Biogeography of the Pastaza Watershed


Zone A: Foothill outer slopes (1000-1700 m)

Zone A includes the easternmost slopes of the first foothills facing Amazonia, up to about 1700 m. Above 1700 m the species composition abruptly changes.



     These are the first significant elevations facing Amazonia, and they are very wet. The forest is tall and dense, and the trees carry a very heavy load of epiphytes. The diversity of this tall forest is high, and there are a very large number of plant species that appear to be endemic to the zone. Many of the endemic orchid species were discovered by Joe Brenner, a plant lover who lived in nearby Puyo. Additional species were discovered by Dr. Calaway Dodson, who did a study of a 10 sq. km section of this forest north of Mera. Dr. Dodson found 203 species of orchids in that forest, an extremely high number relative to other comparable Ecuadorian sites. I have spent only a small amount of time exploring this area, alone and with botanists Stig Dalstrom, Tom Croat, and John Clark. Nevertheless in that short time we discovered several new orchid species, and even what appears to be a new genus. See the following pages for photos.

    The flora of this zone is closely related to the flora of my Zone C, the Rio Topo/Rio Negro valleys, which has similar elevations. It is also related to the flora of other low eastern foothills facing Amazonia, such as the Cordillera Galeras north of the Rio Napo. Some of the orchids that were originally thought to be endemic to Zone A turned up in the Galeras mountains when I did a survey there.

   The most spectacular endemic orchids of this zone are undoubtedly the new Masdevallia species that Stig Dalstrom and I discovered here over the last two years. Dr Luer is just now publishing the descriptions of the first two we found, Masdevallia stigii and Masdevallia loui. I have several other possibly new Masdevallia species from here in cultivation, but they have not flowered yet. Other new species from Zone A include a strange Stellilabium I just discovered, which mimics a fly butt and is pollinated by a male fly as it tries to mate with the flower.

      I hope I will eventually be able to include pages on all seventeen unique Pastaza Watershed endemic orchids that are found in Zone A. These orchids grow nowhere else in the world. Unfortunately these species are very rare and hard to find, and many have only been found once. At the moment I have found about half of them. I also include a few orchids which are almost endemic to this zone; they have very small ranges special non-orchids which grow in my Zone A and which have not been found anywhere else in the world, and a few orchids that are endem. The total number of Upper Pastaza Watershed strict endemics found in this zone is 68, more than in any other zone of the Watershed. Unfortunately this zone is almost completely unprotected, and very vulnerable to deforestation.


Species illustrated in this chapter:

( Each opens in its own browser window; close it and you will be back on this page.)


Plants known only from the Upper Pastaza Watershed:

New genus

Coryanthes bergoldii

Epistephium lobulosum

Kefersteinia lindneri

Kefersteinia minutiflora

Lepanthes hispidosa

Lepanthes ruthiana

Lepanthes "Selby"

Masdevallia stigii

Masdevallia loui

Masdevallia mentosa

Maxillaria merana

Monopyle paniculata (Gesneriad)

Myoxanthus ephelis

Orleanesia ecuadorana

Rare species known only from this zone and immediately adjacent provinces:

Chondrorhyncha merana

Lepanthes ornithocephalus

Porroglossum condylosepalum

Stellilabium jostii

Click here for a table of the Pastaza Watershed endemics known from Zone A.


To pick another Pastaza Watershed zone to explore:

Close this browser window and choose another zone from the contents page, or press "Forward" below to move to the next zone.



Biogeography of the Pastaza Watershed