Explosive Local Radiation of the Genus Teagueia (Orchidaceae) in the Upper Pastaza Watershed of Ecuador.

Resumen

In the year 2000 the genus Teagueia Luer (Orchidaceae, subtribe Pleurothallidinae) contained only six species, all epiphytic. Recently we have discovered 26 unusual new terrestrial species of Teagueia on four neighboring mountains in the Upper Pastaza Watershed. All 26 species share distinctive floral and vegetative characters not found in the six previously described members of Teagueia, suggesting that all 26 evolved locally from a recent common ancestor. Each of the Teagueia Mountains hosts 7-15 sympatric species of new Teagueia, suggesting that the speciation events, which produced this radiation, may have occurred in sympatric populations. There is little overlap in the Teagueia species hosted by the mountains, though they are separated by only 10-18 km. This is difficult to explain in light of the high dispersal ability of most orchids. Surprisingly, the species appear not to be habitat specialists. In forest above 3100 m, population densities of these new Teagueia are higher than those of any other genera of terrestrial flowering plants. In the paramos of these mountains they are the most common orchids; they reach higher elevations (3650m) than any other pleurothallid orchid except Draconanthes aberrans. While most species occur at high densities, three species are known only from single examples. These species must have population centers on nearby unexplored mountains, suggesting that we are only tapping the surface of this radiation. The existence of such a rich and completely unexpected flora, with such high beta diversity, poses serious challenges for conservation. Keywords: Beta diversity, sympatric speciation, dispersal