Imagine the tropics and what comes to mind?

Hot weather and colour. Think bright-feathered parrots, striking hibiscus flowers, exotic fruits and vibrant coral and tropical fish.

"We found tropical communities are less colourful than temperate communities. " Rhiannon Dalrymple, University of NSW

For a few hundred years people, including biologists, have thought life is more vibrant in the tropics than plants and animals in more temperate environments and the poles.

But ecologist Rhiannon Dalrymple is the first person to test this assumption.


And her research shows we may have been wrong all along. Tropical species are not more colourful than plants and animals living further from the equator, she found.

"On average, we found tropical communities are less colourful than temperate communities," said Dr Dalrymple, whose research formed part of her PhD at the University of NSW. "That is pretty surprising."

Colourful plants aren't confined to the tropics.

Colourful plants aren't confined to the tropics. Photo: iStock

Dr Dalrymple used a spectrometre machine to measure the colour of more than 500 species of bird, more than 400 species of butterfly and the flowers of more than 300 plant varieties.

She also measured UV colours levels, which humans cannot see, but which are visible to many animals.

"It didn't matter how we analysed the data, it does not show tropical species to be more colourful," she said.

"It's been pretty hard for the scientific community to swallow."

Dr Dalrymple said the idea that tropical species were more vibrant was very old.

"It was a big point of discussion amongst the influential evolutionary biologists and natural explorers in the 19th century," she said.

Researchers attempted to answer the question mid last century, but didn't have the techniques or equipment to measure colour.

"They could look at pictures and say whether they felt something was colourful but we didn't have the techniques to quantify colouration," she said.

Angela Moles, Dr Dalrymple's co-author and supervisor, said early explorers made a living collecting specimens of new or interesting plants and animals and would inevitably send back the brightest because they could make more money for their families.

"There's always been this collection bias," Professor Moles said.

Even bushwalkers tend to notice the radiant blue butterfly while ignoring the 15 brown coloured ones around them, she said.

"It's like many things in science where we believe we know what's going on and then we test it and find our preconceived ideas were wrong," she said.

The research has been published in the journal Global Ecology and Biogeography.

This article appeared in SMH