Removal of black palm (Astrocaryum standleyanum) seeds by spiny rats (Proechimys semispinosus)

Abstract

A seed-removal experiment was conducted to assess the role of Proechimys semispinosus (Central American spiny rat) as potential predator and disperser of Astrocaryum standleyanum (black palm) seeds. One hundred fresh ripe A. standleyanum fruits were placed in semipermeable cages on each of 14 small islands in Panama, and seed disappearance rates were calculated for each island. Spiny rat density and biomass were determined by live-trapping on each island for 5 consecutive days and 4 nights. Censuses of fruiting trees were conducted on each island to control for effects of food availability on removal of palm fruits. Disappearance rates were related positively to total spiny rat density, density of adult and subadult spiny rats, and spiny rat biomass, but the density of fruiting trees accounted for very little variation. Spiny rats evidently prey heavily on A. standleyanum seeds, based on the high removal rates and on feeding observations of captive individuals. Since spiny rats may scatterhoard A. standleyanum seeds, they may also function as effective seed dispersers if seeds are removed to favourable germination sites unavailable to other seed predators. Results indicate that spiny rats, because of their abundance and wide distribution, may be important but overlooked predators and dispersers of A. standleyanum seeds and of other large-seeded tree species.

Seed predation by rodents and safe sites for large-seeded trees in a fragment of the Brazilian Atlantic forest

“…Briefly, seed dispersal represents seed removal and discarding away from parental plants (Terborgh, 1990) and, in fact, it has been recognised as one of the most important factors affecting plant recruitment, spatial distribution, and long term persistence of plant populations (Terborgh and Nuñez-Iturri, 2006;Nuñez-Iturri and Howe, 2007). Benefits of seed dispersal include reduced seed predation and seedling mortality -escape hypothesis sensu Howe and Smallwood (1982); colonisation of new habitats (Redford, 1992;Corlett and Turner, 1997); seed release from fruits (Asquith et al, 1997); seed discarding in microhabitats suitable for seed germination (Howe and Smallwood, 1982;Hoch and Adler, 1997); seed burial (Forget, 1990); and enhanced seed-mediated gene flow (Jordano et al, 2007). A classic example from a Neotropical forest tree is the strict dependence of Bertholletia excelsa large-seeds, which must be released from an extremely hard pixidium and buried by agoutis in order to have higher chances of germination and successful recruitment (see Peres et al, 1997).…”

The genus Astrocaryum (Arecaceae)

“…The species of subsection Acaulia grow in semi-arid cerrado-vegetation in Brazil. Studies on population dynamics and dispersal have been made in Astrocaryum jauari (Piedade, 1984), A. standleyanum (Smythe, 1989;Hoch and Adler, 1997), A. sciophilum (Sist, 1989a,b;Charles-Dominique et al, 2003), A. paramaca (Forget, 1991), A. aculeatum (Nascimento et al, 1997), A. aculeatissimum (Galetti et al, 2006), and Astrocaryum spp. (as A. murumuru, Cintra, 1997;Cintra and Horna, 1997;Beck and Terborgh, 2002).…”

Seasonal dispersal of arbuscular mycorrhizal fungi by spiny rats in a neotropical forest

“…For example, the probability of tree seedling establishment and the subsequent distribution of adult trees are thought to depend largely on the inter-relationship between organisms that function as seed dispersers and those that serve as mortality agents (Janzen 1970;Connell 1971). Rodents are especially important in this regard because many species function as both seed dispersers (Smythe 1989;Forget and Milleron 1991;Adler and Kestell 1998) and as mortality agents via seed predation (Forget et al 1994;Hoch and Adler 1997;Adler and Kestell 1998). Such opposing roles exhibited by tropical rodents have been demonstrated experimentally to influence seed and seedling survival (DeSteven and Putz 1984;Smythe 1989;Terborgh and Wright 1994;Asquith et al 1997).…”