Manual de Plantas de Costa Rica 97 
Our field work has demonstrated that certain regions have floras that we would not 
have expected based on their classification in the Holdridge system. Very likely this is 
due to the scanty meteorological data available at the time (Herrera, 1985), such data 
being of fundamental importance to the application of the system. Likewise, seasonal- 
ity, a parameter not considered by the Holdridge system, has a very important influence 
on floristic composition (B. Boyle, pers. comm.). This point had also been made by 
Herrera (1985), who indicated that any particular life zone will have heterogeneous cli- 
matic characteristics according to the number of dry months across its geographical ex- 
tremes, thereby affecting the vegetational cover. Haber (2000a) also mentioned that, in 
the region of Monteverde, seasonality has an important influence within any particular 
life zone according to how the site is exposed to the prevailing northerly winds. More 
careful and detailed studies of the effects of seasonality are needed, but the consensus 
is that it has a significant effect on plant diversity. 
An analysis of the specimen database at INBio demonstrates that three of the four 
most diverse conservation areas in the country (see map on back endpapers) lie on the 
seasonal Pacific slope (see Table 2, with abbreviations according to map). Even taking 
into consideration the differences in size and intensity of collecting in these areas, these 
results indicate that seasonality has an effect on species diversity, given that the Pacific 
slope has greater climatic diversity than the wet and relatively uniform Caribbean slope. 
Another analysis of these same specimens according to elevation (O—800 m) also 
shows that floristic diversity may be higher on the Pacific slope than on the Caribbean 
(see the section Analysis at the end of this chapter). If true, it is probably due to the 
greater heterogeneity of seasonality (hence habitat types) of the Pacific slope, where 
the dry season varies from one or two to five or six months. Nevertheless, Haber 
(2000a) found that in the Monteverde region the Caribbean slope is significantly more 
diverse than the Pacific within the 700—1200 m elevational band. Obviously, when di- 
versity is studied on such a relatively small scale (where habitat differences are mini- 
mized), the wetter (Caribbean) side will be found to be more diverse. Elevation also in- 
fluences local climate; one could almost say that climate varies with elevation. 
The following paragraphs will concentrate mostly on floristic descriptions of veg- 
etation patterns (by way of dominant and/or indicator species) that follow from many 
years of field work. By relating these patterns to climatic data, we attempt to charac- 
terize (by species lists) what we call botanical or floristic regions (see map on front 
endpapers) and to discuss how these are related to the Holdridge life zones mapped by 
Tosi (1969) or the “biotic units” of Herrera & Gémez P. (1993). On the other hand, we 
agree with Dressler (1993), who said that any attempt to map and characterize vegeta- 
tion types will be frustrating, if not erroneous, especially in the tropics. 
Floristic components are increasingly used to characterize the diversity and bio- 
geographic relations among forests of the world, because these are the elements that 
best reflect the results of biotic and abiotic interactions at any particular site. Our field 
work suggests that species listed in the following pages can also serve as indicators, 
