Social plants: in the wild, staghorn ferns grow in colonies to improve water storage for all members


Shutterstock/Florist_Yana

Kevin Burns, Te Herenga Waka — Victoria University of WellingtonSocial colonies are nothing new in the animal kingdom. We know bees, ants and termites live in large colonies, divide labour and co-operate to take care of offspring produced by a single queen.

This behaviour, known as eusociality, has evolved independently in insects, crustaceans (certain species of shrimp) and even some mammals (naked mole rats), but it has never been observed in plants. This suggested plants were somehow less complex than animals.

Our study, published this week, turns our understanding of the evolution of biological complexity on its head. It documents the life history of a remarkable species of fern that grows in the tops of rainforest trees on Lord Howe Island, a small volcanic island in the north Tasman Sea.

Rather than growing as individual ferns in the treetops, the staghorn fern (Platycerium bifurcatum) lives in colonies, in an adaptation to its harsh habitat high above the water and nutrients stored in the soil below.

Individuals differ markedly in size, shape and texture. But they always grow side-by-side within colonies, fitting together like puzzle pieces to form a bucket-like store of water and nutrients available to all colony members.

Many individuals forgo reproduction and instead focus on capturing or storing water to the benefit of other colony members.




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Life in the tree tops

Staghorn ferns belong to a group of tree-dwelling plants known as epiphytes. Tree canopies are a challenging environment for plants to grow. Without access to soil, epiphytes are regularly exposed to severe water and nutrient stress.

Epiphytes have evolved several ways to mediate the lack of access to water and nutrients. Bromeliads grow cup-shaped leaves, while orchids have specialised root tissues. But staghorn ferns have developed a colony lifestyle to overcome the problem.

Panorama taken on Lord Howe Island
On Lord Howe Island, staghorn ferns grow in colonies.
Author provided

Staghorn ferns can be bought at many garden stores and will grow like any other pot plant. But in the wild on Lord Howe Island, we discovered individual plants collaborate, specialising in different tasks in the construction of the communal water and nutrient store, often at the cost of their own reproduction — just like social insects.

This radically changes our understanding of biological complexity. It suggests major evolutionary transitions towards eusociality can occur in both plants and animals. Plants and beehives aren’t as different as they might seem.

For decades, scientists interested in eusociality argued for a strict definition — many felt the term should be reserved for only a select group of highly co-operative insects.

This perspective led to widespread scepticism about its occurrence in the natural world. Perhaps this is why it was overlooked for so long in one of horticulture’s most popular pot plants.

Evolution of biological complexity

Four billion years ago, life began as simple, self-replicating molecules. Today’s diversity arose from these simple origins towards increasingly complex organisms.

Evolutionary biologists think that biological complexity developed in abrupt, major evolutionary transitions, rather than slow and continuous changes. Such transitions occur when independent entities begin to collaborate, forming new, more complex life forms — such as, for example, when single-celled organisms evolved into multi-cellular organisms.

A microcopic image of one of the first complex multi-cellular plants, algae known as Volvox
Early in the evolution of plants, single-celled algae joined to form more complex structures.
Shutterstock/Lebendkulturen.de

Another example is the transition from unspecialised bacterial (prokaryotic) cells to cells with an enclosed nucleus and specialised organelles that perform particular functions, known as eukaryotic cells.

Co-operation underpins the evolutionary origins of organelles — they likely evolved from free-living ancestors that gave up their independence to live safely within the walls of another cell.




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There are eight commonly recognised major evolutionary transitions — and eusociality is the most recent. Eusocial animals differ from others in three fundamental ways:

  • they live in colonies comprised of different generations of adults
  • they subdivide labour into reproductive and non-reproductive groups
  • they care for offspring co-operatively.

Our observations over the past two years on Lord Howe Island found staghorn ferns meet these criteria.

In highly eusocial species, caste membership is permanent and unchanging. But in primitively eusocial species, individuals can alter their behaviour to suit many roles required by the colony. Staghorn ferns probably fit under the latter category.

Our ongoing research will determine the staghorn’s position along this continuum of eusociality. But, for now, we know plants and animals share a similar evolutionary pathway towards greater biological complexity.The Conversation

Kevin Burns, Professor, Te Herenga Waka — Victoria University of Wellington

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

A Victorian logging company just won a controversial court appeal. Here’s what it means for forest wildlife


Brendan Wintle, The University of Melbourne; Laura Schuijers, The University of Melbourne, and Sarah Bekessy, RMIT UniversityAustralia’s forest-dwelling wildlife is in greater peril after last week’s court ruling that logging — even if it breaches state requirements — is exempt from the federal law that protects threatened species.

The Federal Court upheld an appeal by VicForests, Victoria’s state timber corporation, after a previous ruling in May 2020 found it razed critical habitat without taking the precautionary measures required by law.

The ruling means logging is set to resume, despite the threats it poses to wildlife. At particular risk are the Leadbeater’s possum and greater glider — mammals highly vulnerable to extinction that call the forests home.

So let’s take a look at the dramatic implications for wildlife and the law in more detail.

Why is this ruling so significant?

The Federal Court agreed VicForest’s logging failed to meet its environmental legal requirements. In fact, the Federal Court dismissed every single ground of appeal but one. And it takes only one to win.

The ground that won the case was that the federal environmental law designed to protect threatened species — the Environment Protection and Biodiversity Conservation (EPBC) Act — did not apply to the logging operations due to a forestry exemption.

To understand the significance of these issues, it’s important to know a bit about the context.

In the 1980s and ‘90s, forestry was passed to the states to regulate. So-called regional forest agreements (RFAs) were struck between federal and state governments. The idea was that forestry would be conducted under these state-led RFAs, avoiding federal scrutiny.

This was meant to streamline procedures, and offer a compromise between sometimes conflicting objectives: conservation and commercially profitable forestry.

However, states weren’t necessarily meant to have absolute control, and a check-and-balance system was put in place. If a logging operation doesn’t follow the RFA requirements, then the federal law is called in.

That way, states have control, but there’s a backup safety net for threatened species (which the federal government has an obligation to protect under international law).

This backup safety net is what the original case was testing. Friends of the Leadbeater’s Possum sued VicForests, arguing the logging operations breached the Victorian RFA, and the organisation won the case.

In response to the original decision against VicForests, Nationals Senator Bridget McKenzie introduced a private members bill, seeking to strengthen logging’s exemption from federal scrutiny.

If passed, the bill would make forestry activities within RFA areas exempt from scrutiny under the EPBC Act, regardless of whether they follow RFA rules.




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Both the court decision and the bill respond to a need for industry certainty and seek to minimise opportunities for legal action against logging under the EPBC Act. But they remove any certainty for environmental protection.

What does this mean for wildlife?

RFAs were established with the best of intentions. But unfortunately, they haven’t been working to protect wildlife — a point made clear in the EPBC Act’s recent ten-year independent review.

As former competition watchdog chair Professor Graeme Samuel, who led the review, said in his final report:

there are fundamental shortcomings in the interactions between RFAs and the EPBC Act.

The RFAs haven’t been updated as they were meant to be, despite dramatic changes in the environment, such as from mega-fires, and the warming and drying climate. These factors totally change the game for forestry and forest-dependent wildlife, such Leadbeater’s possum and the greater glider, which are declining dramatically.

We are currently experiencing a global mass extinction event, and Australia is a global extinction leader. Australia is responsible for 35% of all modern mammal extinctions globally and has seen an average decline of 50% in threatened bird populations since 1985.

Cutting down trees may seem insignificant to some, in the scheme of things. But small effects can accumulate into huge declines, like a death by a thousand cuts.

Both Leadbeater’s possum and the greater glider depend on large old trees with hollows (that take more than 100 years to develop) for shelter. Without many of these trees, they cannot survive.




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Logging in Victoria has led to a decline in the number and extent of these particular trees, and reduces future large tree numbers. This makes the animals more vulnerable.

To avoid extinctions, we can’t afford to lose more ground by continuing practices that damage or remove habitat.

The writing is on the wall

But things could be changing soon. The Victorian government plans to ban native timber harvesting from 2030. This happens to be the same year a decades-old contract with a wood pulp and paper company expires, currently binding the state to provide pulp logs by a legislated supply agreement.

After 2030, paper, pulp, and timber products would be logged from plantations rather than native forests. The writing is already on the wall.

Protesters in a forest
An anti-logging protest in Toolangi State Forest in response to VicForests winning their appeal in the federal court.
Kira Whittaker

Whether it’s the federal or state governments in charge, forest management needs to be scientifically robust, with strong compliance, enforcement and governance. Otherwise, as we’ve seen, there’s a significant risk of slippage and loss of trust.

Even before the mega-fires of 2019-20, most Australians didn’t support native forest logging. After the fires, their worries increased, with a majority expressing concerns that Australia’s unique environment might never be the same.

And as a result of rising community expectations on how the environment is treated, some businesses have pivoted.




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Many companies now see being associated with environmentally poor outcomes as risky. Bunnings, for example, has already banned VicForests’ native timber. The World Economic Forum places biodiversity loss in the top five risks to the global economy. And a global taskforce is being established that could eventually see environmental disclosures as a new norm.

It’s clear the status quo has led to an alarming rate of species decline. This decline will only be locked in further if legal exemptions make it impossible to hold law-breakers to account.The Conversation

Brendan Wintle, Professor in Conservation Ecology, School of BioSciences, The University of Melbourne; Laura Schuijers, Research Fellow in Environmental Law, The University of Melbourne, and Sarah Bekessy, Professor in Sustainability and Urban Planning, Leader, Interdisciplinary Conservation Science Research Group (ICON Science), RMIT University

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