Comparison of four populations of Acanthoscelides obtectus (Coleoptera: Bruchidae) from different Colombian ecosystems

Abstract

The bean weevil (Acanthoscelides obtectus) and its preferential host plant Phaseolus vulgaris probably originate from Central or South America. Acanthoscelides obtectus populations have developed for many years in varied and relatively isolated ecosystems in these regions. The influence of the host and of copulation on reproductive activity was studied in four Colombian insect populations from medium (2000 m) and low altitudes (1200 m). Most medium altitude strains of females do not produce oocytes in the absence of hosts or of copulation. These external stimuli can still influence oogenesis after a long period. Virgin females of low altitude strains produce oocytes early in imaginal life and oviposit rapidly in the presence of the host or after copulation. These characteristics can be maintained for many generations. The different strains react differently to a change of thermoperiod. It is suggested that the strain differences are related to the climatic and ecological conditions prevailing at the various altitudes in the Andes; differences are also apparently related to the reproductive cycle of the host plant, which is ingested by the larvae.