Factors limiting seed germination and seedling establishment of the hemiepiphyte Ficus stupenda were investigated with two field experiments conducted in a Bornean rain forest canopy. In Experiment 1, seeds of F. stupenda were planted in potential establishment sites averaging 31 m above the ground in each of 45 dipterocarp trees. Twenty seeds each were planted in a total of 336 sites. Germination, survivorship, and growth were monitored over 1 yr, and examined in relation to microsite and host tree characteristics. The presence of substrate with good moisture retention (soil, rotting wood, or moss) was the most important factor for germination. Such substrates were most frequently associated with knothole sites in the canopy, which had the highest level of establishment success. Seedling survival to 12 mo was low (1.3% of planted seeds), especially considering that the best available sites in each tree were selected. Only 0.04% of seedlings showed vigorous growth after 12 mo. A seed—harvesting ant in the genus Pheidole significantly reduced germination success, and herbivory and desiccation killed many seedlings at later stages. In Experiment 2, seedling growth in natural canopy sites was compared with growth of seedlings in artificial planter boxes raised into the canopy in order to assess the relative quality of canopy sites. Planters were superior to natural sites for seedling survivorship and supported much more rapid seedling growth with a positive response to light level. Higher growth rates in planters compared with natural sites showed that water stress appeared to be the critical factor limiting seedling growth in the canopy, even in this very wet climate. Sites in the canopy with the optimal combination of conditions for fig seedling establishment appear to be very scarce. Ficus population densities may be limited by both biotic and abiotic factors reducing early recruitment success.

Ornaments used in courtship often vary wildly among species, reflecting the evolutionary interplay between mate preference functions and the constraints imposed by natural selection. Consequently, understanding the evolutionary dynamics responsible for ornament diversification has been a longstanding challenge in evolutionary biology. However, comparing radically different ornaments across species, as well as different classes of ornaments within species, is a profound challenge to understanding diversification of sexual signals. Using novel methods and a unique natural history dataset, we explore evolutionary patterns of ornament evolution in a group—the birds-of-paradise—exhibiting dramatic phenotypic diversification widely assumed to be driven by sexual selection. Rather than the tradeoff between ornament types originally envisioned by Darwin and Wallace, we found positive correlations among cross-modal (visual/acoustic) signals indicating functional integration of ornamental traits into a composite unit—the “courtship phenotype.” Furthermore, given the broad theoretical and empirical support for the idea that systemic robustness—functional overlap and interdependency—promotes evolutionary innovation, we posit that birds-of-paradise have radiated extensively through ornamental phenotype space as a consequence of the robustness in the courtship phenotype that we document at a phylogenetic scale. We suggest that the degree of robustness in courtship phenotypes among taxa can provide new insights into the relative influence of sexual and natural selection on phenotypic radiations.

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