Flies and bees act like plant cultivators

Pollinator insects accelerate plant evolution, but a plant changes in different ways depending on the pollinator. After only nine generations, the same plant is larger and more fragrant if pollinated by bumblebees rather than flies, as a study conducted by evolutionary biologists from the University of Zurich reveals.

Not much plant sex happens without pollinator insects: Bees, flies or butterflies transfer the male pollen grains to the stigma of a plant's female style, thereby ensuring its sexual reproduction. Researchers from the Department of Systematic and Evolutionary Botany at the University of Zurich now reveal that pollinator insects also have a surprisingly strong influence on plant evolution.

Plants pollinated by bumblebees become more fragrant

For their experiment, UZH professor Florian Schiestl and doctoral student Daniel Gervasi used field mustard -- a kind of cabbage species and a close relative of oilseed rape. The researchers allowed one plant group to be pollinated solely by bumblebees for nine generations, another only by hoverflies and a third by hand. Afterwards they analyzed the plants, "which differed greatly," as Florian Schiestl explains. The plants pollinated by bumblebees were larger and had more fragrant flowers with a greater UV color component, which bees and their relatives see. The plants pollinated by hoverflies, on the other hand, were smaller, their flowers were less fragrant and they self-pollinated considerably more. According to Schiestl, the mechanism of evolutionary change is fact that different pollinators differ in their preferences and thus preferentially cross-pollinate specific plant individuals, much like a plant breeder using individuals with favorable properties. The flies' considerably lower pollination efficiency is the cause of the increase in self-pollination. The plants essentially help themselves if the pollinator transfers too little pollen.

Pollinator insects hasten plant evolution

The fact that the plants change so significantly already after nine generations came as a surprise to the researchers: "The traditional assumption is that evolution is a slow process," explains Schiestl. The evolutionary biologist from UZH draws the following conclusion from his results: "A change in the composition of pollinator insects in natural habitats can trigger a rapid evolutionary transformation in plants." This is particularly interesting as certain pollinator insects such as bees have been vastly decimated by the extensive use of pesticides and the depletion of the landscape in recent decades. According to Schiestl, it would thus be conceivable for plants to increasingly rely on flies as pollinators, which would result in the evolution of weaker flower fragrances and more self-pollination. In the longer term, this would reduce a plant population's genetic variability and the plants would become more susceptible to disease.

Read the paper: Real-time divergent evolution in plants driven by pollinators.

Article source: University of Zurich.

Image credit: UZH


How plants form their sugar transport routes

In experiments on transport tissues in plants, researchers from Heidelberg University were able to identify factors of crucial importance for the formation of the plant tissue known as phloem. According to Prof. Dr Thomas Greb of the Centre for Organismal Studies (COS), these factors differ from all previously known factors that trigger the specification of cells. The findings of the Heidelberg researchers substantially expand our understanding of the metabolic processes in plants. Their results were published in the journal Current Biology.

Scientists examine impact of high-severity fires on conifer forests

The ability of some Western conifer forests to recover after severe fire may become increasingly limited as the climate continues to warm, scientists from the Smithsonian Conservation Biology Institute (SCBI) and Harvard Forest found in a new study published in Global Change Biology. Although most of these cone-bearing evergreen trees are well adapted to fire, the study examines whether two likely facets of climate change -- hotter, drier conditions and larger, more frequent and severe wildfires -- could potentially transform landscapes from forested to shrub-dominated systems.

From Elsevier: 200 Years of Flora - free access to all articles

2018 will mark the 200th anniversary of the journal Flora. To kickstart the celebrations, all journals in the Elsevier archives have been scanned and have been added to ScienceDirect. Articles published before 1905 are available via the Biodiversity Library, and all articles from 1905 onwards are freely available via ScienceDirect until March 2020 and can be accessed through this page: https://www.journals.elsevier.com/flora/news/200-years-of-flora-free-access-to-all-articles.