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Investigates how Rocky Mountain butterflies, particularly Pieris and Lycaenidae, respond to invasive Brassicaceae hosts through chemical ecology, oviposition behavior, and thermal physiology, with growing attention to how climate change reshapes these plant-insect dynamics.
Butterflies and their host plants have long served as a window into how species interact, adapt, and evolve in mountain landscapes. In the Gunnison Basin, where short summers, steep elevational gradients, and patchy meadows define the landscape, the relationships between butterflies like Mormon fritillaries (Speyeria mormonia), sulphurs (Colias), and whites (Pieris) and the plants they depend on offer some of the clearest examples of how climate, chemistry, and behavior shape mountain biodiversity. These interactions matter for the basin because butterflies are sensitive indicators of environmental change, important pollinators, and key herbivores whose populations rise and fall with shifts in temperature, snowmelt, and vegetation.
Several concepts are essential for reading the findings that follow. Thermal performance refers to how an insect's body temperature determines its ability to feed, fly, and reproduce — critical in a place where a butterfly's flight muscles only function within a narrow temperature window. A thermal performance curve summarizes this relationship, with peaks at optimal temperatures and declines toward heat or cold extremes. Wing coloration, the pigments and scale structures on butterfly wings, affects both how butterflies warm themselves in cold air and how they signal to mates. Oviposition host plant choice is the decision a female makes about where to lay her eggs, a decision that determines whether her caterpillars survive. When introduced plants chemically resemble native hosts, females may lay eggs on plants that kill their larvae — an evolutionary trap. Heritability — the share of trait variation passed from parents to offspring — determines whether a population can evolve out of such a trap.
Finally, landscape concepts shape outcomes at the population level. Matrix resistance describes how the non-meadow habitat between butterfly populations (forest, willow thickets, roads) either blocks or permits movement. Larval food stress — nutritional shortage during the caterpillar stage — leaves lasting marks on adult body size, flight ability, and egg production. Together these concepts link an individual caterpillar's chewing of a leaf to the long-term persistence of butterfly populations across the Gunnison Basin.
The research area was shaped in the 1960s and 1970s by foundational studies on hybrid zones (Remington, 1968), checkerspot population biology (Ehrlich et al., 1975), and the chemical ecology of pierid butterflies and their mustard host plants . Ward Watt's work on the enzyme phosphoglucose isomerase in Colias established that single-locus genetic polymorphisms could be maintained by natural selection acting through thermal physiology, with heterozygotes flying under a broader range of weather conditions than homozygotes . Joel Kingsolver's parallel work on Colias flight and thermoregulation along Colorado's elevational gradient showed that wing absorptivity, body size, and microclimate jointly determine when and whether butterflies can fly, and that high-elevation populations face elevated overheating risk during brief warm windows .
Temperature-dependent physiological and behavioral responses that affect organism fitness and population dynamics
Effects of non-native species on native community members and ecosystem processes
The proportion of phenotypic variation in a trait that is due to genetic variation, estimated using parent-offspring regression methods
The selection of specific plants by female insects for egg-laying that affects larval survival and development
When previously adaptive traits become maladaptive due to rapid environmental change, such that organisms are attracted to resources that reduce their...
The distribution of individuals across different size or age classes within a population
Controlled choice experiments measuring butterfly oviposition preference between plant species using matched plant materials in screen cages. Preferen...
Extraction and quantification of desulfated glucosinolates from plant leaves using high-performance liquid chromatography with diode array and charged...
Mark-release-recapture protocol for tracking individual butterfly movements among meadow patches using unique felt pen markings and systematic site vi...
Systematic vegetation sampling along parallel transects between sites to quantify matrix composition and calculate proportional cover of different veg...
CO2 emission measurement using flow-through respirometry to quantify resting metabolic rate and flight metabolic capacity in individual butterflies. I...
Transplant butterflies between high and low elevation sites to quantify differences in flight initiation timing and thermal sensitivity across elevati...
Assisted migration consists of the introduction of a species to previously inhabited areas or to new suitable regions. Such introductions have been to...
Introductions of novel plant species can disturb the historical resource environment of herbivorous insects, resulting in strong selection to either...
Stressful juvenile developmental conditions can affect performance and fitness later in life. In holometabolous insects such as butterflies, developme...
Gut microbes are believed to play a critical role in most animal life, yet fitness effects and cost benefit-tradeoffs incurred by the host are poorly ...
Movement uses resources that may otherwise be allocated to somatic maintenance or reproduction. How does increased energy expenditure affect resource ...
Data are in microsoft excel .xlsx format. Descriptions of each data type, including units, are in "comments" associated with the headers on each data ...
A second foundational thread came from Carol Boggs's resource allocation framework, which traced how nutrients acquired by larvae and adults are partitioned into survival, flight, and reproduction. Adult diet restriction in Speyeria mormonia reduced fecundity but conserved lifespan, indicating reallocation away from reproduction under stress (Boggs & Ross, 1993), and male-donated nutrients at mating were shown to contribute meaningfully to female egg production (Boggs, 1990). Subsequent syntheses formalized these patterns into a general theory of how resource acquisition and allocation drive life-history evolution (Boggs, 1992) (Boggs, 2009). Ricketts's mark-recapture work in RMBL meadows established that the matrix between meadows is not uniform: conifer forest was 3–12 times more resistant to butterfly movement than willow thicket, fundamentally reshaping how ecologists think about habitat isolation (Ricketts, 2001).
Across decades of work, butterflies in the Gunnison Basin have shown that climate adaptation is multi-layered and often constrained. Colias butterflies adapt to elevation through wing melanization, which is strongly sex-linked and highly heritable (Ellers & Boggs, 2002), but male mate preferences for paler females oppose the climatic advantage of darker wings, slowing adaptive divergence (Ellers & Boggs, 2003). Larval thermal performance curves themselves differ by elevation, with high-elevation populations evolving higher optimal feeding temperatures to exploit short warm windows (Higgins et al., 2014), and feeding rates have shifted in step with rising temperature variability over recent decades (Buckley & Kingsolver, 2014). Yet climate variability among years often swamps the fitness gains from adaptation, limiting how quickly populations can track warming (Kingsolver & Buckley, 2015). A 60-year comparison of museum specimens found that wing length, melanism, and setal length all increased despite warming — a reminder that evolutionary responses can run counter to simple climate predictions (Maclean et al., 2016).
Resource allocation work has demonstrated that larval food stress carries over into adulthood: nutritionally restricted Speyeria mormonia emerge smaller, with reduced flight metabolic capacity, but allocate proportionally more of their reduced body mass to eggs (Niitepold & Boggs, 2022). Adult diet restriction similarly trades reproduction against survival (Boggs & Freeman, 2005). Wing structure interacts with these life-history outcomes in unexpected ways: silvered ventral scales on Speyeria mormonia brighten the dorsal orange patches involved in mate signaling (Chappell et al., 2023), and the silvering polymorphism itself is controlled by the optix gene and shared across Speyeria species through selective sweeps (Livraghi et al., 2025).
The evolutionary trap posed by the introduced mustard Thlaspi arvense has become one of the system's most studied stories. Pieris macdunnoughii females lay roughly 3% of eggs on this lethal non-native host (Davis & Cipollini, 2013), and although larvae feed less readily on it, mortality is high (Davis et al., 2016). Population growth rates drop sharply when patches of native host plants become separated by even modest distances of invaded ground (Keasar et al., 2015). Yet recent genomic work shows that populations co-occurring with T. arvense have begun to show signatures of local adaptation in larval feeding ability, despite high gene flow (Ravikanthachari et al., 2024), and heritable variation in host preference is unmasked when females encounter the novel host (Steward et al., 2022). The invasion also reshapes belowground communities, altering arbuscular mycorrhizal fungal diversity in invaded meadows (Trautwig et al., 2022).
Early work in the 1970s and 1980s established the biochemical and thermal foundations of butterfly adaptation, work through the 1990s and 2000s built out the resource allocation framework, and studies since 2015 have shifted toward genomic and mechanistic approaches. Recent years have brought a chromosome-level genome assembly for Pieris macdunnoughii (Steward et al., 2021), the mapping of the genus-wide Alba polymorphism in Colias to a single ancient locus maintained by introgression and balancing selection (Tunstrom et al., 2023), and the development of antibody tools to probe nutrient-sensing pathways in non-model lepidopterans (Armstrong & Boggs, 2023). Behavioral frontiers are also opening: studies of mud-puddling now identify landscape contrast, temperature, and sunlight as the primary cues butterflies use to locate sodium sources (von Wallmenich, 2025), and decoy experiments are revealing how achromatic wing borders shape male mate choice in Speyeria (Maass, 2022).
A second frontier is the long-term consequence of the Euphydryas gillettii assisted migration experiment begun at RMBL in 1977, which now provides one of the few empirical tests of how an introduced herbivore reshapes its host plant population over decades (Ravikanthachari et al., 2024). Synthesis work is integrating these threads into broader climate frameworks (Boggs, 2024) (Harvey et al., 2023) (Kingsolver et al., 2011), emphasizing that complex life cycles, extreme weather events, and habitat fragmentation jointly determine insect responses to warming.
Several large questions remain. How quickly can populations evolve out of an evolutionary trap when gene flow from unexposed populations dilutes locally adapted alleles, and which life stages — oviposition behavior or larval feeding ability — are the main targets of selection? How will resource allocation patterns established under historical climate hold up as extreme heat, drought, and altered snowmelt timing become routine? Can the genomic architecture of adaptive traits like Alba, optix-based silvering, and PGI variation predict which species will track climate change and which will not? And how do belowground communities, host-plant chemistry, and butterfly behavior interact as invasive plants spread across the subalpine? Answering these will require linking the genomic, physiological, and landscape-scale tools now converging at RMBL.
Armstrong & Boggs (2023). Antibody development to identify components of IIS and mTOR signaling pathways in lepidopteran species. microPublication Biology. →
Boggs (1990). A general model of the role of male-donated nutrients in female insects' reproduction. American Naturalist. →
Boggs (1992). Resource allocation: exploring connections between foraging and life history strategies. Functional Ecology. →
Boggs (2009). Understanding insect life histories and senescence through a resource allocation lens. Functional Ecology. →
Boggs (2024). Changes in insect population dynamics due to climate change. →
Boggs & Freeman (2005). Larval food limitation in butterflies: effects on adult resource allocation and fitness. Oecologia. →
Boggs & Ross (1993). The effect of adult food limitation on life history traits in Speyeria mormonia. Ecology. →
Buckley & Kingsolver (2014). Rapid evolution and population divergence in response to environmental change in Colias butterflies. →
Chappell et al. (2023). Two sides of the same wing: ventral scales enhance dorsal wing color in Speyeria mormonia. Journal of Experimental Biology. →
Chew (1977). Coevolution of pierid butterflies and their cruciferous foodplants. II. Evolution. →
Davis & Cipollini (2013). Fitness costs of butterfly oviposition on a lethal non-native plant. →
Davis et al. (2016). Larval feeding behavior and leaf components that affect the survival of Pieris macdunnoughii on the invasive mustard Thlaspi arvense. →
Ehrlich et al. (1975). Checkerspot butterflies: a historical perspective. Science. →
Ellers & Boggs (2002). The evolution of wing color in Colias butterflies: heritability, sex linkage, and population divergence. →
Ellers & Boggs (2003). The evolution of wing color: male mate choice opposes adaptive wing color divergence in Colias butterflies. →
Harvey et al. (2023). Scientists' warning on climate change and insects. Ecological Monographs. →
Higgins et al. (2014). Geographic differences and microevolutionary changes in thermal sensitivity of butterfly larvae in response to climate. →
Keasar et al. (2015). Fine-Grained Distribution of a Non-Native Resource Can Alter the Population Dynamics of a Native Consumer. →
Kingsolver (1983). Thermoregulation and flight in Colias butterflies. Ecology. →
Kingsolver & Buckley (2015). Climate variability slows evolutionary responses of Colias butterflies to recent climate change. →
Kingsolver & Watt (1983). Thermoregulatory strategies in Colias butterflies. American Naturalist. →
Kingsolver et al. (2011). Complex life cycles and the responses of insects to climate change. Integrative & Comparative Biology. →
Livraghi et al. (2025). Genetic basis of an adaptive polymorphism controlling butterfly silver iridescence. Current Biology. →
Maass (2022). Does an achromatic border alter color discrimination of male Speyeria mormonia butterflies during mate searching? →
Maclean et al. (2016). Historical changes in thermoregulatory traits of alpine butterflies. →
Niitepold & Boggs (2022). Carry-over effects of larval food stress on adult energetics and life history in a nectar-feeding butterfly. Ecological Entomology. →
Ravikanthachari et al. (2024). Impacts of assisted migration: An introduced herbivore has short-term and long-term effects on its native host plant population. Entomologia Experimentalis et Applicata. →
Ravikanthachari et al. (2024). Patterns of genetic variation and local adaptation of a native herbivore to a lethal invasive plant. Molecular Ecology. →
Remington (1968). Suture-zones of hybrid interaction between recently joined biotas. Evolutionary Biology. →
Ricketts (2001). The matrix matters: effective isolation in fragmented landscapes. American Naturalist. →
Steward et al. (2021). The genome of the Margined White butterfly (Pieris macdunnoughii). Genome Biology and Evolution. →
Steward et al. (2022). Novel host unmasks heritable variation in plant preference within an insect population. Evolution. →
Trautwig et al. (2022). Effects of an introduced mustard, Thlaspi arvense, on soil fungal communities in subalpine meadows. Fungal Ecology. →
Tunstrom et al. (2023). Evidence for a single, ancient origin of a genus-wide alternative life history strategy. Science Advances. →
von Wallmenich (2025). Sensory cues and memory in Lepidopteran mud puddling behavior. →
Watt (1977). Adaptation at specific loci. I. Natural selection on phosphoglucose isomerase of Colias butterflies. Genetics. →
Watt (1983). Adaptation at specific loci. II. Demographic and biochemical elements in the maintenance of the Colias PGI polymorphism. Genetics. →
The color patterns and hues on butterfly wings produced by interaction of light with pigments on the wing scales
The relationship between a host organism and its associated microbial community, including costs and benefits to host fitness
The rate of energy expenditure for basic physiological maintenance processes, measured as CO₂ emission rate.
Framework predicting that larger islands have more species at equilibrium since extinction rates decline and colonization rates increase with increase...
The degree to which novel resources resemble historical resources in their chemical or physical cues
The relative difficulty of movement through different types of non-habitat matrix surrounding habitat patches
Temperature dependence of larval feeding rate, characterized by maximum feeding rate, optimal temperature, and thermal sensitivity parameters
Color-based visual contrast as perceived by animal visual systems
Constancy index that distinguishes between complete constancy, random transitions, and complete inconstancy
Genes that show significantly different expression levels between treatment conditions
Study of how organisms obtain and use nutrients and how nutrition affects fitness
Nutritional limitation during larval development that affects adult phenotype
Females should choose nesting sites that best protect them and their offspring from severe or unpredictable weather events, such as extreme temperatur...
Peak metabolic rate and total energy expenditure during forced flight as measures of dispersal ability
The total volume of CO₂ emitted during flight trials, which reflects overall flight performance including endurance.
Genetic variation maintained in populations by natural selection where different alleles are favored under different conditions
Genetic change in a trait if there is heritable variation, selection, and heritability
Measures of early-life performance that may predict later survival and reproductive success
Tools implemented to accurately predict an organism's physiological response to attributes of interest such as water loss and body temperature
Molecular chaperones that help cells cope with protein folding stress under adverse conditions
Daily monitoring of individual female butterflies including artificial feeding with sucrose solution and daily egg collection. Measures lifetime repro...
Multi-generation breeding program with controlled matings to estimate heritability of preference traits using pedigree-based models accounting for ZW ...
Statistical analysis of flower constancy using Bateman's index and modified Cindex with randomization tests to determine whether butterflies exhibit c...
Photography of butterfly landing sites using polarizing lens to measure landscape contrast between landing spots and surrounding areas. Photos analyze...
Daily forced flight protocol involving 3 × 4 minute flight bouts with rest periods, stimulated by gentle brushing, to experimentally increase energy e...
Controlled food deprivation during larval development by reducing feeding frequency to half that of controls, creating 3-4 periods of 24h food absence...
Systematic sampling of soil fungal communities across vegetation disturbance gradients in subalpine meadows using replicated plot design with grid-bas...