The exotic weevil Stenopelmus rufinasus Gyllenhal, 1835 (Coleoptera: Curculionidae) across a "host-free" pond network

The exotic weevil Stenopelmus rufinasus Gyllenhal, 1835 (Coleoptera: Curculionidae) across a “host-free” pond
network
The presence of the exotic weevil Stenopelmus rufinasus (Coleoptera: Curculionidae) is closely related to the occurrence of
the exotic red water fern, Azolla filiculoides. In this paper, we present the first records of S. rufinasus in Doñana National
Park (SW Spain), based on sampling of macroinvertebrates in 91 temporary ponds, including monthly samples of 22 ponds,
during two successive years (2005-2007). The exotic weevil was present in 21% of the sampled ponds where the host plant, A.
filiculiodes, was not detectable. Because A. filiculoides can reach high densities in an adjacent area of marsh, we suggest that
the occurrence of the exotic weevil in these ponds is a consequence of dispersal from nearby marshes. Our study demonstrates
that S. rufinasus adults can occur at relatively high densities in ponds where the host plant is not present, suggesting that such
apparently “host-free” sites may act as stepping stones for the spread of this species.