Results of a demographic study of Helianthella quinquenervis (aspen sunflower, Asteraceae) within plots at 2,900m at the Rocky Mountain Biological Laboratory. Note that seedlings are not common in most years, and the overall population seems to be declining. The lack of seedlings in most years is a consequence of frost damage to flower buds the previous year (so no seeds were produced). The...

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Excavated plants of Helianthella quinquenervis (aspen sunflower, Asteraceae). H. quinquenervis is a long-lived perennial (some individuals can live 50-75 years). Note that each plant has multiple ramets from a single root.

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Photo of an early-stage inflorescence of tall larkspur (Delphinium barbeyi) after a mid-June snowstorm at the Rocky Mountain Biological Laboratory. The buds were killed by the cold temperature. Like Helianthella quinquenervis, D. barbeyi is a frost-sensitive species.

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Delphinium barbeyi, or tall larkspur, flowering in a year with no frost damage. Photographed (by David Inouye) in front of Gothic Mountain, at the Rocky Mountain Biological Laboratory. Altitude about 9,500 ft (2,900m).

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A female broad-tailed hummingbird (Selasphorus platycercus) in Colorado visiting tall larkspur (Delphinium barbeyi). The hummingbirds migrate north from Mexico each spring. Larkspurs serve as an important food source for them and for bumble bees. But larkspurs are also susceptible to frost, impacting the species that feed on them.

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