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A vegetation classification approach is needed that can describe the diversity of terrestrial ecosystems and their transformations over large time frames, span the full range of spatial and geographic scales across the globe, and provide knowledge of reference conditions and current states of ecosystems required to make decisions about conservation and resource management. We summarize the scientific basis for EcoVeg, a physiognomic-floristic-ecological classification approach that applies to existing vegetation, both cultural (planted and dominated by human processes) and natural (spontaneously formed and dominated by nonhuman ecological processes). The classification is based on a set of vegetation criteria, including physiognomy (growth forms, structure) and floristics (compositional similarity and characteristic species combinations), in conjunction with ecological characteristics, including site factors, disturbance, bioclimate, and biogeography. For natural vegetation, the rationale for the upper levels (formation types) is based on the relation between global-scale vegetation patterns and macroclimate, hydrology, and substrate. The rationale for the middle levels is based on scaling from regional formations (divisions) to regional floristic-physiognomic types (macrogroup and group) that respond to meso-scale biogeographic, climatic, disturbance, and site factors. Finally, the lower levels (alliance and association) are defined by detailed floristic composition that responds to local to regional topo-edaphic and disturbance gradients. For cultural vegetation, the rationale is similar, but types are based on distinctive vegetation physiognomy and floristics that reflect human activities. The hierarchy provides a structure that organizes regional/continental vegetation patterns in the context of global patterns. A formal nomenclature is provided, along with a descriptive template that provides the differentiating criteria for each type at all levels of the hierarchy. Formation types have been described for the globe; divisions and macrogroups for North America, Latin America and Africa; groups, alliances and associations for the United States, parts of Canada, Latin America and, in partnership with other classifications that share these levels, many other parts of the globe.

The elegance of classification lies in its ability to compile and systematize various terminological conventions and masses of information that are unattainable during typical research projects. Imagine a discipline without standards for collection, analysis, and interpretation; unfortunately, that describes much of 20th-century vegetation ecology.

Environmental gradients, represented by mapped physical environmental variables within a GIS, were classified and used to allocate a two-stage random stratified sample for field survey of vegetation in the Mojave Desert Ecoregion, California. The first-stage sample was allocated randomly and with unequal proportions among 129 environmental classes defined by the intersection of climate and geology digital maps at 1 km resolution. The second-stage sample was selected for each 1 km cell in the primary sample by defining six terrain classes related to desert vegetation patterns and randomly locating one plot location per class per cell. The total number of observations (1133) was determined by the resources available for the survey. This approach allowed the vegetation survey to be planned efficiently, alternate samples to be located, and vegetation types to be defined quantitatively. The sample allocated surveyed broad scale environmental gradients effectively, and the objective of oversampling rare environmental classes and undersampling common classes was achieved in most cases. It did not succeed, however, in capturing replicates of rarer plant alliances. We suggest sampling efforts should be weighted even more heavily toward rare environments and plant communities for this objective.

The Barred Antshrike (Thamnophilus doliatus) is the most abundant insectivorous foliage-gleaning vertebrate in both closed rain forest and second growth on the island of Tobago. However, it occurs only in second growth on the larger neighbor island of Trinidad and on the neotropical mainland.Habitat niche expansion into Tobago forest has been facilitated by several behavioral traits which set the antshrike apart from other foliage-gleaners of forest and second growth on Tobago. The antshrike captures a higher diversity of foliage, branch & trunk, and terrestrial arthropods. It forages over a wider range of heights and under a wider variety of crown cover situations than any of its closest ecological counterparts on Tobago. The antshrike also takes a wider range of prey sizes and regularly uses additional food sources, including fruit and ants, not taken by other guild members. The broad foraging niche of the antshrike enables it to breed during many times of the year when other narrower-niched foliage-gleaners do not.On Trinidad, although the most common foliagegleaner in second growth, the antshrike was not observed in adjacent closed rain forest. Several facts suggest that diffuse competition may be excluding antshrikes from Trinidad forest: 1) a general pattern of rarity or absence in other parts of its range where there are more guild members; 2) more species and individuals of foliagegleaners with an overall higher biomass in Trinidad forest than in Tobago forest; 3) foliage arthropod resources are significantly (1.7x) lower in Trinidad forest than Tobago forest, suggesting that Trinidad forest guild members may be depressing the quantity of important resources for antshrikes; and 4) Trinidad forest species with the highest foraging similarity to antshrikes have a greater precentage of prey captures comprised of relatively specialized attack behaviors than do Tobago forest antshrikes.Foraging generalists like the Barred Antshrike appear to expand or contract their habitat niches depending upon the number of ecologically similar species in a given habitat. They may occur in high densities in habitats typically foreign to them provided competitors are few and there is sufficient food to supply their catholic requirements.

Three species of trees in the premontane forests of both Trinidad and Tobago have an extremely different coterie of fruit and seed consumers on each island. On Trinidad, legitimate dispersers comprised of principally frugivorous passerines were most abundant, whereas on Tobago seed-predacious parrots and chachalacas predominated. Significant morphological differences between Trinidad and Tobago in the fruits of the three plant species reflected the difference in consumers. Such characters as relatively thickened fruit walls, a higher frequency of multiple seeds and arils, and enlarged seeds were present in the Tobago populations, which were heavily preyed upon. The Tobago populations also had certain attractive features to legitimate dispersers, such as quantity of fruit pulp, red color of fruit linings, and concentrations of sugar reduced or in lower frequency. The continued survival and reproduction of the Tobago tree populations, despite different dispersal than on Trinidad, is attributed to their protective adaptations and the different habitats on the two islands. This study suggests that under strong isolation, adaptation to a new consumer situation may be selected for rapidly in certain tropical fruiting trees. THE INTERRELATION BETWEEN FRUITING PLANTS and seed consumers (dispersers and predators) has received much attention in the past 20 years. However, little or no evidence has been provided concerning a fruiting species' ability to ecologically adapt to a different set of consumers (Smith 1970, 1975; Janzen 1983). Although some fruiting species have been shown to be dependent upon a relatively small group of dispersers (Snow 1970; Crome 1975; McKey 1975; Howe 1977, 1983; Greenberg 1981; Wheelwright 1983), growing evidence suggests that specialized seed dispersal systems are relatively rare (Howe & Vande Kerckhove 1979, Howe 1980, Wheelwright & Orians 1982, Schemske 1983, Fleming et al. 1985). Given the likelihood of geographic and temporal variation in types and densities of dispersers available to a fruiting species (e.g., Howe 1977, 1980; Howe & Vande Kerckhove 1979), it is probable that many fruits have maintained a generalized attractiveness useful under many situations of disperser availability. Just as fruits have developed general traits for attracting dispersers, they also have developed various general traits for protection from predation (Janzen 1971, 1983). Each endozoochorous fruit has had to develop means of both attracting dispersers and preventing predation either by the dispersal agents or by true seed predators. In many cases in the tropics (e.g., Janzen 1970, 1971, 1972; Janzen et al. 1976; Howe et al. 1985), seed predators account for the destruction of a large proportion of the seeds produced. In some cases (e.g., Howe et al. 1985) seed predators are thought to be so influential that, without effective dispersal, the plant may not reproduce successfully. Thus, the balance between seed dispersal and predation in fruits often appears to be a delicate one. Nevertheless, in various types of isolation, fruit species may face situations where the coterie of dispersers and predators is vastly altered. The long-term survival of a fruiting species in such a setting rests upon its ability to adapt to the new situation. Is it possible for a generalized endozoochorous fruit to adapt to a very different selective regime? How do such traits as seed shadow, demography, spatial distribution, and abundance change when a species' coterie of consumers changes? Recently isolated continental islands can offer some answers to these questions. The small island of Tobago was connected to Trinidad and the South American mainland in the Pleistocene (see Discussion for evidence). It contains a tract of largely undisturbed forest that shares many species with similar extensive forests on the large nearby island of Trinidad. Despite the floristic and vegetational similarities, the avifaunas of the two islands' forests are markedly different, with reduced overall densities of birds as well as lower numbers of species on Tobago (Keeler-Wolf 1982, pers. obs.). Certain ecological guilds of birds are also substantially different between the two islands. This is particularly true in the case of seed predators and fruit eaters (Keeler-Wolf 1982, pers. obs.). My long-term census data indicate that the guild of principally frugivorous passerines comprises 35-43 percent of the total number of individuals in the I Received 3 March 1986, revision accepted 6 October 1986. 2 Present address: 943 Aquarius Way, Oakland, California 9461 1, U.S.A. 38 BIOTROPICA 20(1): 38-48 1988 This content downloaded from 207.46.13.153 on Fri, 05 Aug 2016 06:21:09 UTC All use subject to http://about.jstor.org/terms Trinidad premontane forest avifauna, whereas in Tobago premontane forest it is only 10-11 percent of the avifauna. Conversely, individuals of seed predators are relatively more abundant on Tobago where they represent 11-15 percent of the avifaunal densities; on Trinidad they comprise only 2-4 percent. Three species of trees-Sloanea laurifolia (Benth.) Bentham (Elaeocarpaceae), Richeria olivieri Philcox (Euphorbiaceae), and Myrcia fallax (A. Rich) DC. (Myrtaceae)-occur on both islands and are heavily used by frugivorous and seed-predatory birds. Different sets of consumers eat their fruits and seeds on each island. On Trinidad, the majority of species feeding on the fruits are principally frugivorous passerines. These typically ingest the ripe fruits of each species and either defecate or regurgitate the seeds unharmed. On Tobago, the most frequent consumers of the fruits of these three species are parrots and chachalacas. The former chip or split open unripe fruit and chip up the seed; the latter ingest whole fruit, grinding and partially digesting the seeds in the