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Revista Chilena de Historia Natural 85 (1): 147-154, 2012
Megastigmus aculeatus infestation on seeds of exotic roses invading wild communities of Andean Patagonia from Argentina
Megastigmus aculeatus Swederus (Hymenoptera: Chalcidoidea) infest Rosa species seeds both at the origin and invasion areas. The wasp larvae develop by consuming the entire seed. The M. aculeatus infestation was analyzed at different Rosa canina L. and Rosa rubiginosa L. populations and at isolated plants of Rosa multifl ora Thunb. At Norwestern Patagonian natural areas of Argentina. In R. rubiginosa, the most abundant species, we studied the wasp infestation prevalence and success and the possible infestation effect on fruit size. In this paper we registered the first records of R. canina and R. rubiginosa as host plants for M. aculeatus in wild areas of Argentina and we verified the absence of the wasp in R. multifl ora fruits. In R. canina the percentage of infected fruits by M. aculeatus was low (0-1 % per site) not being probably a conditioning factor of its actual reduced spread. In R. rubiginosa, the percentage was high (31-75 % of infested fruits per sites), but only the 2-8 % of achenes were infected. Considering the analyzed sites, the distribution of M. aculeatus infestation at regional level in rose studied species was reduced. The fruit size was not affected by the insect infestation. The results of this work show a low actual impact of M. aculeatus in the control of rose invasion at Andean region of Argentina. However, since M. aculeatus populations could be affect by the temperature, a change of this variable could increase the seeds infestation prevalence in the medium and long term.
Key words:
infestation, invasive shrubs, torymid wasp, wild roses

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