Ecology and distribution of the butterflies of Southern Central Colorado

Abstract

The 160 resident and 18 migratory species of butterflies occurring in an area west of Pueblo, Colorado, were studied. The area contains a great variety of habitats from alpine tundra to plains grassland. Spatial and altitudinal distribution, habitats, number and timing of broods, and larval and adult foodplants, were studied. More than 100 new larval hostplant records are presented. Diversity is greatest in the foothills, and decreases with altitude except that the plains have low diversity similar to the high mountains above roOOO'. Distributions within the area are very consistent with altitudinal temperature gradients. Mountain barriers have not prevented the spread of butterflies to suitable habitats throughout the area. Postglacial warm periods apparently caused the extinction of alpine butterflies on Greenhorn Peak which is now above timberline. The area's butterflies are mainly western North American in distribution. Species composition differs somewhat from another mountain fauna just north of the area,due to an increased percentage of northern species there; both areas have similar percentages of eastern and western species. 109 of the 160 native species have only one brood per year. Time of flight is generally later at high altitude. Few onebrood species fly after July. At low altitude multi-brood species predominate. Ten populations differ in appearance from populations outside the area; these are described but not named. Most species in the Pueblo area occur in many plant associations. The most distinctive butterfly associations are those of the alpine zone and of riparian habitats. Other species are mostly restricted to pinyon-juniper woodland, Cercocarpus chaparral, or grassland habitats. Several species distributions are influenced by geological substrate. Most species often feed as adults, on flowers especially. Some species feed only on sap; several never feed as adults. Sap-feeding usually occurs as an alternative strategy for species which never feed on flowers.