Tree evolution
Plant life has existed on Earth for millions of years, with records of the first land plants dating from the Silurian period (350–320 million years ago). The huge success of trees in evolutionary terms is due to their ability to adapt to a wide variety of environments.
The earliest trees were conifers, which arose in the Permian period (220–195 million years ago), but it was not until toward the end of the Cretaceous period (140–70 million years ago) that forest vegetation had evolved into tree types that we would recognize today. By this
time, forests contained trees that were similar to planetree, magnolia, poplar, and fig. Such flowering plants were better equipped to spread to new areas than earlier flora. This spread was dictated by geographical and climatic changes. Another advantage of flowering trees was their association with pollinating insects such as bees; this enabled the plants to colonize a wide diversity of new sites.
PREHISTORIC FOREST
Prehistoric forests were dominated by tree ferns and giant horsetails creating areas of dense vegetation, as here in the Yarra Ranges National Park, Australia.
TREE MIGRATION
Trees respond to changes in conditions on Earth by adapting their size and shape morphologically or by “moving.” A tree population moves by successfully seeding in the direction of the most favorable conditions. In this way, modern trees have survived ice ages and global warming or global cooling for millions of years.
CONTINUING EVOLUTION
Tree evolution is a continuing process. Today there are species that are particularly unstable and prone to crossbreeding with near relatives. However, the resulting progeny are occasionally better suited to prevailing conditions than the original tree and are therefore more likely to survive and reproduce.
