I’ve just returned from a wonderful conference on the conservation status of Ecuador’s endemic plants, and the role of botanical gardens in conserving them. It was wonderful to see my colleagues, and to see that some of my former students have turned into good professional scientists. The location of the conference, Yachay, was also inspiring. This is a new university and city being built from scratch in the middle of nowhere, with top faculty and luxurious facilities, all intended to offer free top-level education to the best and brightest Ecuadorian students. Entry will be based only on merit and everyone who enters will receive room and board free as well. After the second year, classes will all be given only in English, forcing all students to become bilingual. It is a dramatic vision; we all hope it works out!
I spoke on the Biogeography and conservation of Ecuador’s endemic orchids, a talk that also should be credited to my friend Lorena Endara who kindly let me use her graphics and research results. Plants that are “endemic to Ecuador” are species that are found exclusively in Ecuador and nowhere else in the world; they are the species most in need of conservation efforts in Ecuador. There are about 4500 species of endemic plants in Ecuador, and 1706 of them (38%) are orchids! The family with the next-highest number of endemic species is Asteraceae, the daisy family, with only 361 endemic species (8% of all endemic species), so the orchids clearly dominate the endemic flora of this country. That’s why we at EcoMinga pay so much attention to them.
In my work I focus on the orchid genera with the highest number of endemic species, especially the genus Lepanthes. There are more than 1000 Lepanthes species in Latin America, including over 300 Ecuadorian species; 240 of those species are endemic to the country. These are miniature orchids with very specific habitat requirements and typically very limited distributions, so they provide a rich “language” for making fine distinctions between cloud forests that, to a casual observer, might appear identical.
Hunting these tiny inconspicuous epiphytes in the forest is an adventure in sensory immersion. Botanists normally don’t collect plants that are not in flower, but the flowers of Lepanthes are mostly hidden under the leaves, so botanists unfamiliar with the genus don’t pay attention to them. The famous Scottish botanist Richard Spruce, who lived for six months in my town in 1857 and discovered many of the flowers, ferns, mosses, and liverworts of this area, never noticed even a single one of the more than a hundred species of Lepanthes that live here.
No one understood the flowers of Lepanthes until just ten years ago, when Mario Blanco and Gabriel Barboza discovered that a Costa Rican species was imitating the sexual organs and the pheromones of a female fungus gnat, luring male gnats to mate with the flower! It appears that each species of Lepanthes is pollinated by a single species of fungus gnat. Here and here are more erotic photos of fungus gnats having sex with Lepanthes flowers, taken by my friend Sebastian Vieira in Colombia. This discovery explains the unusual anatomy of most Lepanthes flowers, especially the “appendix”, a complex species-specific organ that taxonomists had often used to distinguish the species. It apparently mimics the female genitalia of a specific fungus gnat.
Since Lepanthes flowers are so often invisible, botanists need a strong search image for their vaguely-distinctive leaves, and especially their thin stems covered with characteristic trumpet-shaped sheaths. Picking these out from the clutter of moss and other epiphytes requires an almost zen-like diffuse concentration, an openness to an odd shape in the periphery of vision, a peculiar non-verbal reliance on subconscious image processing that takes years to develop. The excitement of the hunt comes from knowing that so many species are new to science—every time I turn over an unfamiliar Lepanthes leaf to look at the flower, a little adrenaline rush splashes through my body. But even the now-familiar species are a treat to find, for the beauty of their weird colors and shapes, but also for the interesting biogeographical relationships they reveal about the forests where I find them.
These are orchids that absolutely require misty wet forests that don’t experience long dry periods. The best Lepanthes habitats are bathed many times each day by mist, but are also exposed to lots of air movement and light. They are often nearly absent on the lower slopes of a mountain, but become common and diverse above the well-defined elevation at which clouds form on, or collide with, the mountain’s slope. The zone of Lepanthes richness and diversity often also has an upper limit, where solar insolation on clear days dries out the forest too much for them.
The Lepanthes-rich elevations differ from mountain to mountain. In the upper Rio Pastaza watershed, my area, the winds generally come from the Amazon basin to the east. As you might expect, they carry immense amounts of water vapor. When these wet winds brush up against the Cordillera Abitagua, the first line of mountains facing the Amazon, the water condenses and forms a cloud layer beginning at about 1700m-1800m. Lepanthes, Neooreophilus, and many other orchid genera suddenly become abundant and diverse above that elevation level. There are more than 34 species of Lepanthes on that front range!
Just twenty kilometers to the west lies the next major range of mountains. On that range the Lepanthes start in earnest at about 2200m. Maybe the Cordillera Abitagua clips the cloud layer below that elevation. This second mountain range has more than 28 species of Lepanthes, but less than 1/3 of them are shared with the Cordillera Abitagua! The farther west we go in this watershed, the farther we get from the Amazon basin, the drier it gets. Even though the forest in this second range is very mossy and wet, it is slightly less so than the Cordillera Abitagua, and these hyper-diverse orchid genera appear to be sensitive to these small differences in moisture.
It makes sense that moisture-loving epiphytic orchids, exposed to the wind and without any connection to the soil, would be more sensitive to moisture gradients than terrestrial herbaceous plants and trees. Epiphytes would also be more sensitive to subtle variations in the frequency of mist and rain, even if the total amount of water were the same. Soil stores water and averages out those variations. To a tree rooted in soil, it makes no difference whether it rains 1.0 cm once a week, or 0.5 cm twice a week. But it makes a great deal of difference to a delicate plant with little water-storage capacity, whose roots are exposed to the air. The mean and maximum number of consecutive mist-less days are probably key parameters controlling the distributions of such orchids. Judging from the very restricted distributions of many Lepanthes species, it seems they specialize in particular fog/wind/rain regimes, perhaps more than any other flowering plants.
For many plants this extreme degree of specialization on unique microclimates might be a fatal evolutionary dead-end, as climates change and move around over geological time. Plants that are poor dispersers would get trapped by climate change and become extint if their preferred climate moved from one mountain range to the next. Orchids, though, have the smallest seeds of any flowering plant, naked embryos surrounded by a little cellular net. These seeds are blown long distances by the wind, so a species can explore large areas for suitable habitat. I think this dispersal ability is one of the key reasons why orchids, more than any other plants, can evolve hyper-specialization without becoming extinct.
In a few days, Part 2 will discuss the distributions of Lepanthes and other endemic orchids in our upper Rio Pastaza watershed, and how these distribution patterns can (mostly) be understood in terms of specialization on specific microclimates. It also turns out that the most locally endemic species are concentrated in very specific areas with unique microclimates; finding these areas is the key to protecting the endemic species from extinction. Unfortunately we are shockingly ignorant about the country-wide distributions of endemic orchids, as I will demonstrate with some surprising examples.