Colonization of fleshy-fruited plants beneath perch plant species that bear fleshy fruit

Abstract

We evaluated the contribution of seed dispersal by birds to the colonization of fleshy-fruited plants beneath plants that bear fleshy fruits and were used as perches by birds. Specifically, we investigated the composition of seeds and saplings sampled beneath nine fleshy-fruited perch plant species in a Pinus thunbergii stand on a coastal sand dune in central Japan. Both the numbers and the species numbers of bird-dispersed (pulpless) seeds differed significantly among the perch plant species. Nevertheless, the quantitative compositions of bird-dispersed seeds were similar among the perch plant species because of the significant positive interspecific correlations of species rank order in numbers of bird-dispersed seeds per species. Similar relationships were also found for saplings. For each perch plant species, the numbers of fallen conspecific seeds were significantly higher than or not different from those of heterospecific seeds. Furthermore, the numbers of pulpy seeds that fell directly from the perch plant were significantly higher than those of bird-dispersed conspecific seeds for seven of nine perch plant species. However, the densities of conspecific saplings were significantly lower than those of heterospecific saplings. Most pulpy seeds, therefore, probably do not germinate beneath their mother plants, and conspecific seeds probably accumulate in seed banks or are consumed by herbivores.

Is there a risk-dilution effect of naturally fallen fruits on post-dispersal seed predation by wood mice?

“…To determine the numbers of seeds and fruits to put in the baskets, we estimated means, maximums, and minimums of densities of bird-dispersed seeds and naturally fallen fruits per basket (Table 1) using data from 1.5-m 2 rectangular traps placed beneath fruiting plants of the seven species (n=10×7 species) at the same study site between 20 October 1999 and 7 January 2000 Kamitani 2003, 2004), which was a good mast year for these plant species. Because the composition of bird-dispersed seeds beneath plants was not affected by the species of plant on which birds defecated or regurgitated and was thus similar among plant species (Takahashi and Kamitani 2003), 21 seeds of the seven autumn-fruiting plant species (three seeds per plant species) were placed in each small basket (n=330). For the treatments with fruits, fruits of the same species as the fruiting plant overhead were placed in each large basket (around the small basket).…”