The adult demography of a population of Speyeria mormonia (Lepidoptera: Nymphalidae) near Gothic, Colorado USA was studied for four years. Values of demographic parameters, including survival, dispersal and sex ratio, varied yearly, without major changes in density. Shift in sex ratio with constant

Group size effects, whereby animals allocate less time to antipredator vigilance as a function of increasing group sizes are widely reported in many taxa, but group size is but one of many social attributes that could increase a individual’s sense of security. Indeed, meta-analyses suggest that grou

Climate change increasingly drives local population dynamics, shifts geographic distributions, and threatens persistence. Gene flow and rapid adaptation could rescue declining populations yet are seldom integrated into forecasts. We modeled eco-evolutionary dynamics under preindustrial, contemporary

ABSTRACT A nearly complete skull of Eutretauranosuchus delfsi was uncovered at the upper Jurassic Dry Mesa Dinosaur Quarry in the Brushy Basin Member of the Morrison Formation in western Colorado. It permits an expanded description of the taxon. Like the holotype, from Canyon City, Colorado, the Dry

Movement uses resources that may otherwise be allocated to somatic maintenance or reproduction. How does increased energy expenditure affect resource allocation? Using the butterfly Speyeria mormonia, we tested whether experimentally increased flight affects fecundity, lifespan or flight capacity. W

Home-range sizes of adult, male yellow-bellied marmots (Marmota flaviventris) were estimated from radiotelemetry, trapping, and visual observation. Home ranges were monitored from early May to late August in 1989, 1990, and 1991. Home-range size varied greatly among males (range, 0.06–47.51 ha). Med

C. M. Haynes, T. A. Lytle, E. J. Wick, R. T. Muth, Larval Colorado Squawfish (Ptychochielus lucius Girard) in the Upper Colorado River Basin, Colorado, 1979-1981, The Southwestern Naturalist, Vol. 29, No. 1 (Mar. 23, 1984), pp. 21-33

The “Modern Synthesis” brought paleontology and systematics together with population genetics to endorse Darwin’s insights and to lay the foundation of steady progress in understanding.

Colorado Euphydryas editha populations completely isolated from well-studied West Coast populations for at least 7,000 generations show strong phenetic and, at seven of eight loci, genetic resemblance to them. The patterns of allozyme variation are not compatible with the hypothesis that the observe

To advance understanding of biodiversity and ecosystem function, ecologists seek widely applicable relationships among species diversity and other ecosystem characteristics such as species productivity, biomass, and abundance. These metrics vary widely across ecosystems and no relationship among any

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Haystack Cave, Gunnison County, Colorado, has provided the first collection of vertebrate remains from the Pleistocene (Rancholabrean) of western Colorado. Two carbon 14 analyses of bone apatite have produced dates of 14,935 ± 610 and 12,154 ± 1,700 years B.P. for this assemblage. This fauna, in con

The Colorado River is a critical source of water supply for 40 million people in nine states spanning two nations in western North America. Overallocated in the 20th century, its problems have been compounded by climate change in the 21st century. We review the basin’s hydrologic and water managemen

Temporal fluctuation in abundance is common in many wildlife populations, but the causes and consequences to population dynamics of these fluctuations remain poorly understood. We used long-term (1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(20

Studies in natural populations are essential to understand the evolutionary ecology of senescence and terminal allocation. While there are an increasing number of studies investigating late-life variation in different life-history traits of wild populations, little is known about these patterns in s

Gut microbes are believed to play a critical role in most animal life, yet fitness effects and cost-benefit trade-offs incurred by the host are poorly understood. Unlike most hosts studied to date, butterflies largely acquire their nutrients from larval feeding, leaving relatively little opportunity

Ants are ecologically dominant members of terrestrial communities. Ant foraging is often strongly associated with plants and depends upon associative learning of chemicals in the environment. As a result, plant chemicals can affect ant behaviors and, in so doing, have strong multi-trophic indirect e

Summary Vegetative traits of plants can respond directly to changes in the environment, such as those occurring under climate change. That phenotypic plasticity could be adaptive, maladaptive, or neutral. We manipulated the timing of spring snowmelt and amount of summer precipitation in factorial co