Plants are nature’s niche conservatives

A survey of over 11,000 plant species from the southern hemisphere has found that while their environment may shift, they rarely do.

Researchers led by Professor Mike Crisp of the Australian National University undertook a study of seven plant habitats, or ‘biomes’, to see whether plant species stayed in the same kind of environment over evolutionary time and across continents.

They found that over tens of millions of years, only 3.6 per cent of plants had shifted between biomes, the vast majority retaining their ancestral ecology. “(B)iome statis at speciation has outweighed biome shifts by a ratio of more than 25:1,” they write in their paper, published online in advance today in Nature.

This has implications in light of habitat contraction due to climate change, they say. It also has implications for better understanding invasive species.

The team studied plant species in Africa, Madagascar, Australia-New Guinea, New Caledonia, New Zealand and South America and separated them into seven biomes: wet forest, sclerophyll, alpine, bog, temperate grassland, savannah and arid.

In all biomes, shifts were rare, with plants showing their true niche conservative colours. Of those that did shift, most were within landmasses and only a few were due to colonisation over the oceans. Of those that did travel over the oceans, the species tended to be found in the same biome as their ancestors, and there were no transitions between strongly contrasting biomes such as arid and bog or savannah and alpine.

Niche conservatism might be expected in ancient plants that grew on the Gondwanan land mass, but even species that have diversified greatly in the last 20 million years tended to be just as conservative, the researchers say.

Those recently diversified plants may have resulted not from adaptation to new biomes but from expansion within their biome as climate changed.