A parsimony analysis of endemism (PAE) was performed using the dataset of endemic orchids of Ecuador. The aim of this analysis is to explore the floristic similarity within different vegetation units of continental Ecuador and to identify units in which the orchid richness is concentrated (expressed in branch-length, units with long branches have more species).
* PAE of the orchids of Ecuador was conducted using the geographical operation units described in the Classification System of Vegetation of Continental Ecuador(Sierra et al. 1999). The values over the branches represent the number of endemic orchids, while the values underneath represent bootstrap support above 70% * Label data from herbarium specimens were used for this analysis.
Our results suggest the following patterns:
Coastal region– The different operational units of the coast of Ecuador appear in the top of the figure. The analysis recovers two clades, north-central coast (costa norte-centro) and southern coast clade (costa sur). Within these two clades the evergreen montane forests are the most diverse. The isolated clade of the southern coast (costa sur), represents a dry region with a radically different floristic composition than the northern-central coast, for this reason, it is unique for conservation strategies. The coast has the highest deforestation rate in Ecuador and its ecosystems are the most threatened (Sierra et al. 2002).
Sierra (Andean) region – The resulting clades show interesting patterns. The western and eastern Andes (cordillera) have an almost identical number of species. Nevertheless, the floristic similarity among cordilleras is very low. It is evident that the composition of the orchid flora varies greatly among the northern and southern region of Ecuador. What is even more interesting is that the diversity in north-western cordillera is higher (383 spp.) than the one in the north-eastern cordillera (270 spp.), but this pattern shifts in the south where the eastern cordillera is richer (347 spp.) than the western cordillera (134 spp.). These differences can be attributed to the different evolutionary history of the Andes, to the natural barrier that the Andes represent for dispersion events, and also to the different biogeographical regions that they occupy along their range. The cloud forests of western Ecuador are scarcely represented in the National System of Protected Areas (SNAP). A large proportion of the vegetation has already been converted (Sierra et al. 2002), it is, therefore, important to focus conservation efforts in this region.
Amazon region – In the Amazon, 310 out of 315 are grouped in the Amazon clade, and the majority of the species is concentrated low montane forest (montano bajo) and evergreen montane forest (siempreverde montano bajo), the latter is the most diverse. This clade congregates the forests of the northern and southern Amazon, but it evident the difference between the orchid flora of the lower forests of the north and south.
Far from perfect, this analysis is the first step towards a better understanding the patterns of endemism and orchid diversity in Ecuador and the Andes.
References
Sierra, R., Cerón, C., Palacios W., Valencia, R. 1999. Propuesta preliminar de un sistema de clasificación de la vegetación para el Ecuador continental. Proyecto INEFAN/GEF-BIRF, Wildlife Conservation Society and EcoCiencia. Quito, Ecuador.
Sierra, R., Campos, F., Chamberlin J. 2002. Assessing biodiversity conservation priorities: ecosystem risk and representativeness in continental Ecuador. Journal of Biogeography (59): 95-110.