The structure of ground beetle assemblages (Coleoptera: Carabidae) at fruit falls of Melastomataceae trees in a Brazilian terra firme rain forest

Abstract

Although most Carabidae are recognized as predacious, recent studies have shown that some tropical rain forest Carabidae use the small seeds of fallen fruit from some tree species as a key food resource (particularly figs [Moraceae] but also those from other families). Assemblages of carabid beetles (Coleoptera: Carabidae) at fruit falls of the Melastomataceae tree genera, Bellucia, Loreya, and Miconia, were studied in a terra firme rain forest near Manaus (Amazonia, Brazil) from February 1992 to August 1996. Of 5483 specimens of 14 carabid species collected at 53 fruit falls, 98.2 percent of the collected beetles represented the seed-feeding genus Notiobia. Four of the 7 Notiobia species were found to reproduce at Melastomataceae fruit falls. The most abundant species, N. glabrata, was found to be a Melastomataceae seed generalist, while N. maxima seemed to prefer the seeds of Bellucia, and N. aulica and N. umbrifera the seeds of Miconia. The presence of larvae indicated reproduction of N. glabrata at fruit falls of all three tree genera and reproduction of N. maxima at those of Bellucia. Fruit falls of different species and genera of Melastomataceae appeared to occur at different times of the year and not continuously throughout the year. The seed-feeding Notiobia species, which specialize on Melastomataceae, used fruit falls of figs as migratory "stepping stones" during periods when there were no Melastomataceae fruit falls. The comparable suite of fig seed-feeding specialist species of Notiobia did not appear to do the reverse and seemed to avoid Melastomataceae fruit falls. The carabid assemblage at fig fruit falls was more diverse than the assemblage at those of Melastomataceae. Among the Melastomataceae, carabid species richness was highest at Miconia fruit falls and lowest at Loreya fruit falls. The three most common predatory species caught at Ficus fruit falls were also caught at those of Melastomataceae and appeared to reproduce at both fruit fall types. The proportion of the carabid assemblage accounted by predatory species was much lower at Melastomataceae (1.8%) than at fig fruit falls (8%).