Checking billy barr’s snow log…
Explores how hybridization, climate change, and ecological niche breadth shape plant and animal population dynamics in Rocky Mountain stream and meadow ecosystems, with a focus on cinquefoil hybrids and riparian territory use.
The high meadows, streamsides, and rocky slopes around the Rocky Mountain Biological Laboratory (RMBL) in the Upper Gunnison Basin host plant and animal communities shaped by a long history of climatic upheaval and by ongoing interactions among closely related species. Research in this neighborhood examines how alpine and subalpine plants — particularly cinquefoils in the genus Potentilla — respond to a warming, drying climate, how hybridization between related species creates new ecological possibilities, and how streamside organisms from plants to dippers respond to changes along mountain waterways. The Gunnison Basin is an unusually good place to ask these questions because its topographic isolation and high elevation have preserved an exceptional fossil and pollen record, allowing researchers to compare today's communities with those of the deep past.
Two concepts are central to understanding the findings that follow. The first is parent-hybrid dynamics: when two related plant species grow near one another and cross-pollinate, they can produce hybrid offspring that carry a mix of traits from both parents. Whether those hybrids thrive, struggle, or outperform their parents depends on environmental conditions. In a warming climate, hybrids can either serve as a bridge to new habitats or, conversely, become demographic dead-ends if they inherit the wrong combination of traits. The second concept is territory size, used here in the specific sense of the linear distance a streamside animal — for example, an American Dipper — defends along a creek. Territory length is a useful measure because it integrates food availability, habitat quality, and competition into a single number that can be tracked from year to year as conditions in the stream change.
Readers should also know that the Gunnison Basin's modern ecosystems are layered on top of a late Pleistocene landscape that looked very different — largely open sagebrush steppe-tundra with coniferous forests confined to the basin edges. Understanding which species persisted, which were lost, and which arrived only recently provides crucial context for interpreting current ecological change.
The earliest foundational studies in this neighborhood reconstructed the deep environmental history of the southern Colorado Rockies. Pollen analysis of varved lake sediments at Devlins Park documented a landscape dominated by Artemisia (sagebrush) and pine during the last major Pinedale glacial advance, with arboreal pollen percentages far lower than today (Legg & Baker, 1980). Vertebrate fossils from Haystack Cave extended this picture, showing that the Gunnison Basin was largely unforested grassland and sagebrush shrubland in the lower basin during the late Pleistocene, with open coniferous forests only at the basin's edges . Early natural-history work on Gunnison County mammals, such as Quick's notes on weasel ecology , established baseline observations of the small carnivore community that still occupies these meadows and streamsides.
To understand parent-hybrid dynamics in cinquefoil (Potentilla) species in the Colorado Rocky Mountains, I am estimating environmental overlap among p...
To understand parent-hybrid dynamics in cinquefoil (Potentilla) species in the Colorado Rocky Mountains, I am estimating environmental overlap among p...
To understand parent-hybrid dynamics in cinquefoil (Potentilla) species in the Colorado Rocky Mountains, I am estimating environmental overlap among p...
To understand parent-hybrid dynamics in cinquefoil (Potentilla) species in the Colorado Rocky Mountains, I am estimating environmental overlap among p...
Landmark plant-ecology studies from the late twentieth century examined how Potentilla species interact with their neighbors and herbivores. Vail's work on Potentilla gracilis explored how plant density mediates interactions with animals (Vail, 1983), and Hackney's study of magnesium chloride road dust documented an early concern about human disturbance to RMBL's local flora (Hackney, 1999). Together, these studies set up the central questions — how do alpine plants and their communities respond to change, whether climatic, biotic, or anthropogenic? — that more recent work continues to address.
The most thoroughly documented findings in this neighborhood concern hybridizing cinquefoils in the Southern Rockies. Across thirteen natural populations of Potentilla hippiana, P. pulcherrima, and their hybrid, all three taxa had lower predicted population growth rates under warm, dry conditions, indicating broad climate vulnerability (Carscadden et al., 2023). However, the parents responded very differently: P. hippiana maintained positive growth rates across a broader range of conditions, while P. pulcherrima populations declined as conditions became warmer and drier (Carscadden et al., 2023). Hybrids consistently had lower predicted growth rates than P. hippiana, and they also showed significantly lower performance for growth, flowering probability, and flower production across multiple sites (Carscadden et al., 2023). Year-to-year variation was also pronounced, with population growth rates differing significantly between 2018–2019 and 2019–2020 (Carscadden et al., 2023). These results suggest that, in this system, hybridization does not appear to be producing offspring better suited to a hotter, drier future than at least one of their parents.
A conceptual contribution from the same research program clarified how ecologists should measure a species' tolerance range. Niche breadth operates hierarchically — from within individuals up to among populations — and each level contributes to overall species-level patterns (Carscadden, 2021). Importantly, simple presence/absence data tend to yield larger niche-breadth estimates than dynamic measures like population growth rates, because they cannot distinguish a shrinking population from a stable one (Carscadden, 2021). This matters for predicting which alpine species are truly secure under climate change versus those that merely appear secure on a distribution map.
Paleoecological findings reveal both vulnerability and resilience over deep time. Excavations of Haystack, Cement Creek, and Signature Caves show that at least five extinct large mammals disappeared from the Upper Gunnison Basin by the Early Holocene, along with one extinct small mammal, while four additional small mammals were extirpated as forests expanded upslope and open habitats shrank (Emslie & Meltzer, 2019). Despite these losses, taxonomic richness and evenness at Cement Creek Cave indicate that the small-mammal community as a whole showed high resilience across more than 40,000 years of major climate shifts (Emslie & Meltzer, 2019).
Early work in this neighborhood, from the 1950s through the 1980s, established the pollen, vertebrate, and natural-history baselines for the Gunnison Basin. Studies in the 2010s and 2020s have shifted decisively toward quantitative demography and climate response. The most recent paleoecological synthesis used the Upper Gunnison cave record to ask explicitly how small-mammal communities have weathered past climate change (Emslie & Meltzer, 2019), while contemporary plant studies have moved from descriptive accounts to multi-year, multi-site demographic models of hybridizing populations (Carscadden et al., 2023). Conceptual work on niche breadth is pushing the field to use dynamic measures — actual population growth — rather than static range maps when forecasting species' futures (Carscadden, 2021).
Streamside research is an emerging but still preliminary frontier. Work on American Dippers and the nuisance diatom Didymosphenia germinata has begun to ask how changes in stream productivity affect the linear distances dippers defend, though early sampling has been limited (Baker, 2017). Other recent contributions situate Gunnison Basin ecology within broader high-elevation human and environmental history (Andrews et al., 2021); (Meltzer & Eren, 2021); (Morgan et al., 2021).
Several major questions remain. First, under what conditions, if any, do Potentilla hybrids outperform their parents — and could hybrid zones shift uphill faster than parental species as the climate warms? Second, how should we reconcile the deep-time resilience of small-mammal communities with the apparent vulnerability of modern alpine plants, and what does that tell us about which taxa will be the most sensitive indicators of change in the coming decades? Third, streamside systems — including dipper territories, riparian Potentilla populations, and the algae and invertebrates that link them — need much more sampling before we can say how dust deposition, invasive diatoms, and altered flow regimes are reshaping them. Addressing these questions will require sustained, multi-year demographic monitoring paired with the kind of paleoecological perspective that RMBL and the Gunnison Basin are uniquely positioned to provide.
Andrews, et al. (2021). The Environmental Context. University Press of Colorado eBooks. →
Baker (2017). Effects of Didymosphenia germinata on American Dipper (Cinclus mexicanus) Territory Size. →
Carscadden (2021). On the structure and significance of ecological niche breadth. →
Carscadden, et al. (2023). Demographic responses of hybridizing cinquefoils to changing climate in the Colorado Rocky Mountains. Ecology and Evolution. →
Emslie (1986). Late Pleistocene vertebrates from Gunnison County, Colorado. Journal of Paleontology. →
Emslie, Meltzer (2019). Late Quaternary vertebrates from the Upper Gunnison Basin, Colorado, and small-mammal community resilience to climate change since the last glacial maximum. Quaternary Research. →
Hackney (1999). The Effects of Road Dust with Magnesium Chloride on the local Flora of the Rocky Mountain Biological Laboratory, Gothic, Colorado. →
Legg, Baker (1980). Palynology of Pinedale Sediments, Devlins Park, Boulder County, Colorado. Arctic and Alpine Research. →
Meltzer, Eren (2021). The Mountaineer Folsom Projectile Point Assemblage. University Press of Colorado eBooks. →
Morgan, et al. (2021). Block C. University Press of Colorado eBooks. →
Quick (1951). Notes on the Ecology of Weasels in Gunnison County, Colorado. Journal of Mammalogy. →
Vail (1983). Density effects in the plant-animal interactions of Potentilla gracilis douglas (Roseaceae). →