Shifts in flowering phases of crops on account of diminished insect density — ScienceDaily


It still sounds unlikely today, but a decline in insect numbers could make it common in the future: fields full of flowers but no bees in sight.

A research group from the University of Jena and the German Center for Integrative Biodiversity Research Halle-Jena-Leipzig (iDiv) has found that insects have a decisive influence on biodiversity and the flowering phase of plants. If there is a lack of insects where the plants grow, their flowering behavior changes. This can mean that the life cycles of the insects and the flowering times of the plants no longer coincide. If the insects seek nectar at the wrong time, some plants will no longer be pollinated.

Innovative research method in iDiv Ecotron

Ecosystems are changing worldwide, especially due to global warming and changing land use. Insect species are dying out and the insect biomass is decreasing. Researchers have therefore investigated how the biodiversity of plants changes in the context of climate change. For this purpose, different climate scenarios with different temperatures and precipitation were simulated.

In a new study, which was published in the journal Frontiers in Plant Science, the working group Biodiversity of Plants at the University of Jena, headed by Prof. Christine Römermann, presents a different research approach. In collaboration with scientists from iDiv under the direction of Prof. Nico Eisenhauer, the researchers concentrate on the influence of invertebrates such as insects on the diversity of species and the flowering behavior of plants.

“We know that insect biomass is decreasing,” says Josephine Ulrich, a doctoral student from Römermann’s team, in a 2017 study that found that insects have decreased by 75 percent over the past 30 years.

The Jena research group has now for the first time examined in detail to what extent a decreasing insect density influences plant development. While earlier studies had only carried out field tests, the research team used the “Ecotron”, an iDiv research facility in which identical climatic situations can be simulated in artificial ecosystems and observed with cameras.

In their experiment, the researchers investigated how plant composition and plant development change when the number of insects falls by three quarters.

Mismatch between plant and animal worlds

Ulrich and her colleagues discovered that the reduced insect biomass causes a change in plant species. It is mainly the dominant plant species such as red clover that are becoming increasingly common. The development of the flowering period also changes with decreasing insect density. Some of the plants studied bloomed earlier and others later.

“These changes can lead to mismatches between plant and animal species, which has a detrimental effect on the ecosystem,” says Ulrich, the lead author of the study. Examples are the food supply with insects and the success of pollination. This deterioration in ecosystem function could lead to further losses of insect and plant species. Another consequence could be that plants are increasingly attacked by pests. Due to the decreasing number of insects that feed on aphids, for example, these pests could spread unhindered.

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Materials provided by Friedrich Schiller University Jena. Note: The content can be edited by style and length.