Patterns of seed predation by vertebrate versus invertebrate seed predators among different plant species, seasons and spatial distributions.

Abstract

Experiments were conducted to examine how the relative importance of two broad groups of seed predators, insects and mammals, changes depending on seed species, habitat, and spatial and temporal distribution of seeds. Experiment 1 was conducted at La Selva Biological Station, Costa Rica, to investigate if seed predation by insects and mammals change within forest sites with fruiting season and distance from parents. Experiment 2 was conducted in La Selva and Gigante Peninsula, Peru, to investigate if seed predation by insects and mammals change between forest sites with fruiting season and distances from parents. Socratea exorrhiza, a single large-seeded palm species, was observed in the first two experiments. Experiment 3 was conducted in Peru to investigate how are insect and mammal seed predators influenced by forest disturbance and plant species. Seed predation by insects and mammals was not affected by date of placement in a similar manner at either La Selva or Gigante. Distance from the parent tree did not influence predation by insects at either La Selva or Gigante. In contrast, predation by mammals was greater near the parent tree both at La Selva and at Gigante in May. Seed survival was generally higher at Gigante that at La Selva, and the relative importance of insect and mammal seed predators was very different between these two sites. Species-specific differences in predation were not consistent between insects and mammals and species with the highest levels of seed predation by mammals did not have the highest levels of insect seed predation. Although predation by mammals was not different between young and mature forest, insect predation was significantly greater overall in mature forest. Despite the general trend of higher insect predation in disturbed forest, there was still considerable variation among species in the relative importance of mammal and insect predation in young and mature forest.

Seed fate and seedling dynamics after masting in two African rain forest trees

“…Squirrels for example can distinguish between viable and unviable (i.e., infested or aborted) seeds of a temperate pignut hickory tree (Carya glabra), preferring to take the former (Sork and Boucher 1977). Seed mortality of the neotropical palm Socratea exorrhiza due to mammal predation was twice as fast as that caused by insects (Notman and Villegas 2005); however, we could not evaluate removal every 2-3 days in such a large study area. Given the propensity for greater fungal and insect activity during the rainy seasons in tropical rain forests (Givnish 1999), an adaptive ability of seed predators to quickly discriminate among fast-germinating food sources is vital (Jansen et al 2004).…”

Hunting-induced defaunation drives increased seed predation and decreased seedling establishment of commercially important tree species in an Afrotropical forest

“…Mammalian seed predators, particularly rodents, are often implicated with causing the greatest seed mortality overall (Hulme, 1998;DeMattia et al, 2004;Notman and Villegas, 2005). Because changes in mammal composition and abundance can affect seed and seedling predation (Asquith et al, 1997;DeSteven and Putz, 1984;Sork, 1987), hunting may alter patterns of tree recruitment in defaunated forests, but the effects are not clear.…”

Pine seed removal in fragments of three temperate plant communities

“…In accordance with Hulme (1997) and Hulme & Kollmann (2005) seed removal by insects can be determined by vegetation structure. Trees represent physical barriers that obstruct the movement of seeds by insects increasing the energy expenditure (Crist & Wiens 1994, Notman & Villegas 2005. However, other factors such as seed production phenology (Schafer et al 2006) and high temperatures of the soil during the day in open areas (Briese & Macauley 1980, Sudd & Franks 1987 also are involved.…”

“…The species composition and seed availability determines the movement of granivores among different types of plant communities to find food resources and consequently to impact plant communities (Hoshizaki & Miguchi 2005). Accordingly the interaction between plants and granivores can have reciprocal effects, for example, if the plant composition changes, the structure and composition of granivores also change and vice versa (Meiners & Stiles 1997, Hulme & Kollmann 2005, Notman & Villegas 2005.…”

“…However under high risk, rodents also use open areas for foraging, but stay near wooded areas if they require shelter (Whelan et al 1991). Insects can be spatially more limited because they avoid sites with dense vegetation that represents an obstacle in seed removal (Crist & Wiens 1994, Notman & Villegas 2005 and prefer to remove seeds during the night because during the daytime the soil temperature is higher (Crist & MacMahon 1991).…”