Tiny treetop flowers foster incredible beetle biodiversity

Hundreds of beetle species seem to be specialists that feed only from small white flowers on trees.
Susan Kirmse, CC BY-ND

Caroline S. Chaboo, University of Nebraska-Lincoln

The Research Brief is a short take on interesting academic work.

The big idea

Biologists have long known that rainforest treetops support a huge number of beetle species, but why these canopies are so rich in beetle diversity has remained a mystery. New research by my colleague Susan Kirmse and me shows that flowering trees play a critical role in maintaining this diversity, and that beetles may be among the most diverse pollinators in the animal kingdom.

We carried out a one-year study in a remote part of the Amazon rainforest in Venezuela. We used a specially built crane to collect a total of 6,698 adult beetles representing 859 species. These were gathered from 45 individual trees of 23 different tree species.

We were surprised to discover that the majority of these beetles – 647, or 75.3% of species found – were living on flowering trees. In fact, 527 beetle species in 41 families were associated exclusively with flowers. Interestingly, the majority of these species – almost 60% – were exclusively found on trees that produce lots of small white flowers.

Overall, this discovery shows that flowering trees are likely among the most important drivers for maintaining the high diversity of beetles in rainforests. But this relationship goes both ways. Our study also suggests that beetles may be among the most underappreciated pollinators in tropical forests.

A tall metal structure emerging from the forest canopy in Venezuela.
Using a specialized crane, the team was able to collect beetles from the very top of the forest canopy.
Susan Kirmse, CC BY-ND

Why it matters

Tropical rainforests are the very heart of Earth’s biodiversity. They harbor about 65% to 75% of all terrestrial species, including the most tree species and the most insects.

After finding such a tight relationship between beetles and flowering trees, we wondered: How many beetle species could be involved in pollination in the Amazon? Our study found an average of 26.35 unique beetle species for every species of tree. With an estimated 16,000 Amazonian tree species, this suggests that there might be more species of flower-visiting beetles than any other insects on Earth, potentially surpassing by far the 20,000 species of bees and the 19,000 species of butterflies.

Our study shows that flowering tree species play an important role as diversity hotspots in tropical rainforest canopies. For policymakers and biologists hoping to preserve or restore rainforests, promoting the cultivation of trees and other plants – especially those with lots of small white flowers that beetles love – could help to maintain species-rich communities. Flowers are a very important resource, providing food and shelter for thousands of insects in addition to beetles. Thus, preserving plant diversity or selecting many different indigenous tree species for reforestation can enhance the diversity of insects.

An image of a iridescent green-blue beetle.
Beetles like the Griburius auricapillus are just some of the hundreds of species that can be found in treetops.
Susan Kirmse, CC BY-ND

What still isn’t known

Our research was the first to describe this tight relationship between beetles and rainforest trees, especially with trees that produce thousands of small, simple flowers. But how this association came to be is still unclear.

Many of the beetle species were found only on trees with this particular type of flower. The trees get an obvious benefit: pollination. But what specifically these trees offer to the beetles requires further study. The simpler flowers are easier for beetles to access, but is the appeal food, like petals, pollen or nectar? Or maybe a home to find mates or lay eggs for the young to grow?

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What’s next

To fight the worldwide rapid declines in insect diversity, researchers and conservationists must understand the ecological connections between insects and their food plants. Long-term studies, particularly in research plots like the one we used in Venezuela, allow researchers to collect layers of information that help unravel the complexity of diversity.

Yet such sites rely on political interest and stability. Political instability in Venezuela is preventing our fieldwork from continuing at the Venezuela plot.

While we can’t return to our study site in Venezuela, it is clear that researchers must work together to understand the mysteries of life on Earth. But biologists are racing the clock as large rainforests are destroyed forever.The Conversation

Caroline S. Chaboo, Adjunct Professor in Insect Systematics, University of Nebraska-Lincoln

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How the humble dung beetle engineers better ecosystems in Australia

Paul Weston, Charles Sturt University and Theo Evans, University of Western Australia

Dung beetles play an important role helping clear up all the dung left by other animals in an environment.

In Australia there are approximately 475 native species of dung beetle.

But there’s a problem. Most of them are adapted to deal with marsupial dung. When British colonisers brought livestock down under, they introduced an entirely new type of dung that the native dung beetles were ill-equipped to handle.

Read more:
French beetles flown in to clean up Australia’s cattle dung

Not touching that dung

Cattle dung is wet and bulky. It is very unlike marsupial dung – which is typically small, dry pellets – and so the native dung beetles largely left it alone. As a result, large deposits of cattle dung accumulated in the Australian agricultural landscape.

Besides fouling the land, the dung was an excellent breeding site for bush flies and other nuisance insects, as well as internal parasites that plague the digestive tracts of livestock.

So CSIRO embarked on an ambitious plan to introduce into Australia many dung beetles that were adapted to livestock dung. Starting in 1966, it imported and released 43 species of dung beetles over 25 years.

The beetles came from places such as South Africa, France, Spain and Turkey. The chosen beetles had similar climate requirements and were adapted to wild and domestic livestock, so they could live in Australia and process livestock dung.

What do dung beetles do?

When people think of dung beetles, the popular image that comes to mind is that of an industrious beetle labouring to roll a large ball of dung across the landscape.

These little engineers are actually trying to find a suitable spot to situate the ball, on which they will lay an egg. Their offspring will have food and a safe place to grow up, and generate more dung beetles.

Most species of dung beetles actually tunnel beneath piles of dung and drag bits of it into subterranean chambers, where they then lay their eggs.

The larvae develop over the following weeks to months, eventually emerging as adults and crawling to the surface in search of a mate and another pile of dung to colonise.

The introduced dung beetles

Of the 43 species introduced to Australia by CSIRO, 23 have become established and many are having a positive impact.

The activities of dung beetles helped remove dung from pastures and with it, the breeding site for nuisance flies and internal parasites.

They also improved pasture fertility. They increased the permeability of pasture soils to rainwater which decreased runoff of rainwater laden with nutrients that can pollute waterways.

But it is not known just how widely each of the introduced species has spread. There might be geographical and seasonal gaps in dung beetle activity that could be filled by other species yet to be introduced to Australia.

Working with farming

Dung beetles have been around for tens of millions of years, but their ability to survive in modern agricultural environments may be jeopardised by some farming practices.

Tilling paddocks used in cropping and livestock rotation systems may destroy the developing dung beetle larvae.

Some deworming agents, used by livestock producers to control intestinal parasites, may pass through the livestock and out in their faeces, and might poison the dung beetles colonising the dung.

It should be possible to manage tillage and deworming to minimise harm to the dung beetles, and so maximise their positive impact on the land.

Read more:
Five things dung beetles do with a piece of poo

That’s where Dung Beetle Ecosystem Engineers (DBEE) comes in.

In this project, a group of research institutions, producer groups, land management groups and dung beetle entrepreneurs are working together.

The project, now in its second year, is supported by Meat and Livestock Australia and funded by the Rural Research and Development for Profit Program of the Australian Department of Agriculture, Water and the Environment. Charles Sturt University leads the project, with cooperators at CSIRO, University of Western Australia, University of New England, Mingenew-Irwin Group, Warren Catchment Council, Dung Beetle Solutions International, and LandCare Research NZ.

Dung Beetle Ecosystem Engineers aims to:

  1. understand the distribution of dung beetle species previously introduced to Australia, and predict their ultimate spread

  2. evaluate new species of dung beetle for importation and release into Australia

  3. estimate the economic impact of dung beetles on farming systems

  4. develop a database of information on dung beetles in Australasia and educational materials for use by a range of users

  5. work with farming and land management groups to engage landholders in detecting dung beetles and modifying agricultural practices to enhance the success of dung beetles.

At the end of the DBEE project, we will have a better understanding of the role of dung beetles as a farming tool, helping farmers choose agricultural practices that will improve their bottom line.

New dung beetle species will be ready to work for Australia and New Zealand, and a distribution network will enhance their spread to new geographic areas.

DBEE aims bring economic and ecological benefits to the agricultural sector and wider Australian and New Zealand community.The Conversation

Paul Weston, Senior Research Fellow / EH Graham Centre for Agricultural Innovation, Charles Sturt University and Theo Evans, Associate Professor , University of Western Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.