oa African Entomology - Resource manipulation through architectural modification of the host plant by a gall-forming weevil Urodontus scholtzi Louw (Coleoptera: Anthribidae)



The manner in which a gall-inducing weevil, Urodontus scholtzi Louw, influences the growth pattern of its host plant, Galenia africana (Aizoaceae), was studied in Namaqualand, South Africa. Galled stems increased by twice the diameter relative to paired ungalled stems in the first and second years and by more than three times in the third year after galling. Stems opposite or distal to the galled stem frequently died, reaching 54 % mortality of opposite stems after one year and over 80 % after three years. Although the weevils have a two-year life cycle, the dominance of galled stems persists for at least four years and probably indefinitely. Resources are manipulated by the weevil when first instar larvae cut partially through vascular tissue, and by an unknown method of creating a strong sink for resources flowing up the stem. Survival in the gall was remarkably high at all sites, with 84-75 % of galls containing adult weevils.


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