Flowering patterns are defined by the timing, duration, and frequency of flowering. Plants, particularly in the tropics, vary enormously with respect to these main variables of flowering. We used data from 302 tree species in a wet tropical forest to test a series of predictions regarding timing, duration, and frequency of flowering and examined the effect of each variable on the other two. Because timing, duration, and frequency of flowering can be constrained by phylogeny, we analyzed the data before and after considering phylogenetic effects at the level of family. Flowering activity peaked in the first wet season from May to July, refuting our prediction of peak flowering during the dry season. Our prediction that most species should flower several times a year was supported when species flowering more or less continually throughout the year were included in this category. Our prediction that supra-annually flowering species should be the least frequent was also supported with some qualifications. As we predicted, species flowering several times a year bloomed relatively briefly per flowering episode. Our prediction of shorter flowering duration for species flowering in the dry season and for those with a temporal separation between flowering and vegetative growth was also supported. Furthermore, supra-annually flowering species flowered for a shorter duration than annually flowering species and had a higher probability of flowering in the dry season compared to episodically or annually flowering species. Phylogeny significantly constrained variation in flowering frequency, but not in flowering time or duration, among confamilial species.

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Based on data from observations of 302 tree species at La Selva, Costa Rica, we tested a range of hypotheses about the relationship between flowering parameters such as time, frequency, and duration and ecological features such as successional status, habit, sexual systems, and pollen vectors with and without considering the effect of family membership. We predicted that early successional species would flower any time of the year, but species pollinated by different vectors as well as dioecious species would flower nonrandomly across seasons. However, there was little evidence that flowering time varied with successional status, pollen vectors, and sexual systems. As we predicted, supra-annual flowering was proportionately less common in early successional species as compared to late ones, in understory species as compared to canopy species, and in dioecious species as compared to those with hermaphroditic flowers. When considering phylogeny, however, supra-annual flowering in the understory was not as rare as predicted. Our prediction of longer flowering in the early successional species as compared to late successional species was also supported. Predictions about longer flowering of dioecious species as compared to hermaphroditic species and of species pollinated by generalist vectors as compared to the specialists were not supported, though there was a trend in the expected direction.

Ecological and evolutionary studies typically consider variation in single reproductive characters in isolation, without considering how they might be correlated with other reproductive and vegetative characters. In our study, we examined temporal patterns of variation and correlation in flower diameter and fruit length during a reproductive phase in two Massachusetts populations of the herb, Chelidonium majus. We also examined the relationships of such variation to measurements of seed yield components (mean seed weight and number per fruit) and aspects of plant vegetative size. Most of the variation in the sizes of reproductive characters occurred within individual plants, instead of among plants or between populations. Flower and fruit sizes as well as seed number per fruit declined significantly during the season in both populations. Only mean seed size per fruit was relatively stable for individual plants in both populations. Conserving resources by a gradual reduction in the size of reproductive characters over the season may be a strategy for maternal plants to continue seed production. The strong, persistent patterns of correlation between certain characters, such as flower and fruit size, in spite of extensive phenotypic plasticity, was interpreted as indirect evidence for developmental correlation. Furthermore, vegetatively larger plants produced not only more flowers and fruits, but also consistently larger flowers and fruits. The results emphasize that variation in fitness characters, such as seed size and number, should not be viewed in isolation from vegetative characters, flower, and fruit sizes in ecological and evolutionary studies, if the goal is to understand the mechanisms of natural selection in wild populations.

Because of the complexities of their flowering parameters, it is difficult to make generalizations about flowering phenology among temperate angiosperms. We examined patterns of flowering time and duration among 2867 Korean angiosperm species, and these patterns were associated with climatic factors. The effect of taxonomic membership was also tested. Overall data pooled over species from 165 families showed that 63.8% of these angiosperms flowered in summer, 19.5% in spring, 16.5% in autumn, and 0.2% in winter. Summer and autumn flowering periods were significantly longer than springtime events. Both mean monthly temperature and precipitation were strongly positively correlated with the number of species in flower, but not with flowering duration. The seven largest families differed in their flowering season and duration; both parameters were also segregated among genera within large families. In a two-way analysis, both flowering season and family membership exerted significant effects on flowering duration. These results demonstrate that the evolutionary influence on flowering time and duration can be observed at the community level when two factors are considered, i.e., the interaction of flowering parameters and the taxonomic composition of species within those communities.

The sex ratio and spatial structure of different sexes are major components that affect the reproductive success and population persistence of dioecious plants. The differential reproductive costs between male and female plants are often believed to cause a biased sex ratio and spatial segregation of the sexes through slower growth and/or lower female survivorship. In this study, we examined the sex ratio and spatial structure of one population of Torreya nucifera trees in Jeju Island, Korea. We also tested the effects of the current tending actions in relation to tree vitality. At the population level, the sex ratio of the 2,861 trees was significantly biased toward males; however, it also showed considerable variation among different diameter at breast height classes and across habitats according to terrain level (from upper to lower). In 1999, before tree management (tending) began, among the ecological traits examined, only climber coverage correlated with tree vitality. Intensive tending such as climber removal since 1999 clearly enhanced the vitality of the majority of trees, but its effects were more conspicuous in medium-sized trees than in small ones, in upper terrain trees than those in other terrains, and in females than in males. Both male tree domination in small and large trees and tending effects on females are likely to reflect the effects of female reproductive costs regarding growth and/or survivorship. Spatial segregation between males and females was not observed in T. nucifera. Habitat heterogeneity created by the forest's rocky ground and its implications regarding sex ratios and spatial structure require further studies.

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