The scent of a flower varies locally
“At one location it may be a pinewood scent, in another root beer and a little further south perhaps perfume,” says Magne Friberg, senior lecturer at the Department of Biology at Lund University.
He and his colleagues have studied floral scents for eight years in 94 populations of woodland star plants of the genus Lithophragma, on the west coast of the USA. When the researchers studied the floral scent of the entire plant genus, they discovered that the scent varies widely even over relatively small geographical distances. Sometimes the scent of individual plants of the same species that are growing some 10 kilometres from each other are completely different.
The local scent attracts moths of the genus Greya for pollination, and the plant populations and moths have coevolved over a long period. The evolutionary process has resulted in the flowers evolving a unique scent within a small area, and that the moths in the same area in turn evolved into local specialists attracted by the specific local scent, not recognizing woodland star scents from other species and populations than the local one.
The floral scent differences are genetic and not due to factors such as degree of humidity, soil type or nutrient levels.
“We know this because the differences remain when we grow plants from different populations of the same species in a greenhouse environment”, says Magne Friberg.
According to the researchers, the discovery is important when implementing measures if a population or species of plant is endangered – a scenario that may occur more frequently when the climate changes.
Co-author John Thompson, whose laboratory has long studied coevolution between plants and animals argues that “these are the kinds of studies we need if we are to make scientifically informed plans for conserving the earth’s many highly coevolved interactions at a time when environments are changing quickly. These results tell us that species coevolve as a geographic mosaic in which each local interaction between species may include unique evolutionary solutions. If we are to conserve species in a world in which environments are changing rapidly, we need to conserve as many of these links as possible.”
“In this case, it is probably not possible to move plants with a root beer scent to an area where endangered populations of the same plant have a pinewood scent, and believe that it can help. There is a considerable risk that the pollinators will not recognise the root beer scent and that the plant population does not recover”, explains Magne Friberg.
Conversely, the moths are completely dependent on finding the flower in which they specialise. They mate on the flower, drink nectar and lay eggs in the flowers, and will not survive in an environment where they cannot identify their host and nectar plants.
The work began eight years ago, when Magne Friberg was a postdoctoral associate in John Thompson’s laboratory at UC Santa Cruz. Friberg, who is now on the faculty at Lund University and the leader on this project, has continued to collaborate with Thompson since then. Christopher Schwind helped find plants in many remote ecosystems throughout far western USA. Robert Raguso from Cornell University is a specialist in chemical ecology and plant-insect interactions, and brought expertise not only the methods needed for analysis of these complex floral bouquets but also on interpretation of the wide range of biochemical pathways used by woodland stars. Paulo Guimarães, Jr. from University of São Paulo, who is a specialist in ecological and evolutionary network theory, brought expertise on how to interpret the complexity of these floral scents. It is the kind of collaborative research that is the hallmark of most modern science.
Friberg M, Schwind C, Guimarães Jr PR, Raguso RA, Thompson JNT. 2019. Extreme diversification of floral volatiles within and among species of Lithophragma (Saxifragaceae). Proceedings of the National Academy of Sciences, USA, in press