Wednesday, January 24, 2007

YELLOW CRAZY ANTS ON CHRISTMAS ISLAND

Yellow crazy ant (Anoplolepsis gracilipes) is one of the largest and most destructive invasive ants (1). The native range of the species is not known exactly (2), “it may have been originated from Asia or Africa” (1). Yellow crazy ant invaded places such as Africa (South Africa), Asia (Malaysia) South America (Brazil) and Pacific Ocean (Hawaii). Anoplolepsis gracilipes was accidentally introduced to Christmas Island 1915 (3 ) and 1934 (3 ) and widespread to the entire island (3 ) .

Yellow crazy ant has unusually long leg and antennae. The researchers detected one super colony of Anoplolepsis gracilipes in 1989 on a high terrace above the Grotto (3 ) . The super colonies were again detected by researchers from Melbourne’ Monash University in 1997. The researchers were investigating the role of red land crab (Geocarcoidea natalis) on the Christmas Island ecosystem (4).

The Yellow crazy ant killed and displaced approximately ten(3) to twenty (3) millions of crabs on the rainforest floor. Crabs are keystone species of the rainforest. Anoplolepsis gracilipes consumed indigenous crabs and also occupied their burrows. They use formic acid to defend and to suppress their prey such as coconut crabs and reptiles (3 ).

The absences of crabs lead to the growth of seedling and spread of weeds on the Christmas Island. The population of Dendrocnide peltata began to increase and closed tracks which were used by people during their visitation on the Island (3) . At about ninety percent of the trees and shrubs were swarmed with sooty mould which resulted to the extensive canopy dieback. The population of indigenous birds, reptiles and mammals were also reduced. Studies indicated that the predation of immature Fregata andrewsi by crazy ant will result to decline of its population by eighty percent in the next thirty years (5). Anoplolepsis gracilipes is a dangerous agricultural pest (2).

The Park staff and experts struggled to find an appropriate method of baiting ants in 1999 and 2000. The amount of $1.5 from Natural Heritage trust was used to control crazy ants in 2000-2001(5). The successful eradication campaign took place in September 2002 and aerial baiting was used followed by continuous monitoring (5).

References

1. O’Dowd. 2006. Anoplolepis gracilipes (insect) [Online]. [cited 2007 Jan 24] Available from:
http://www.issg.org/database/species/ecology.asp?si=110&fr=1

2. Wikepedia Contributors. Crazy ant [Online] Wikepedia,The free Encyclopedia; 2007 Jan 12; 03:23 UTC [ cited 2007 January 24]. Available from: http://en.wikipedia.org/wiki/Yellow_crazy_ant

3. DEH. Yellow crazy. [Online]. [cited 2007 Jan 24] Available from: http://www.deh.gov.au/parks/christmas/fauna/crazy.htm

4. Kingsley D. 2003. Crazy ant lose battle, but still at war. [Online]. [cited 2007 Jan 24]
http://www.abc.net.au/science/news/stories/s796955.htm

5. Sue Matthews. 2004. Tropical Asia invaded: The growing danger of invasive alien species Global Invasive Species Programme [Online]. [cited 2007 Jan 24] Available from:

Gorse (Ulex europaeus) in Australia

Gorse (Ulex europaeus) is considered as one of the worst weeds in Australia. It is regarded as one of the 100 destructive invasive species (1) . Gorse has both economic and environmental impact. The weed is mostly invaded Tasmania and Part of Victoria (2 ).

Gorse is an indigenous species to Europe from Scotland south to Portugal, Galiza and East of Belgium. (1). Gorse is introduced to “Panama, Argentina, South Africa, China, Indonesia, United States, Hawaii, Canada, Indonesia, New Zealand, Mauritius, Ecuador, Tanzania, Uruguary, Sri Lanka, Turkey and Australia” (2 ). Gorse were introduced to agriculture as a hedge and for ornamental purposes (2)

Gorse is a perennial evergreen shrub. The young braches of the gorse are typically spine. Gorse grows in area that receives 650-900mm (3) during the year. However, the gorse also adapted to grow in Tasmania West Coast where the mean rainfall is 2400mm (3). It is also known to grow well on fertile soil, heavy clays, disturbed and light soil. The gorse can survive on poor soil nutrient because they are able to fix Nitrogen. The gorse is restricted to higher rainfall areas and is mainly found in the Fleurieu Peninsula (3).

The species displaces indigenous plants. The gorse has both the negative and positive impacts. Gorse changes a soil condition by both acidifying soil and fixing nitrogen. The gorse removes and preserves nutrients for example Sodium, Calcium and Magnesium and it weakens the soil. The bare soil is mostly found between individual gorse and results to soil erosion especially at the steep slopes. Goose decreases the quantity of forage when they are introduced on rangeland. Gorse is also blamed to disturb the growth of conifer trees. The foliage and seeds of the gorse are highly flammable. The fire which is produced by gorse is hotter comparing to the fire produced by other weeds (2) .The gorse also has positive impacts. It is usually used as a hedge plant, windbreaks, ornamental shrubs, gully reclamation, medically purposes and food for livestock (3).

The thickets of gorse can be burnt to the same level with the ground. The seedling will then spray in the next year to decrease seedlings (3). The spray will follow to kill the regrowth of the species. The gorse can be controlled by using mechanical clearing which can control large infestation. The tractor or bulldozers with rippers can be used (3).

References

1. Wikepedia Contributors. Common Gorse [Online] Wikepedia,The free Encyclopedia; 2007 Jan 21; 15:30 UTC [ cited 2007 January 24]. Available from: http://en.wikipedia.org/wiki/Common_Gorse

2. Hill R. 2005. europaeus (shrub,tree). [Online]. [cited 2007 Jan 24] Available from:

http://www.issg.org/database/species/ecology.asp?fr=1&si=69&sts=

3. CRC. 2003. Gorse (Ulex europaeus) [Online]. [cited 2007 Jan 24] Available from:

http://www.deh.gov.au/biodiversity/invasive/publications/pubs/u-europaeus.pdf