Colloquium paper: a phylogenetic perspective on the distribution of plant diversity

Abstract

Phylogenetic studies are revealing that major ecological niches are more conserved through evolutionary history than expected, implying that adaptations to major climate changes have not readily been accomplished in all lineages. Phylogenetic niche conservatism has important consequences for the assembly of both local communities and the regional species pools from which these are drawn. If corridors for movement are available, newly emerging environments will tend to be filled by species that filter in from areas in which the relevant adaptations have already evolved, as opposed to being filled by in situ evolution of these adaptations. Examples include intercontinental disjunctions of tropical plants, the spread of plant lineages around the Northern Hemisphere after the evolution of cold tolerance, and the radiation of northern alpine plants into the Andes. These observations highlight the role of phylogenetic knowledge and historical biogeography in explanations of global biodiversity patterns. They also have implications for the future of biodiversity.

Fig. 1.

Major patterns in the movement of plant lineages discussed here. (Upper) Hypothesized movements in both directions of now disjunct tropical lineages across the North Atlantic during the early Tertiary. (Lower) (1) Hypothesized originations of adaptation to cold, seasonal climates, perhaps predominantly in Asia. (2) Iterated movement more recently of temperate lineages around the Northern Hemisphere, especially through Beringia, and perhaps predominantly out of Asia. (3) More recent New World movements of lineages adapted to high elevations, especially from North America into the Andes of South America over the last 5 million years. Base maps for the Eocene (≈50 million years ago) (Upper) and the Miocene (≈14 million years ago) (Lower) are based on C. R. Scotese's PALEOMAP Project (www.scotese.com). Darker gray areas show the hypothesized distribution of tropical climates during those time periods (see ref. 14).