Waiting for the snow to melt…
Connects scientific surveys of rare wetland-dependent species — including dragonflies, ciliates, carnivorous plants, and tiger salamanders — with conservation advocacy around iron fens and other sensitive aquatic habitats in the Gunnison Basin and Colorado high country.
Iron fens are among the rarest wetland habitats in the Rocky Mountains. Unlike typical mountain meadows or marshes, an iron fen is a peat-forming wetland fed by groundwater that is rich in dissolved iron and unusually acidic. The iron precipitates out as a rusty orange crust on rocks and sediments, and the acidic, low-nutrient conditions support a distinctive community of mosses, sedges, carnivorous plants, and specialized invertebrates that cannot survive elsewhere. Only a handful of iron fens exist in Colorado, and several occur within the Gunnison Basin and surrounding national forest lands. Because they accumulate peat slowly over thousands of years and depend on a very specific groundwater chemistry, iron fens are essentially irreplaceable on human timescales — once drained, polluted, or trampled, they do not recover.
The biological communities living in iron fens and other rare wetlands of the Gunnison Basin span a remarkable range of scales. They include carnivorous sundew plants (Drosera rotundifolia) growing along fen edges, cottonsedge (Eriophorum angustifolium) tussocks, filamentous purple algae (Zygogonium) that tint the water, midges (Boreochlus, Paroclus), dragonflies and damselflies whose nymphs develop in the standing water, and microscopic flagellates, ciliates, and fungi that ride on the bodies of larger animals. An epibiont is a small organism that lives attached to the surface of a larger host — for example, a single-celled flagellate (Colacium) attached to the shell of a water flea (Daphnia). These hitchhiking relationships are easy to overlook but turn out to matter for how energy and predation flow through pond food webs.
The Gunnison Basin also harbors rare terrestrial species closely tied to specific habitats and elevations. The grasshopper Arphia conspersa, for instance, occurs in distinct color forms on different mesas, and the dragonfly Somatochlora semicircularis breeds in subalpine pools that can dry out in drought years. Understanding why these species persist in some places and disappear from others requires looking at habitat barriers, climate variability, and the slow recovery times that characterize high-elevation systems. For land managers in the Taylor River-Cebolla Ranger District and similar areas, this body of research provides the baseline needed to recognize, monitor, and protect habitats that are easy to damage and impossible to rebuild.
Much of the early research in this neighborhood was carried out by Ruth Willey and colleagues working in and around RMBL from the 1960s through the 1990s. Willey's grasshopper studies established that Arphia conspersa populations on Black Mesa form sharp color clines and narrow hybrid zones, and that these zones are maintained in part by periodic population crashes and habitat barriers . Earlier behavioral work described the visual and acoustical displays of the same species and showed how the Black Canyon of the Gunnison acts as a barrier to gene flow . Parallel work documented adaptive coloration and morphological variation in the same grasshopper system ; .
Dr. Ruth L. Willey, Senior Investigator at Rocky Mountain Biological Laboratory. Rocky Mountain Biological Laboratory, Bureau of Land Management. Sept...
Correspondence. Covers Mount Emmons Iron Bog, Mount Emmons, Crested Butte. Topics: wetland complex, iron fen. Agencies: Colorado Natural Areas Council...
In the wetlands themselves, foundational discoveries included the seasonal symbiosis between Euglena flagellates and damselfly nymphs, in which the green flagellates inhabit the nymphs' hindguts only during winter (Willey et al., 1970), and the drought-resistance strategies of subalpine dragonfly nymphs that allow Somatochlora semicircularis to survive in pools that periodically dry (Willey & Eiler, 1972). Together these studies established that rare mountain wetlands support biological relationships found almost nowhere else.
A central thread running through the wetland work concerns how tiny attached organisms shape the fate of their hosts. Experiments showed that pigmented flagellates (Colacium vesiculosum) growing on the bodies of water fleas and copepods make those hosts more visible and more vulnerable to fish predators, while unpigmented ciliate hitchhikers do not have the same effect (Willey et al., 1990); (Willey & Threlkeld, 1993). Follow-up work demonstrated that these flagellate populations build up on their hosts through a combination of continuous colonization from the water and on-host reproduction, with colonization dominating early in the host's molt cycle and cell division dominating later (Al-Dhaheri & Willey, 1996). Because the host sheds its exoskeleton every few days, these communities exist in a state of constant renewal across ephemeral habitat patches (Threlkeld et al., 1993).
Work on the grasshopper Arphia conspersa produced equally striking results about how rare populations behave over time. On Black Mesa, a steep transition from entirely orange-red individuals to entirely yellow individuals occurs over just two to five miles (Willey, 1971). In 1970, populations above 9,200 feet crashed almost completely, and the following year showed essentially no recovery, with only small numbers of nymphs detected (Willey, 1971). These observations suggest that hybrid zones between color forms are maintained not by smooth ongoing mixing but by repeated local extinctions in marginal habitat.
For the iron fen plant community itself, monitoring of the carnivorous sundew Drosera rotundifolia documented that the species is highly clustered within its fen habitat: most individuals occur along the northeastern shoreline of the fen pond, within ten meters of the water's edge (Drosera rotundifolia monitoring protocol, 2001). This kind of fine-scale concentration means that even small physical disturbances near the shoreline could remove a large fraction of the local population.
The publication timeline for this area is unusual: most of the foundational papers were produced before 1990, with a smaller burst in the 1990s and only sporadic outputs since 2000. The most recent contribution in this collection is the 2001 Drosera rotundifolia monitoring protocol (Drosera rotundifolia monitoring protocol, 2001), which marks a shift from descriptive ecology toward repeatable, long-term monitoring designed for land managers. The research front is therefore as much about applied conservation — protocols, baselines, and protection of specific fen sites — as it is about new biological discoveries. Methods established earlier, such as systematic walking surveys to count and score grasshoppers by wing color, remain useful templates for tracking rare species across years.
Looking forward, the natural direction for this work is to revisit the historical sites and species with modern tools. Climate change, altered snowmelt timing, and increased recreational pressure in the Gunnison Basin all raise questions that the earlier studies could not address but that their baselines make answerable.
Several important questions remain open. How are iron fens responding to warming temperatures, changes in groundwater inputs, and possible shifts in acidity, and can their slow peat accumulation keep pace with disturbance? Have the high-elevation grasshopper populations that crashed in 1970 recovered, or have their hybrid zones shifted upslope? Do the seasonal symbioses between damselfly nymphs and Euglena, and the predator-mediated dynamics of pigmented flagellate epibionts, still operate in the same way as fish, salamander, and invertebrate communities change? And practically, how can rare-species monitoring protocols like the one developed for Drosera rotundifolia be extended to the other specialized plants, insects, and microorganisms of iron fens before development, drought, or trampling erodes them? These questions sit at the intersection of long-term ecological monitoring, climate adaptation, and the conservation of habitats that exist almost nowhere else.
Al-Dhaheri, R., Willey, R. (1996). Colonization and reproduction of the epibiotic flagellate Colacium vesiculosum (Euglenophyceae) on Daphnia pulex. Journal of Phycology. →
Drosera rotundifolia monitoring protocol (2001). →
Schennum, W. (1971). Adaptive coloration in the grasshopper Arphia conspersa. →
Schennum, W. (1975). A geographical analysis of quantitative morphological variation in the grasshopper Arphia conspersa. →
Threlkeld, S., Chiavelli, D., Willey, R. (1993). The organization of zooplankton epibiont communities. Trends in Ecology and Evolution. →
Willey, R. (1967). Barriers to gene flow in natural populations of grasshoppers. I. The Black Canyon of the Gunnison River and Arphia conspersa. Psyche. →
Willey, R. (1969). Visual and acoustical social displays by the grasshopper Arphia conspersa (Orthoptera: Acrididae). Psyche. →
Willey, R. (1971). Barriers to gene flow in natural populations of grasshoppers. II. Maintenance of narrow hybrid-zones between morphs of Arphia conspersa on Black Mesa, Colorado. Psyche. →
Willey, R., Bowen, W., Durban, E. (1970). Symbiosis between Euglena and damselfly nymphs is seasonal. Science. →
Willey, R., Bowen, W., Rudzinska, M. (1990). Epibiotic euglenoid flagellates increase the susceptibility of some zooplankton to fish predation. Limnology and Oceanography. →
Willey, R., Eiler, H. (1972). Drought resistance in subalpine nymphs of Somatochlora semicircularis Selys (Odonata: Corduliidae). American Midland Naturalist. →
Willey, R., Threlkeld, S. (1993). Planktivore effects on zooplankton epibiont communities: epibiont pigmentation effects. Limnology and Oceanography. →