Bruchid beetle infestation and the value of Attalea butyracea endocarps for neotropical rodents

Abstract

Frugivorous and granivorous vertebrates often discriminate against seeds and fruits infested by insects (Sallabanks & Courtney 1992). Insects may actively render seed or fruit unpalatable or unusable to vertebrates as a strategy to maximize the amount of food available to themselves (Janzen 1977). Nevertheless, vertebrates sometimes do not differentiate between sound and infested seeds or fruits (Dixon et al. 1997, Weckerly et al. 1989), or even prefer insect-infested seeds and fruits to sound ones (Sallabanks & Courtney 1992, Semel & Andersen 1988, Steele et al. 1996, Valburg 1992). Possible reasons for vertebrates to prefer infested seeds include: (1) seeds with larvae having a higher nutritional value than sound ones, because larvae synthesize fat and/or proteins (Sallabanks & Courtney 1992, Valburg 1992) or other nutrients such as vitamins (Havera & Smith 1979, Semel & Andersen 1988, Steele et al. 1996); (2) seeds with larvae tasting better than sound seeds (Borowicz 1988); and (3) seeds with larvae may be more easily opened and consumed than sound seeds (Borowicz 1988).

Defaunation affects Astrocaryum gratum (Arecales: Arecaceae) seed survivorship in a sub-montane tropical forest

“…and Proechimys spp., were difficult to identify and therefore were gathered in a single group. Because small holes are indicators of insect predation, we also noted holes in the endocarp (Silvius, & Fragoso, 2002;Galvez, & Jansen, 2007). We recorded rotten, attacked by fungus or nonviable seeds, based on the exterior seed appearance and finally the inviability of the seed.…”

“…When dispersed long distances, seeds had higher survivorship with lower interspecific competition and invertebrate infestation; e.g., Coleoptera; Bruchids, Scolytine. (Janzen, 1970;Quiroga-Castro, & Roldán, 2001;Galetti, Donatti, Pires, Guimarães, & Jordano, 2006;Galvez, & Jansen, 2007;Dracxler et al, 2011).…”

“…Many tropical wildlife including mammals, birds and insects are known seed predators (Smythe, 1989;Dracxler et al, 2011). Therefore, the composition of the animal fauna in a forest will have different impacts on seed survivorship, and the removal of medium to large mammals by over-hunting or habitat loss, will have different effects on tree populations and the structure of the forest (Roldán, & Simonetti, 2001;Silman, Terborgh, & Kiltie, 2003;Wright, 2003;Beckman, & Muller-Landau, 2007;Galvez, & Jansen, 2007;Holbrook, & Loiselle, 2009;Dracxler et al, 2011).…”

Digestibility of palm seeds and bruchids larvae by Neotropical rodents

“…For the endocarps of A. butyracea, Gálvez and Jansen (2007) found indirect evidence that rodent foragers do not discriminate between infested and non-infested endocarps. This result is superficially surprising considering the fact that on average, seeds contain more energy than larvae.…”

“…Gálvez and Jansen's study suggested that rodents show no preference for either type of endocarp because of a trade-off effect; the infested endocarps with less energy can be opened more easily than the non-infested endocarps that contain higher energy content. Building on the study by Gálvez and Jansen (2007), I studied the trade-off hypothesis and compared the relationship of metabolizable energy content over time of handling (M/t) for both types of endocarps.…”