Manual de Plantas de Costa Rica 99 
their occurrence at a particular site being more or less predictive of the diversity of the 
area. It is assumed that the region where such indicators are most common is the source 
of their dispersal to other regions. The botanical or floristic regions we propose corre- 
spond closely to the major geographic features (such as slopes, mountain ranges, plains, 
and valleys) indicated on topographic maps; their boundaries, determined generally by 
elevation and rivers, could certainly be refined by more field work (see also the chapter 
on The physical environment). We first discuss the four major mountain ranges (“‘cor- 
dilleras’’) presented, as for the other areas, from northwest to southeast. Subsequently, 
we consider the regions of the Caribbean slope, subdivided into a northernmost zone and 
then a specifically coastal zone, mentioning for each its respective plains. Finally, we 
discuss the Pacific slope, dividing it into plains, valleys, and minor ranges. 
Before beginning with the characterization of these regions, we should first men- 
tion three types of habitat— mangroves, beaches, and islands —that fall outside or tran- 
scend the geographic boundaries of said regions. Mangroves comprise a unique and 
quite homogeneous landscape wherever they are found. It is estimated that mangroves 
cover an area of 41,592 ha in Costa Rica and that they tend to increase in diversity with 
increased precipitation, so that those in the south of the country are the richest floristi- 
cally (Jiménez, 1994). Mangroves are quite common all along the Pacific slope, where 
the core or nuclear vegetation is made up of 
conspicuous species such as the following!: 
Avicennia bicolor, A. germinans, Conocar- 
pus erectus, Laguncularia racemosa, Pel- 
liciera rhizophorae, Mora oleifera, Muellera 
frutescens, Rhizophora mangle, R. race- 
mosa, and Tabebuia palustris. These species 
are widely distributed among mangroves, 
although a few, like Pelliciera rhizophorae 
and Tabebuia palustris, reach their northern 
limit at Playa Potrero Grande (Santa Elena 
Peninsula); Avicennia bicolor occurs only in 
the mangroves of Guanacaste, and Mora 
oleifera only in those to the southeast. Im- 
portant examples of mangroves are found at 
Puerto Soley, Playa Potrero Grande, Tama- 
rindo, the Gulf of Nicoya, Damas-Palo Seco, 
Sierpe-Térraba, Rincén de Osa, Puerto Ji- 
ménez, Golfito, and Coto Colorado. On the Mangrove, Playa Langosta 
Caribbean side, mangroves are found princi- near Tamarindo (2003) 
' See Appendix for family affiliations and authority names for all italicized scientific names mentioned in 
this chapter, and elsewhere in this volume. 
