The niche of higher plants: evidence for phylogenetic conservatism

A species' ecological niche depends on the species' adaptations to its pres ent habitat, but also on the legacy from its ancestors. Most authors argue that such a phylogenetic niche conservatism is of minor importance, althoug h no quantitative analyses across a major taxon is available. Higher plants from central Europe offer a unique opportunity for Such an exercise, as th e niche positions along various environmental gradients are available for m ost species. We quantified niche conservatism by two approaches. First, we used a phylogenetic tree and quantified the degree of retention of niches a cross the tree. Depending on the gradient, the values ranged from 0.43 to 0 .22. This was significantly greater than the null expectation. Second, we u sed a taxonomy and quantified the amount of variance among species that cou ld be explained at higher taxonomic levels. The values ranged from 25 to 72 %. Again, this was significantly higher than the null expectation. Thus, bo th approaches indicated a clear niche conservatism. The distribution of con servatism across taxonomic levels differed considerably among environmental gradients. The differences among environmental gradients could be correlat ed with the palaeoenvironmental conditions during the radiation of the phyl ogenetic lineages. Thus, niche conservatism among extant plant species may reflect the opportunities of their ancestors during their diversification.