Monday 16 September 2013

An invasive American Paper Wasp in northern Spain.

Invasive species - species which have been introduced to parts of the world to which they are not native by human activity - can present a major challenge to native species and ecosystems, often quickly replacing similar native species due to a lack of specific parasites or predators, and frequently going on to reach epidemic population levels, significantly altering local ecosystems. 

In a paper published in the journal Zootaxa on 19 June 2012, Leopoldo Castro of Teruel Aragon, eastern Spain, Andrés Arias of the Departmento Biología de Organismos y Sistemas at the Universidad de Oviedo, and Antonio Torralba-Burrial of the Cluster de Energía, Medioambiente y Cambio Climático at the Universidad de Oviedo, recored the presence of breeding colonies of the American Paper Wasp Polistes major at Oviedo in northern Spain.

Nest of Polistes major at Oviedo, photographed in 2008, showing several females and eggs. Castro et al. (2013).

Polistes major is larger than any European member of the genus Polistes, and has a distinctive yellow and brown pattern, distinct from the black and yellow pattern of European members of the genus, and most other large European Wasps and Bees. Like the European Wasps it is a weekly social species with groups of females building small colonies under eaves, bridges or culverts or hanging from branches or metal beams, but with each female producing and tending her own eggs and young. All members of the genus Polistes feed on the Caterpillars of Butterflies and Moths, but the larger American species potentially takes more, and larger, prey.

The European Paper Wasp Polistes dominulus, near el Perelló, Catalonia, Spain, in April 2008. Hans Hillewaert/Wikimedia Commons.

Castro et al. speculate that the Wasp could have been introduced to Spain via imported goods from North or Central America, such as timber or fruit, which are regularly imported from the New World via ports in northern Spain. The species was witnessed breeding repeatedly over the period 2008-2012, suggesting that it has indeed become naturalized in the area. Polistes major is naturally found from the southern United States to southern Peru and northern Brazil, including much of the Caribbean. The European Paper Wasp Polistes dominulus has been introduced to several areas within this range, and appears to have effectively outcompeted the American Wasp.  However this may be due to an absence of predators or pathogens that can tackle the European Wasp in the Americas, and the reverse may happen in Europe. Instances of two species each replacing the other in their native habitat have been recorded in the past.

Though larger than the European Paper Wasp, the American Wasp is not notably more aggressive, however when it does sting it delivers significantly more venom. This is not usually life threatening unless the victim is allergic to the venom, but when an allergic reaction does occur this needs to be treated with a specific anti-venom, which is not currently available in Spanish hospitals, presenting a small, but significant, threat to public health.

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