Natural Selections

Introductions, both accidental and purposeful, frequently have tragic consequences American elms, Ulmus americana , are native to North America from Saskatchewan to Nova Scotia and from Texas to Florida. They grow 60 to 80 feet tall, with a thick trunk, the shape of a vase and a domed crown 40...

The flowers of salt and pepper are tiny and arranged into compound groups called umbels, or bouquets in the shape of an umbrella

Two simple contrasts illustrate how the environments occupied by tiger whiptails differ in fundamental ways A long slender lizard moved among trees in a pinyon-juniper woodland on the Colorado Plateau, searching the accumulated debris beneath the trees for grubs, spiders, beetles or any other insects. It stopped when it saw...

Understanding genetic diversity in a species is especially important for conservation and restoration efforts

The world is full of robber flies—approximately 7,000 species have been recognized worldwide and 1,000 are native to North America

The persistence of two colors everywhere suggests a balance of evolutionary forces

From the caliche soils of southeastern Colorado to crevices in bare sandstone on the Colorado Plateau, stemless four-nerved daisies show remarkable variation in growth form