Predation and dispersal of large and small seeds of a tropical palm

Abstract

Seed size may vary greatly among individuals within plant species. What effects the extremes of this variation have for seeds taken by small mammals are poorly understood. Not all seeds removed by small mammals are necessarily eaten. Small rodents are common seed predators, but they may disperse a significant proportion of seeds by scatter hoarding them via burial. Size‐dependent predation and dispersal of seeds has not been directly tested within a plant species for tropical rodents. This study tested whether or not large and small nuts of Astrocaryum mexicanum (Palmae) differed in their fates due to handling by the spiny pocket mouse Heteromys desmarestianus (Heteromyidae). Exclosures were used to give small rodents exclusive access to A. mexicanum nuts. H. desmarestianus preferentially consumed large over small A. mexicanum nuts, but cached (in burrows and by scatter hoarding) similar proportions of these nuts by size. Small nuts tended to be buried farther away from exclosures than large nuts. Although sample sizes of buried nuts were small, the rodents retrieved all buried large nuts, but 30% of the small nuts remained buried long enough to germinate. I also examined predispersal predation by insects and found that insects appear to have no size preference for A. mexicanum nuts, but insect predation appears to hinder nut development. Thus, nuts attacked by insects develop to be significantly smaller, with a low proportion of undamaged endosperm, than uninfested nuts. It is hypothesized that the preferential predation of large A. mexicanum nuts by H. desmarestianus is a response by these rodents to insect predation.

Anthropogenic disturbances jeopardize biodiversity conservation within tropical rainforest reserves

“…Indeed, small rodents and squirrels disperse the seeds of A. mexicanum (40). In Belize, up to 30% of A. mexicanum seeds removed by mice were buried in the ground but subsequently germinated (41). Similar behavior has been observed in agouties that remove seeds of Astrocaryum standleyanum in Barro Colorado Island (42).…”

Propagule size and predispersal damage by insects affect establishment and early growth of mangrove seedlings

“…Several studies have found that the risk of predation by insects or small mammals increases with seed size (Thompson 1987;Reader 1993;Moegenburg 1996;Brewer 2001; but see Eriksson 1999) However, a recent model of the co-evolution of seed size and seed predation (Geritz 1998) predicts an evolutionary stable strategy consisting of a continuous range of seed sizes, with small seeds tending to be attacked more frequently than large seeds. In our system, we observed little or no correlation between rates of insect attack and propagule size.…”

How plants manipulate the scatter-hoarding behaviour of seed-dispersing animals

“…fat or tannin content) can alter this general pattern (Xiao & Zhang 2006;see below). Larger nuts and seeds are usually carried greater distances to cache sites (Hallwachs 1986;Vander Wall 1995;Jansen et al 2002Jansen et al , 2004Xiao et al 2004Xiao et al , 2005aTakahashi et al 2007;Zhang et al 2008); however, a few studies (Brewer 2001;Xiao et al 2004) have failed to observe this behaviour. Large nuts also have longer residence times in caches ( Jansen et al 2002), and large nuts often demonstrate increased fitness ( Jansen et al 2004).…”