Groves versus isolates: how spatial aggregation of Astrocaryum murumuru palms affects seed removal

Abstract

Palm seeds of the genus Astrocaryum are known to attract a wide range of seed predators, including insects, rodents and peccaries. We investigated the removal of seeds of Astrocaryum murumuru var. macrocalyx in dense groves and under solitary palms, both within and outside of peccary exclosures. We set out arrays of 40 seeds at each of 40 sites representing four treatments: in the open and in peccary exclosures, in groves and under solitary palms. Seed removal from each site was monitored daily for 55 d. Infra-red-triggered cameras were installed to identify the species that removed seeds. From the known and hypothesized behaviour of vertebrate seed predators under various circumstances, we predicted that (1) overall seed loss should be higher under solitary trees, (2) peccaries should forage preferentially in groves, (3) the variance in the rate of seed removal should be higher in groves, (4) a greater fraction of the seeds removed from solitary palms should be scatterhoarded, and consequently, (5) greater numbers of seedlings should recruit near solitary palms than in groves. The first four of these predictions were confirmed and the last was rejected by the results. Peccaries preferred to forage in groves, and small rodents preferred to forage under solitary palms. Whether in groves or under solitary palms, peccaries preferentially removed seeds from large arrays (21–40 seeds), and mostly ignored small arrays (≤ 20 seeds). Camera trapping demonstrated that the most frequent visitors to seed arrays were Myoprocta pratti and Proechimys spp. There was no significant difference in the numbers of seedlings around trees in groves versus solitary trees.