PMC

Scanning electron microscopy images of the surfaces of fresh seeds (A, Apeiba; C, Luehea; E, Ochroma; G, Cochlospermum) and longitudinal sections of seeds (B, Apeiba; D, Luehea; F, Ochroma; H, Cochlospermum). Scale bar = 1 mm. An asterisk highlights the chalazal area when visible.

Scanning electron microscopy images revealing the time course of chalazal plug breakage over 5 days for Apeiba seeds (A–D) and Ochroma seeds (E–H). At the onset of the experiment, seeds of Apeiba (A) and Ochroma (E) previously determined as impermeable had no evidence of cracks on the chalazal area, and the chalazal plug was attached to the seed surface. When seeds were exposed to full sun over 5 days, a gradual release of dormancy was observed as a progressive lifting of the chalazal plug in seeds of Apeiba (B–D) and Ochroma (F–H). Scale bar = 1 mm.

Nearest neighbor power laws for 9 Barro Colorado Island (BCI) species, relating the log of distance in m to the nth nearest neighbor to the log of the rank of nearest neighbor, illustrating the uniformly high coefficients of determination of these relationships for BCI species. All census size classes are included (stems >1 cm dbh). Species shown: Apeiba membranacea (Tiliaceae), canopy tree, moderately light demanding; Brosimum alicastrum (Moraceae), shade tolerant; Cecropia insignis (Cecropiaceae), canopy tree, very light demanding; Faramea occidentalis (Rubiaceae), understory tree, shade tolerant; Gustavia superba (Lecythidaceae), midstory tree, shade tolerant; Quararibea asterolepis (Bombacaceae), canopy tree, shade tolerant, Simarouba amara (Simaroubaceae), midstory tree, moderately light demanding; Trichilia tuberculata (Meliaceae), canopy tree, shade tolerant; Virola sebifera (Myristicaceae), midstory tree, shade tolerant. Of the 217 species analyzed having >20 individuals in the plot, the power laws had coefficients of determination >0.999 in 50.7% (110) species, and >0.99 in 88.5% (192) species.

Effects of focal fungi on seed germination and viability. Bars represent the proportion of germinated (Left axes) or viable (Right axes) seeds after inoculation with each of four fungal isolates. Viable seeds are defined as the proportion of seeds that were alive (determined via the tetrazolium test, see ) but failed to germinate, plus seeds that germinated. Bar heights correspond to values normalized by the maximum number of germinated or viable seeds observed in controls (noninoculated seeds). In some cases, inoculated seeds of Trema micrantha “black” germinated more than control seeds, so proportions exceed 1. Because surface sterilization after inoculation did not influence the germination or viability of seeds (), bars include both treatments. Error bars represent SE. Fungal isolates were cultured from buried seeds that were viable (+) or inviable (−) from AM, Apeiba membranacea; AS, Annona spraguei; OP, Ochroma pyramidale; and TB, Trema micrantha “black.” Isolates 1 and 2 represent the same OTU at 99% sequence similarity, but different OTU at 100% sequence similarity ().