High-Elevation Andean Ecosystems the Andes reflected in the distribution of many plant genera in more than one, and often across the three vegetation zones, makes it imperative to take a broad view of the high-elevation habitat The first question that may be asked concerns how many plant species inhabit the entire Andean corridor Arroyo et al (2010) provided a preliminary estimate of 6700 vascular plant species in 870 genera, indicating a very rich highelevation flora This number incorporated all pa´ramo species found in the Andes as per Luteyn’s (1999) pa´ramo list Such high species richness in the high-elevation belt is not surprising given the north–south trending nature of the mountain range associated with a great variety of climates and the hightopological diversity already alluded to These last factors, in addition to providing an outstanding number of environmental niches in the high-elevation belt itself, are associated with a high diversity of subtending lowland vegetation types (cf Arroyo et al., 1983 for the range of vegetation types in the Chilean Andes), ranging from closed tropical and temperate forests through Mediterranean-type scrublands to open steppe grasslands and desert communities, all providing an outstandingly rich source of evolutionary lineages from which the high-elevation flora has been partially recruited Sizable genera in the high-elevation belt include: Adesmia, Astragalus, Baccharis, Calamagrostis, Calceolaria, Carex, Diplostephium, Draba, Elaphoglossum, Espeletia, Festuca, Gentianella, Lupinus, Geranium, Gynoxys, Halenia, Hypericum, Huperzia Lupinus, Miconia, Nototriche, Oxalis, Pentacalia, Poa, Puya, Senecio, Solanum, Valeriana, and Viola Senecio stands out above all other genera with an estimated 300 species occurring in Andean high elevation habitats Senecio is followed distantly by Calceolaria, Table 99 Gentianella, Lupinus, Nototriche, Solanum, and Valeriana By far the largest high elevation plant families globally for the Andes as well as in each of the three high-elevation zones are the Asteraceae and Poaceae Our early effort to estimate the size of the high-elevation flora brought forward the many typical difficulties associated with developing a continental-wide checklist for high Andean habitats – poor habitat information on many plant specimens, information not available in a readily accessible form, numerous synonymy problems In what is an ongoing refinement process some species have been eliminated as better habitat knowledge has come to hand, while others are being added Additional pa´ramo records are also possible In his comprehensive treatment of the Columbian pa´ramos Rangel (2000b) points out that many species are missing from Luteyn’s (1999) pa´ramo list Taking these various factors into consideration, the above estimates can be expected to change in the near future Information on other plant groups thus far is only available for pa´ramo, which houses 465 species of lichens, 544 species of mosses, and 291 species of hepatics (Luteyn, 1999) Numbers for these groups can be expected to grow substantially as information for the puna and southern Andean steppe becomes available Endemism Andean high-elevation habitats, not surprisingly given their youthful age, support no endemic plant families However, at the generic level, 64 genera in 22 families (Table 1) for all Sixty-four plant genera considered to be confined (endemic) to the high-elevation vegetation belt in the South American Andes Apiaceae: Cotopaxia (PA), Laretia (SAS), Perissicoelum (PA), Pozoa (SAS) Asteraceae: Ascidiogyne (PA), Blakiella à (PA), Calopappusà (SAS), Espletia (PA), Floscaldasia (PA), Gamochaetopsisà (SAS), Huarpeaà (PU), Jalcophila (PA-PU), Loricaria (PA-PU), Marticoreniaà (SAS), Misbrookea (PU)Ã, Mniodes (PA-PU), Noveniaà (PA-PU), Oriastrum (PU-SAS), Raouliopsis (PA), Werneria (PA-PU-SAS), Xenophyllum (PA-PU) Brassicaceae: Aschersoniodoxa (PU), Brayopsis (PA-PU), Catadysiaà (PU), Dactylocardamumà (PU), Englerocharis (PU), Eudema (PA-PU-SAS), Paradiodoxaà (PU), Petroraveniaà (PU), Weberbauera (PA-PU-SAS) Cactaceae: Oroya (PU), Yaviaà (PU) Campanulaceae: Lysipomia (PA-PU) Caryophyllaceae: Pycnophyllopsis (PU-SAS), Pycnophyllum (PU-SAS), Reicheellaà (PU) Cyperaceae: Phylloscirpus (PA-PU-SAS), Zameioscirpus (PU-SAS) Ericaceae: Plutarchia (PA) Juncaceae: Distichia (PA-PU), Oxychloăe (PU-SAS), Patosia (PU-SAS) Lamiaceae: Kurzamraà (PU-SAS) Malvaceae: Nototriche (PA-PU-SAS) Melastomataceae: Bucquetia (PA), Castratella (PA) Orchidaceae: Myrosmodes (PA-PU) Plantaginaceae: Bougeriaà (PU), Melosperma (SAS) Poaceae: Anthocloaà (PU), Dielsiochloaà (PU) Portulacaceae: Lenziaà (PU-SAS) Pteridaceae: Nephopterisà (PA) Ranunculaceae: Barneoudia (PU-SAS), Callianthemoidesà (SAS), Laccopetalumà (PA-PU), Oreithalesà (PA-PU) Saxifragaceae: Saxifragellaà (SAS) Scrophulariaceae: Aragoa (PA) Solanaceae: Combrera (SAS) Valerianaceaea: Aretiastrum (PA-PU-SAS), Belonanthus (PA-PU-SAS), Phyllactis (PA-PU), Stangea (PU) a These genera are considered by some authors as part of Valeriana PA, found in pa´ramo sector; PU, found in puna sector; SAS, found in southern Andean steppe sector Ã, Monotypic genus Information for Pa´ramo mainly follows Sklena´ˇr, et al (2011), but eliminating those genera that are only or partially distributed in the Central American pa´ramos; information for puna and southern Andean steppe from Arroyo (unpublished)