Integrates long-term demographic monitoring, integral projection models, and pollination ecology to understand how climate variability — including lagged and dormant-season effects — shapes population vital rates in alpine plants and insect communities.
Alpine and subalpine ecosystems in the Gunnison Basin are among the most sensitive landscapes on Earth to climate change. The plants and pollinators that define these meadows must complete their life cycles within short, snowmelt-bound growing seasons, and even small shifts in temperature, precipitation, or snowmelt timing can ripple through every stage of their development. Researchers working out of the Rocky Mountain Biological Laboratory (RMBL) have used decades of long-term observation to track how individual plants survive, grow, flower, and reproduce, and how the insects that pollinate them respond to a warming world. Understanding these dynamics matters not only for biodiversity but for the basin's broader ecological integrity, including watershed function, wildflower tourism, and the maintenance of native pollinator communities.
A few key ideas underpin the findings that follow. Vital rates are the demographic building blocks of a population: the probability that an individual survives a year, grows, flowers, produces seed, or germinates. Tracking how climate affects each of these rates across a plant's life cycle reveals how populations expand, contract, or shift in space. In species with separate male and female individuals, the operational sex ratio (the proportion of flowering individuals that are male) shapes mating opportunities; when males and females respond differently to climate, a sex-specific climate response can tilt this ratio and create mate limitation. Some long-lived plants, such as the showy green gentian Frasera speciosa, follow a monocarpic perennial life history, accumulating resources for decades and flowering just once before dying.
Methodologically, this research depends on linking weather records to demographic data over many years. A sliding-window analysis tests many possible time windows during which climate might influence a vital rate, rather than assuming the growing season matters most. Insect biomass, measured from standardized trap catches, serves as a proxy for pollinator abundance. Together, these concepts let researchers ask not just whether climate change is affecting alpine populations, but exactly how, when, and through which life-cycle bottlenecks.
The foundations of pollination research at RMBL were built on the recognition that alpine and montane systems are unusual in being dominated by flies rather than bees. Inouye and Pyke (Inouye & Pyke, 1988) compared the pollination biology of Australia's Snowy Mountains with montane Colorado and documented the overwhelming prevalence of Diptera as flower visitors, a pattern Kearns confirmed across an elevational gradient on Colorado's western slope, where flies came to dominate flower visitation as other insect orders dropped out at high elevations. Kearns and Inouye synthesized these insights into a broader conservation framework, drawing attention to how poorly understood many pollination linkages were, and Kearns extended the argument by highlighting the unrecognized conservation status of fly pollinators in North America. A trilogy of reviews (; ; ) consolidated current knowledge of fly diversity, floral rewards, and foraging ecology.
Demographic rates including survival, growth, flowering probability, seed production, and germination that determine population dynamics
Population parameter measuring the relative frequency of males and females, specifically operational sex ratio of flowering individuals
When populations have not yet adapted to current environmental conditions due to time delays
Proportion of flowering individuals that are primarily male-expressing
Beetles were captured using speed nets, marked with tungsten needle dot codes on elytra, and released for recapture monitoring to estimate population ...
Meta-analytical approach to synthesize population-level climate sensitivities across multiple species using structured population models and standardi...
Size-structured population model that incorporates climate effects on vital rates to project population dynamics and calculate population growth rates...
Long-term systematic collection of first sighting and median activity dates for plants, insects, mammals, amphibians and birds in a high-elevation mon...
Measurement of water-use efficiency differences between plant sexes using leaf carbon isotope ratios (δ13C) to understand mechanistic basis of sex-spe...
Uses centimeter-precision GPS to map exact locations of all individuals in study plots, enabling calculation of population density and neighbor relati...
Water report (1993). Covers Arkansas River Valley, Arkansas River, Adobe Reservoir. Topics: water transfer alternatives, water banking, return flow an...
Joanne Williams. September 11, 2005.
1. Despite a global footprint of shifts in flowering phenology in response to climate change, the reproductive consequences of these shifts are poorly...
Males and females are ecologically distinct in many species, but whether responses to climate change are sex-specific is unknown. We document sex-spec...
Meta-analysis of montane plant species range shifts in response to climate change.
This file contains the data and R scripts to: 1. fit vital rate models, 2. build population projection models, and 3. run stochastic simulations. The ...
Rates of elevation range shift in montane plants due to climate change collected from the literature. See README.txt for column descriptions.
Analysis of sex differences in Valeriana edulis life expectancy upon reaching sexual maturity and population operational sex ratios.
In parallel, demographic and reproductive studies established how plant mating systems and life histories shape alpine populations. Bierzychudek (Bierzychudek, 1985) examined patterns in plant parthenogenesis, and Bierzychudek (Bierzychudek, 1987) showed that pollinators can actually raise the cost of sex by avoiding female flowers. Bierzychudek and Eckhart (Bierzychudek & Eckhart, 1988) laid out the conceptual framework for spatial segregation of the sexes in dioecious plants, anticipating later work on how males and females respond differently to environmental gradients.
A central thread of recent RMBL research is that climate change is reshaping populations through subtle, sex- and stage-specific pathways. In the dioecious subalpine herb Valeriana edulis, Petry et al. (Petry et al., 2016) showed that males are more water-use efficient than females and that operational sex ratios have become increasingly male-biased at higher elevations, with male frequency climbing at roughly 175 meters per decade, far faster than typical species range shifts. This sex-specific climate response has reduced female reproductive success and demonstrates that climate can drive population change without altering where a species occurs. A complementary pattern appears in gynodioecious Geranium richardsonii, where the proportion of female plants declines significantly with elevation (Davis et al., 2016).
Work on demography has revealed that climate's fingerprints are often hidden outside the growing season. Compagnoni et al. (Compagnoni et al., 2016) showed that temporal correlations between vital rates can substantially amplify or dampen year-to-year variability in long-lived perennials. Evers et al. (Evers et al., 2021) extended this insight by demonstrating that, for many vital rates, the most predictive climate windows lie in the dormant season or lag one to four years behind the response, a pattern almost universally overlooked in the published literature. Experimental snow removal in Helianthella quinquenervis (Iler et al., 2014) confirmed that early snowmelt directly imposes water stress on alpine forbs.
Climate effects also propagate through pollinator and herbivore communities. Syrphid flies are more abundant at higher elevations, tracking the greater density and diversity of flowers there (Iler et al., 2012), and during drought years pollinators contract rather than broaden their floral niches (McCabe et al., 2019). Grasshopper abundance declines with elevation, yet high-elevation plants suffer almost twice the herbivore damage of low-elevation plants in feeding trials (Klens & Mooney, 2021), indicating that elevational gradients in plant defense do not simply mirror gradients in herbivore pressure.
Early work in the 1980s and 1990s described who pollinates what and established the dioecious life histories of alpine plants. Studies in the 2010s linked long-term demographic data to climate. Since 2020, research has moved toward forecasting, mechanism, and integration of soils, neighbors, and community context. Zeh (Zeh, 2021) built a Demographic Distribution Model for Valeriana edulis driven by snowmelt, growing-season temperature, and precipitation, correctly predicting the majority of population presences and absences and showing that later snowmelt boosts population growth while warmer, wetter summers depress it. Zhang and Peterson (Zhang & Peterson, 2020) showed that climate-informed forecasts of sex ratios outperform both null models and simple linear trend extrapolations in most populations. Davis (Davis, 2023) found that elevation does not systematically predict density-dependent dynamics in Valeriana, and Davis (Davis, 2024) showed that different fitness components depend on neighbors at different spatial scales. Boxwell (Boxwell, 2025) added soil grain size as a major control on survival, flowering, and seed production, while Pham (Pham, 2022) documented surprisingly high rates of male inconstancy in this nominally dioecious species.
Community-level work is also moving forward. Cohen et al. (Cohen et al., 2025) found that even highly divergent species can produce viable pollen tubes in each other's pistils, so heterospecific pollen transfer can cause ovule loss across an alpine community regardless of evolutionary distance. Dunn et al. (Dunn et al., 2023) showed that insect biomass responses to temperature vary strongly among regions of North America, cautioning against one-size-fits-all climate projections, and Dean et al. (Dean et al., 2024) demonstrated that bird predation on insects rises with both elevation and aridity through behavioral rather than density-dependent mechanisms.
Major unknowns remain about how alpine populations will integrate these many simultaneous pressures over coming decades. Can plants adapt fast enough to keep pace with climate-driven shifts in sex ratios, or will adaptation lag drive declines through mate limitation? How do dormant-season and multi-year lagged climate effects interact with soil properties to set range limits for sessile species? Will fly-dominated pollinator communities, so distinctive at high elevations, persist as warming reorganizes insect phenology and regional biomass trajectories? And how do shifts in pollinator niche breadth, heterospecific pollen transfer, and herbivore behavior combine to determine reproductive success at the community scale? Answering these questions will require continued long-term monitoring at RMBL coupled with mechanistic, climate-driven population models linked to soils, neighbors, and pollinator networks.
Bierzychudek, P. (1985). Patterns in plant parthenogenesis. Experientia. →
Bierzychudek, P. (1987). Pollinators increase the cost of sex by avoiding female flowers. Ecology. →
Bierzychudek, P., Eckhart, V. (1988). Spatial segregation of the sexes of dioecious plants. American Naturalist. →
Boxwell, ? (2025). The role of soil in regulating plant performance in Valeriana edulis. →
Cohen, et al. (2025). Phylogeny does not predict the outcome of heterospecific pollen-pistil interactions in a species-rich alpine plant community. American Journal of Botany. →
Compagnoni, A., et al. (2016). The effect of demographic correlations on the stochastic population dynamics of perennial plants. Ecological Monographs. →
Davis, ? (2023). Elevation Does Not Predict Density Dependent Population Dynamics in Valeriana edulis. →
Davis, ? (2024). Variation in interaction zone size and influence of sex on fitness components of Valeriana edulis. →
Davis, et al. (2016). Sex ratio and reproductive success along elevational gradients of gynodioecious populations of Geranium richardsonii. →
Dean, et al. (2024). Decomposing an elevational gradient in predation by insectivorous birds. Ecosphere. →
Dunn, et al. (2023). Extensive regional variation in the phenology of insects and their response to temperature across North America. Ecology. →
Evers, et al. (2021). Lagged and dormant season climate better predict plant vital rates than climate during the growing season. Global Change Biology. →
Iler, et al. (2012). Syrphid fly distributions along an elevation gradient in and around the Rocky Mountain Biological Laboratory. →
Iler, et al. (2014). Experimental examination of early snowmelt-induced water stress in Helianthella quinquenervis. →
Inouye, D. W., Pyke, G. (1988). Pollination biology in the Snowy Mountains of Australia, with comparisons with montane Colorado, USA. Australian Journal of Ecology. →
Inouye, et al. (2015). Flies and Flowers III: Ecology of Foraging and Pollination. Journal of Pollination Ecology. →
Kearns, C. A. (1992). Anthophilous fly distribution across an elevation gradient. American Midland Naturalist. →
Kearns, C. A. (2001). North American dipteran pollinators: assessing their value and conservation status. Conservation Ecology. →
Kearns, C. A., Inouye, D. W. (1997). Pollinators, Flowering Plants, and Conservation Biology. BioScience. →
Klens, ?, Mooney, K. (2021). Tests for Elevational Gradients in Herbivore Abundance and Plant Resistance in the Rocky Mountain Ecosystem. →
Larson, et al. (2001). Flies and flowers: taxonomic diversity of anthophiles and pollinators. Canadian Entomologist. →
McCabe, et al. (2019). Observing pollinator trait variation in relation to niche breadth in seasons of high and low precipitation. →
Petry, et al. (2016). Sex-specific responses to climate change in plants alter population sex ratios and performance. Science. →
Pham, ? (2022). Dynamics of male inconstancy in Valeriana edulis in the abiotic and mating environment. →
Woodcock, et al. (2014). Flies and flowers II: Floral attractants and rewards. Journal of Pollination Ecology. →
Zeh, ? (2021). Nowcasting the distribution of Valeriana edulis using climate driven population models. →
Zhang, ?, Peterson, ? (2020). Assessing the forecastability and forecast skill of models to predict sex ratios of Valeriana edulis. →
Plants that live for multiple years but flower only once before dying
Differential responses between sexes to environmental variation potentially creating imbalance in the frequency of males and females
Statistical approach that tests all possible combinations of climate drivers and temporal windows to identify optimal predictive time scales
The complete sequence of developmental stages from germination through survival, growth, flowering, and reproduction in sessile plants
Total dry weight of insects captured, used as proxy for abundance and population size
Wild ant colonies were collected and split into paired fragments, then maintained on controlled diets (carbohydrate vs protein-rich) to test effects o...
Use existing citizen science bird observation data from eBird database to characterize bird abundance and diversity patterns across environmental grad...
Artificial prey made from green modeling clay are deployed on tree branches to estimate bird attack rates over a standardized time period. Attack mark...
Statistical approach using the climwin package to determine optimal phenological windows of climate variables that best predict biological timing by t...
Calculation of site-specific wetness indices using mean annual precipitation and temperature data to characterize local climate conditions for experim...
Analysis method that reveals demographic and trait mediated processes that buffer population growth using transient life table response experiments.
Measurements of focal females, including proportion of flowers that successfully produced seed. See README.txt for column descriptions.
Snowmelt data used to test for an effect of elevation on snowmelt date. See README.txt for column descriptions.
Analysis of Valeriana edulis sex differences in integrated water use efficiency and population operational sex ratios.
This .zip archive contains a shapefile (including .shp, .shx, .dbf, and .prj components) that describes the locations of focal females used in 2015 in...
GPS coordinates of Valeriana edulis plants in four populations and their sex. See README.txt for column descriptions.
This .zip archive contains a shapefile (including .shp, .shx, .dbf, and .prj components) that describes the locations of focal females used in 2014 in...
Describes all data files and R analysis scripts.
This .zip archive contains a shapefile (including .shp, .shx, .dbf, and .prj components) that describes the locations of all Valeriana edulis plants i...
Annual rates of sex- and size-specific growth and survival from tagged plants at four populations (1978-1981). See README.txt for column descriptions.
Estimation of the mating function – how local operational sex ratio affects female reproductive success – of Valeriana edulis. This script includes a ...
Insectivorous birds have ecologically important effects on prey abundance, behavior, and evolution, and through top-down control birds indirectly redu...
This .zip archive contains a shapefile (including .shp, .shx, .dbf, and .prj components) that describes the boundary of a representative plot of Valer...
Operational sex ratios across the elevation range of Valeriana edulis from 1978 and 2011. See README.txt for column descriptions.
Carbon isotope ratios of Valeriana edulis leaf samples used to test for sex differences in integrated water use efficiency. See README.txt for column ...
Premise: Co-occurring plant species that share generalist pollinators often exchange pollen. This heterospecific pollen transfer (HPT) impacts male an...
Analyses of Valeriana edulis operational sex ratios across the species' elevation range and over time (1978-2011).
The phenology of vegetation, namely leaf-out and senescence, can influence the Earth’s climate over regional spatial scales and long time periods (e.g...
Climate station data from the Rocky Mountain Biological Laboratory to test for effect of elevation on soil moisture. See README.txt for column descrip...
Long-term snowmelt data (1978-2014) collected at one mid-elevation location near the Rocky Mountain Biological Laboratory by billy barr. See README.tx...
Analyses of climate change over elevation and time in the study area.
Data for meta-analysis of montane plant species range shifts in response to climate change.
Phenology - the timing of life events - determines how a species’ life cycle aligns with the abiotic and biotic environment, however, climate change h...
Long-term data sets of population dynamics of plants are scarce, yet provide valuable information for addressing critical ecological and evolutionary ...
The trace element selenium is an essential element with a narrow window between concentrations needed to support life and those that cause toxicity to...
Data on first day of bare ground (snowmelt date, shown as day of year; 1 Jan = 1) from a long-term snow monitoring plot monitored by billy barr, near ...
Understanding the influence of environmental variability on population dynamics is a fundamental goal of ecology. Theory suggests that, for population...
Fragmentation is ubiquitous across tropical forests and drives marked shifts in tree community composition by differentially affecting species’ disper...