Phylogenetic Constraint, Absent Life Forms, and Preadapted Alien Plants: A Prescription for Biological Invasions

Abstract

Widely separated plant communities supported by similar physical environments can display much similarity in their life form spectra even though these communities are often floristically unrelated. Such structural similarity reveals the strength of the physical environment in natural selection, particularly for the height, position, and duration of the perennating bud—the underlying premise of Raunkiaer’s life form system. But similarities among communities in life form spectra can be limited in part by phylogenetic constraints within the native flora. Phylogenetic constraint has been forcefully and repeatedly demonstrated with the arrival into new ranges of species with novel life forms that have become invasive (i.e., alien species with life forms novel to a recipient community have often become persistent, prolific, and even dominant). Communities invaded by species with a heretofore unrepresented life form are exceptionally diverse, both geographically and environmentally, and include coastal foredune...