Grassland, meadow, tundra, or any other area in Glacier suitable for
plant growth and supplied with abundant sunlight produces an
extravagance of wildflowers. This display of various shapes and
colors is neither an accident nor a mere decoration of nature. Nor
would Earth’s recent explosion of mammal and bird species have been
possible without the evolution of flowering plants.
Two hundred million years ago, early in the Age of Reptiles,
angiosperms (flowering plants) had not yet evolved. Plant
reproduction still relied on spores and cones. Then, during the
Cretaceous Period, the last sediments were being laid down in the
inland sea that covered most of Montana. (It was these sediments
that the ancient Precambrian rocks of Glacier’s mountains later
overrode, forming the Lewis Overthrust.) During this period the
evolutionary miracle occurred: flowering plants—grasses, vines,
shrubs, broadleaf trees, wildflowers—inherited the Earth.
The timing was important. As Earth’s tropical climate gradually
changed to temperate extremes during this period, the domination of
cold-blooded dinosaurs ended and the moisture-demanding coniferous
forests that had covered the earth in green monotony began to
shrink. Angiosperms provided a solution to the ecological void:
grasses and forbs grew where trees no longer could. Most important,
relationships evolved between this new class of plants and the
relatively few species of insects then existing.
Insects began to use the pollen of flowering plants; the
angiosperms, in turn, evolved bright petals and nectar that
exploited visiting insects for the plants’ own reproductive
purposes. This partnership allowed insects to diversify rapidly,
evolving new, specialized forms such as bees, moths, and
butterflies. As a result, predatory forms of insects and arachnids
also rapidly diversified.
The most dramatic change, however, involved warm-blooded birds and
mammals, whose high rates of metabolism required high-energy fuels.
Unlike gymnosperm seeds, which contain no protective covering,
angiosperm seeds are surrounded by a fruit. The development of these
highly nutritious seeds, and the attendant explosion of insect
species, ensured survival of the newly evolved birds.
As birds diversified into seed-eaters, insectivores, and carnivores,
mammals, then uncertain little ratlike creatures darting among the
feet of dinosaurs, began a rapid rise to dominance; grasslands
promoted an explosion of herbivorous and carnivorous species.
The evolution of angiosperms, and the animal revolution it made
possible, came with amazing speed. Most significant, it was a vital
first step upon which the meteoric rise of man depended.
[Illustration: Indian paintbrush is common at all elevations below
tundra. It may be white, yellow, orange, pink or red. The actual
flowers, inconspicuous and green, are surrounded by brilliantly
colored bracts. Semi-parasitic on other plants, paintbrush is
normally found growing in conjunction with other wildflowers; its
roots steal sustenance from neighboring plants.]
[Illustration: Yellow stonecrop, widely distributed in forest and
scrub-forest zones, is one of the park’s few plants having succulent
leaves, an adaptation that helps it survive in such situations as
dry, rocky outcrops.]
[Illustration: The Calypso orchid grows in the cool, shadowed forest
where light is dim. It lives in partnership with certain fungi that
exist about the orchid’s roots and seem to help nourish it.]
[Illustration: Silky lupine, a legume, has nitrogen-fixing nodules
on its roots, thus allowing it to grow in nitrogen-poor soil. It is
widely distributed in grassland and forest communities.]