When animal and plant populations move up and out
Plants are not always as static as they seem. While most individual plants stay relatively still compared to most animals (no, not all), plant populations can shift laterally over time in an analogous way to animal populations. The main difference is the rooted nature of plants means that they move slowly, across generations. The cause of this is usually environmental: the species is shifting as the climate changes or as competition or another form of pressure encroaches it. Richard Brusca and colleagues have published the results of a plant survey in Arizona which shows that species distributions have changed in the last 50 years. Since a survey carried out by Robert Whittaker in 1963, the vegetation on an area of the Catalina Mountains has crept its way higher up the mountain. Given the difference requirements and tolerance range of different plant species, the entire vegetation does not shift simultaneously or equally; this means that community composition has changed as some plan