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A study of the relation between light and the phenology of tropical trees indicates that tree phenologies are consistent with the hypothesis that leaf and flower production have been selected to coincide with peak irradiance in the presence of water. An alternate hypothesis that leaf and flower production have been selected to coincide with minimal pest levels is also worth consideration. The research is inconclusive, and more data would be needed on insect and irradiation seasonalities to evaluate further possibilities.

To resolve the controversy initiated by Connor and Simberloff's (1978) analysis of similarity among the biota of the Galapagos Islands, we analyze the theoretical relationship between interspecific interactions and similarity. A counterintuitive result from our analysis is that all interspecific interactions, including competition, tend to increase similarity (given their effects on unconditional probabilities of occurrence). To have this effect, however, they must combine with the effects of interisland colonization. The results of Power (1975) and those of Connor and Simberloff (1978) suggest that interisland colonization and possibly interspecific interactions have had important effects on similarity in the Galapagos, but several difficulties prevent us from accepting their results. We conclude, with Connor and Simberloff, that the similarity of bird species lists for the Galapagos Islands does not support the importance of interspecific interactions in determining species distributions. In general, we conclude that although a combined positive effect of interisland colonization and all types of interspecific interactions on similarity might be detectable using a modification of Connor and Simberloff's approach, the effects of these phenomena cannot be disentangled to provide evidence for or against the importance of competition. [ABSTRACT FROM AUTHOR]

There are several reasons for questioning whether derivations of species-area relations from species-abundance distributions apply to insular communities. First, the derivations assume that the summed density of individuals of all species is a constant. In fact, in most archipelagos this quantity varies systematically with island area (Wright 1980). Second, the appropriate species-abundance distributions may not occur on islands. The logarithmic series is characterized by large numbers of very rare species, an unlikely event when there are barriers to immigration. Derivations from the negative binomial assume that a parameter is negative, but in fact it is positive for 102 of the 111 communities that have been analyzed. The lognormal systematically overestimates the abundances of the most common species, and if species-abundance distributions observed for small islands are lognormal, they are severely truncated. Finally, the parameters of species-abundance distributions and species-area relations do not agree for birds in the West Indies or on islands in Gatun Lake, Panama. These analyses do not suggest that species-abundance distributions determine species-area relations for insular communities. [ABSTRACT FROM AUTHOR]