Gordon W. Frankie

A new classification for plant phenology based on flowering patterns in lowland tropical rain forest trees at La Selva, Costa Rica

A new classification and conceptual framework for plant phenology are proposed to resolve problems in describing tropical patterns. A long-term (12 yr) survey of flowering in 254 lowland tropical rain forest trees of 173 species from the La Selva Biological Station in Costa Rica showed highly diverse, irregular, and complex patterns. Analysis of this survey data relied primarily on graphical analyses that provide data representation methods rather than numerical summaries that provide data reduction methods. The classification differs from previous ones in three ways. It uses, as the primary criterion, frequency of the time series, based on explicit time and amplitude scales, so that irregular temporal sequences are revealed. It features a system of subsidiary classes based on other quantitative descriptors: regularity, duration, amplitude, date, and synchrony. Finally, the conceptual framework separates patterns at each level of analysis so that adding the time series at one level produces a time series for the next higher level. Levels are hierarchical from the flower to the individual, population, and community with additional non-nested levels such as the guild. The four basic classes-continual, subannual, annual, and supra-annual--are applied to patterns at any level of analysis. The classification system provides a logical framework for quantitative description of phenological behavior leading to more standardized comparisons. Thus we can see that tropical phenology differs from temperate phenology in two major ways. In tropical species, the nature of the pattern may change from one level of analysis to the next, which is not typical of temperate species. In many tropical species, phenological patterns vary more widely over the geographic range of a species than they do in temperate species.

Comparative phenological studies of treelet and shrub species in tropical wet and dry forests in the lowlands of Costa Rica.

SUMMARY (1) During 1970-73, marked individuals of 154 treelet and shrub species at a Wet forest site and 95 species at a Dry forest site in Costa Rica were observed regularly at 4- to 6-week intervals for changes in leafing, flowering and fruiting. (2) All the shrubs in the Wet forest were evergreen. New leaves were produced continually throughout the year by half the species, although this behaviour was more pronounced in species of secondary forest (87%0). For the community as a whole, leaf production was equable throughout the year. (3) About half of the treelets and shrubs in the Dry forest were deciduous. Hill forest treelets and shrubs produced most leaves at the beginning of the wet season, Riparian forest treelets and shrubs had a peak in leaf production near the end of the wet season, and leafing of species of secondary forest was continuous throughout the wet season. Most treelets and shrubs were bare or dormant during the dry season. Leaf loss was greatest during February. (4) There were no consistent peaks of flowering for treelet and shrub species in the Wet forest, but flowering levels tended to be greatest in the first half of each year. (4) Continuous flowering was rare among Wet forest treelets and shrubs, being characteristic of only a few species of secondary forest. Most Wet forest treelets and shrubs (64%) had several flowering episodes each year, with the episodes separated by 3-5-month intervals. Species with only a single brief synchronous flowering period were rare. (6) By contrast, flowering amongst Dry forest treelets and shrubs showed a pronounced seasonal pattern. The Hill forest treelet and shrub community had a sharp peak of flowering at the beginning of the wet season, while, in contrast, the Riparian forest treelet and shrub community had its major flowering at the end of the wet season. Most Dry forest species flowered synchronously once or twice each year. (7) There was a weak tendency for maximum fruiting of Wet forest shrubs in the second half of each year. A short period of fruit maturation (4 months) was shown by most Wet forest treelets and shrubs, although one species had a fruit maturation time of 27 months. Ten species of Wet forest treelets and shrubs flowered at least once during the study, but failed to produce fruit.

Rainfall as a factor in the release, timing, and synchronization of anthesis by tropical trees and shrubs

Although a number of studies have described seasonality of flowering by tropical plants (most often trees) either at the species or community level, for tropicalplants there have been few studies treating the induction of reproductive structures, their ensuing development, or the triggering of anthesis (opening of the flower). In this paper we present data which demonstrates that rainfall, either directly or indirectly, is an important timing and spacing mechanism for the flowering of at least some tropical plants. We also attempt to relate this phenomenon to some prior relevant studies on flowering in the tropics.

Reproductive biology of some Costa Rican Cordia species (Boraginaceae).

Reproductive features of eight Cordia species (Boraginaceae) from the seasonally dry Pacific slope of Costa Rica are described. Components of the floral, pollinatory, breeding, and seed-dispersal systems of each species are interactive. Two sets of syndromes are recognized: one consisting of floral, pollinatory, and breeding-system traits; the other composed of growth form, habitat preferences, and seed-dispersal traits. Within the genus, in the Neotropics, there has been a radiation from an ancestor presumably characterized by a basic chromosome number of 8, heterostyly, and fleshy fruitedness. Within the separate lines that have diverged in respect of the second syndrome, episodes of polyploidization have occurred as well as chromosomal loss (aneuploidy). Homostyly and dioecism have appeared several times in Cordia, in different lines. Comparisons with the reproductive characteristics shown by Cordia species in two other neotropical communities reveal no contradictions to the generalizations drawn from the Pacific slope results. As PART OF AN EFFORT to understand the evolutionary changes and selective pressures that have brought about the kinds of reproductive adaptations which are to be seen in tropical forests, we have subjected the genus Cordia to an intensive investigation. The eight species of Cordia in the seasonally dry Pacific lowlands of Guanacaste Province, Costa Rica, were chosen for investigation (table 1). Cordia contains a number of common species that present a wide array of breeding systems, ranging from homostyly to heterostyly and dioccy, including flower morphs adapted for varied pollinatory assemblages, and utilizing both wind and animal seed dispersal. Our objective is to quantify, as far as possible, the critical aspects of phenology, floral and pollination biology, breeding system, and seed-dispersal strategy of different Cordia species, to attempt to discern correlations between these features, to interpret their ecological importance, and finally to point out evolutionary shifts which appear to have taken place as well as the selective pressures which may have produced them. DISTRIBUTION Gentry and Janos (1974) have summarized the Central American distribution of Cordia, and additional information is to be found in the work of Johnston (1949a,b, 1950). All eight Guanacaste Cordia species are widespread through most of Central America, presumably at drier sites (with the exception of C. alliodora which occurs up to 1000 meters and is found on the wet Atlantic slope as well). The distribution of Cordia alliodora and C. gerascmnthas extends northward into Mexico, while Cordia inermis and C. pringlei extend southward to northern South America. Most of the species also occur on several islands in the Caribbean.

Ecological Patterns of Bees and Their Host Ornamental Flowers in Two Northern California Cities

Abstract A survey of the bee species and their ornamental host flowers that occur in residential neighborhoods of the cities of Albany and adjacent Berkeley in northern California was conducted from 1999–2003. A simple bee frequency (visitation) count was developed to evaluate the relative attraction of bees to their host flowers. Results of the survey revealed that 76 species of bees, mostly natives, from five families, visited 129 host plants at measurable levels. The most common host plant families were Asteraceae, Lamiaceae, Polygonaceae, Rosaceae, and Scrophulariaceae. Honey bees and all other bee taxa were recorded separately on host plants, and both bee groups were more attracted to California native plants than exotics on a percentage basis. Variable attraction was recorded within native and exotic host plants, and a large part of this variation appears related to where the plants are found in residential areas. In general, the highest bee diversity and abundance was observed in diverse gardens having a high number of bee-attractive plants flowering at the same time. Ground nesting by several species was also noted in diverse and other garden sites. Overall, many bee species seem pre-adapted to use extant urban resources for forage, reproduction and survival in residential areas of these two California cities.

Detecting Insect Pollinator Declines on Regional and Global Scales

Recently there has been considerable concern about declines in bee communities in agricultural and natural habitats. The value of pollination to agriculture, provided primarily by bees, is >

Urban Forests and Insect EcologyComplex interactions among trees, insects, and people

200 billion/year worldwide, and in natural ecosystems it is thought to be even greater. However, no monitoring program exists to accurately detect declines in abundance of insect pollinators; thus, it is difficult to quantify the status of bee communities or estimate the extent of declines. We used data from 11 multiyear studies of bee communities to devise a program to monitor pollinators at regional, national, or international scales. In these studies, 7 different methods for sampling bees were used and bees were sampled on 3 different continents. We estimated that a monitoring program with 200-250 sampling locations each sampled twice over 5 years would provide sufficient power to detect small (2-5%) annual declines in the number of species and in total abundance and would cost U.S.

Nesting-habitat preferences of selected Centris bee species in Costa Rican dry forest

2,000,000. To detect declines as small as 1% annually over the same period would require >300 sampling locations. Given the role of pollinators in food security and ecosystem function, we recommend establishment of integrated regional and international monitoring programs to detect changes in pollinator communities.

Seasonality in Bees and Their Floral Resource Plants at a Constructed Urban Bee Habitat in Berkeley, California

forests recede under the pressures of a growing human population, an increasing proportion of the worlds trees will be found in urban areas. These trees are exploited by insects and people, and the interactions among trees, insects, and humans are often complex. By altering plant diversity, introducing exotic species, polluting the environment, and placing trees under stress, people have increased the distribution and abundance of insects considered to be pests. In this article, we review research on human influences on the ecology of urban forest insects.

CHEMICAL ECOLOGY OF BEES OF THE GENUS CENTRIS (HYMENOPTERA: APIDAE)

Solitary bees are known to be important pollinators of seasonal dry forest plants in Costa Rica. Recent assessments of the genus Centris (family Anthophoridae) and other solitary bee taxa indicate that populations of these bees have declined by 85-90 percent in this forest over the past 20 yr. Deforestation, wildfires, and conversion of forest land to agriculture are the main reasons for the decline. From 1987 to 19901 we studied the preferred nesting habitats of seven Centris species that specialize in making their nests in preexisting holes in dead trees. Special wooden sampling units, with preexisting standardized holes, were systematically placed in several habitat types in the Lomas Barbudal Biological Reserve, Guanacaste Province