally compressed, 9-13-flowered, the lemmas disarticulating from below upwards, the rhachilla persistent;glumes unequal, keeled, oblong-lanceolate in profile, scaberulous on the keel, acute at the apex, the inferior 0.5-0.8 mm long, reaching to about 1/3 the way along the adjacent lemma, the superior 0.9-1.5 mm long, shorter than the adjacent rhachilla internode or just exceeding the base of the adjacent lemma;lemmas 1.8-2.5 mm long, keeled, semi-ovate in profile (with straight or rarely concave keel and gibbous margins), membranous with prominent lateral nerves, appressed to the rhachilla, those in opposite rows not overlapping, the rhachilla visible between them, olive-green, glabrous but with punctate glands on the nerves, subacute at the apex;palea persistent, glabrous on the flanks, the keels slender, wingless and glabrous to scaberulous or slightly thickened with punctate glands;3 anthers, (0.9)1.6-2 mm long. Caryopsis (0.8)0.9-1.2 mm long, oblong to elliptic (Cope, 1999).
Eragrostis plana is a perennial grass native to southern African savannas. It is invasive in grassland ecosystems in southern Brazil, Uruguay and Argentina. In Rio Grande do Sul, Brazil, where it was accidentally introduced as a seed contaminant in the 1950s, it was then planted across the area as a forage alternative, but has since outcompeted native species in pastures and in native grasslands. The species is currently established on more than two million hectares of grasslands in southern Brazil. There, it flowers every three weeks in the warm months, tolerates frost and resprouts if mowed or grazed. E. plana thrives over compacted soil, being common on roadsides and parking lots, as well as in overgrazed areas. Seeds remain viable in the soil more than 24 years. It has proven a poor forage species and its invasion has resulted in economic losses to cattle ranchers.
A. capillaris is a low-growing, rhizomatous, perennial grass. It forms dense swards of quite fine leaves that taper almost directly from the ligule down to the finely pointed tip. The flowering panicle is finely branched with numerous very small spikelets forming a reddish-purple haze over the mat of leaves. Culms are tufted, geniculate or decumbent and rooting at base, 20-70 (occasionally 100) cm tall. Leaf sheaths are smooth with linear blades, flat or inrolled, 2-15 cm x 1-4 mm, scabrous or nearly smooth with acuminate apex. The ligule on non-flowering shoots is 1-2 mm, shorter than wide and truncate. The panicle is elliptic in outline, up to 20 cm long, open and very lax with 2-5 spreading branches per node. Branches of the panicle are capillary, 1.5-3.5 cm, with purplish brown spikelets (1.5-2.5mm). Glumes are elliptic-lanceolate, subequal or lower glume slightly longer, lower glume scabrid along keel, the upper glume often smooth with acute apex. The entire plant is hairless. Seeds are small and brown;roots have scaly rhizomes and occasionally stolons (Edgar and Forde, 1991;Zheng et al., 2006;Quattrocchi, 2006;Gateley, 2015;Flora of China Editorial Committee, 2016;Garry Oak Ecosystems Recovery Team, 2016;New Zealand Plant Conservation Network, 2016).
Common bent, Agrostis capillaris, is a typical and often abundant species in grasslands on acidic or neutral soils. It is native and widespread throughout most parts of Europe, western and southwestern Asia and North Africa. Within its native range the species is often abundant in nutrient poor pastures, along roadsides or on disturbed ground. A. capillaris has been intentionally introduced as a pasture grass and as a turf grass for lawns, in particular for golf courses, into a number of countries and has become widespread in North America, Australia, New Zealand and parts of South America. It has been recorded as invading native grasslands in part of its exotic range, including prairies in North America.
A. capillaris has not been reported as a weed in specific cropping situations, but can invade pastures and other grasslands.
Perennial, fast-growing, woody vine that climbs using tendrils at the end of the inflorescence axes and attains 5-13 m in length. Stems are puberulent, pentagonal, with many lateral branches. Leaves are alternate, ovate, triangular-ovate, or almost lanceolate, chartaceous, 5-14.5 × 2-7 cm, the apex is acute or acuminate, the base is cordiform or truncate, and the margins are crenulate, sometimes ciliate. The upper surface of leaves is light green slightly shiny, puberulent, with the venation sunken;lower surface pale green, dull, puberulent or glabrous, with prominent venation;petioles are 1-5 cm long, reddish, puberulent, cylindrical or subwinged. Flowers are bisexual, in axillary racemes or terminal panicles, 10-20 cm long, terminating in a pair of spiral tendrils;pedicels 3-4(-10) mm long. The perianth is about 4-7 mm long, of 5 ovate or elliptical tepals, intense pink or white;staminal column 2-3 mm long, of the same colour as the tepals. The fruit is a 3-angle-achene, 5-8 mm long (Acevedo-Rodríguez and Strong, 2005).
A. leptopus is a perennial vine, cultivated as an ornamental for its showy flowers, but which when neglected can grow quickly over other vegetation, spreading beyond its area of introduction. As an invasive vine, it is included in the Global Compendium of Weeds (Randall, 2012) and classified as one of the most aggressive weeds occurring in tropical and insular ecosystems (Langeland et al., 2008;Burke and DiTommaso, 2011;PIER, 2012).
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 ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the system through photosynthesis and is incorporated into plant tissue. By feeding on plants and on one another, animals play an important role in the movement of matter and energy through the system. They also influence the quantity of plant and microbial biomass present. By breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be readily used by plants and other microbes.
Ecosystems are controlled by external and internal factors. External factors such as climate, parent material which forms the soil and topography, control the overall structure of an ecosystem but are not themselves influenced by the ecosystem. Unlike external factors, internal factors are controlled, for example, decomposition, root competition, shading, disturbance, succession, and the types of species present.
Ecosystems are dynamic entities—they are subject to periodic disturbances and are in the process of recovering from some past disturbance. Ecosystems in similar environments that are located in different parts of the world can end up doing things very differently simply because they have different pools of species present. Internal factors not only control ecosystem processes but are also controlled by them and are often subject to feedback loops.
Resource inputs are generally controlled by external processes like climate and parent material. Resource availability within the ecosystem is controlled by internal factors like decomposition, root competition or shading. Although humans operate within ecosystems, their cumulative effects are large enough to influence external factors like climate.
Biodiversity affects ecosystem functioning, as do the processes of disturbance and succession. Ecosystems provide a variety of goods and services upon which people depend.
A functional system which includes the organisms of a natural community together with their environment.