Let’s show a bit of love for the lillipilly. This humble plant forms the world’s largest genus of trees – and should be an Australian icon

You’re probably familiar with the sight of a lillipilly bush. This hardy Australian staple – a glossy evergreen bearing powder-puff flowers and clusters of bright berries – features in many a garden hedge.

But you may not know this humble native has spread across the globe in waves of emigration, adaptation and evolution. Almost 1,200 species of lillipilly are now found in rainforests across the tropics and subtropics of Africa, Asia and the Pacific.

Our research helped reconstruct the evolutionary history of lillipillies in unprecedented detail. We show how lillipillies evolved in Australia and now form the largest genus of trees in the world.

Lillipillies are one of Australia’s great gifts to the natural world. But the story of these homegrown heroes may be taking a grim turn.

A plant on the move

Lillipillies began their international adventures about 17 million years ago. At that time, the Australian continent (which together with New Guinea is known as the Sahul Shelf) was colliding with Southeast Asia (known as the Sunda Shelf) following its breakup with Antarctica. This breakup was the final dramatic act of the fragmentation of Gondwana.

The collision provided opportunity for biotic exchange between the northern and southern hemispheres. Many plants and animals moved south to the Sahul Shelf and prospered in the new lands. Lillipillies are one of the few lineages that moved in the other direction.

Along with our songbirds, lillipillies stand as a rare example of an Australian group that set out from these shores and achieved major evolutionary success abroad.

Lillipillies light up our lives when they flower and fruit. Their showy white, cream or red flowers are followed by succulent red or purple berries. They’re a magnet for pollinators, helping fill our gardens with the songs of insects and birds.

The riberry, Syzygium luehmannii, is one of the most commonly grown and stunning garden species. It produces heavy crops of delicious fruit rich in antioxidants and prized by chefs.

Many species in the genus are used as food and medicine by Indigenous people, and potent antibacterials have been identified in the leaves of some species. Cloves, a favourite spice of home bakers, are the dried flower buds of an Indonesian lillipilly – the aptly named Syzygium aromaticum.

About 75 species of lillipilly are native to all Australian states and territories except South Australia and Tasmania.

The greatest concentration of species is in the Wet Tropics World Heritage Area of northeast Queensland. About 50 species are found there, half of which occur nowhere else on Earth.

And almost 1,200 species of lillipilly are now found in rainforests across the tropics and subtropics of Africa, Asia and the Pacific, including Australia.

As is common in the tropics, species new to science are regularly discovered and named. For example, almost 30 new species of lillipilly have been named from New Guinea in the last two years – and many more are likely awaiting scientific discovery.

But how did lillipillies achieve such international success? Our research team decided to find out.

Peering into the past

The research, led by colleagues in Singapore, involved analysing the genomes of hundreds of living species of lillipillies.

Similarities and differences in the structure of genomes can reveal how closely related the species are. Using that knowledge, we can build up a picture of their genealogy - the “family tree” that connects ancestral species and their descendants.

These techniques also allow us to estimate the amount of genetic change that has occurred along the branches of the genealogy. And, if we’re lucky enough to have an accurately dated fossil of an ancestral species – as we do for lillipillies – we can calculate the rate of genetic change even more accurately.

All this allowed us to peer deeply into the past and reveal the events that set the lillipillies on their global journey.

We already knew lillipillies evolved in Australia and emigrated into the rainforests of Africa, Asia and the Pacific. Our research showed this dispersion occurred in at least a dozen distinct waves.

Each emigrant lineage diversified rapidly and successfully in its new environment. This resulted in the nearly 1,200 lillipilly species found worldwide today – more than any other tree genus. In contrast, their relatives the eucalypts have largely remained only a local success story.

A sad twist?

Lillipillies may be one of Australia’s most successful botanical exports, but their future, like that of many rainforest plants globally, is threatened by habitat degradation and climate change.

The Magenta Cherry (Syzygium paniculatum), for example, is endangered by coastal development in New South Wales. And the Brotherly Love Lillipilly (Syzygium fratris), found only on Queensland’s highest mountain, is highly vulnerable to climate change.

But a devastating disease – myrtle rust - may be the most potent threat of all. It’s caused by an introduced fungal pathogen and kills new foliage, flowers and fruits of plants in the family Myrtaceae, to which lillipillies belong.

Myrtle rust arrived in Australia in 2010 and spread rapidly in the wind and via human activity. Already, it threatens some plant species with extinction. Lillipilly species have been damaged by this serious disease, though none are under immediate extinction threat yet.

Lillipillies are an Australian origin story. They’re a major contributor to rainforest biodiversity and important to Indigenous cultures. And they’ve endeared themselves to generations of gardeners and cooks.

Given all this, lillipillies deserve to be recognised – and protected – as Aussie icons.

Darren Crayn, Professor and Director, Australian Tropical Herbarium, James Cook University

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

Want noisy miners to be less despotic? Think twice before filling your garden with nectar-rich flowers

Noisy miners are complicated creatures. These Australian native honeyeaters live in large cooperative groups, use alarm calls to target specific predators, and sometimes help raise the young of other miners. But they’re perhaps best known for their aggressive and coordinated attacks on other birds – a behaviour known as “mobbing”.

We conducted a study investigating some of the possible factors that influence mobbing. We were interested in whether access to human food left on plates at cafes, or a high nectar supply thanks to planted gardens, might give urban miners extra energy and time to mob other species more often. We also examined whether miners were more aggressive towards some species over others.

Our study, published in the journal Emu - Austral Ornithology, found it wasn’t cafes with access to sugar-rich food that led to more miner aggression. In fact, gardens were where we recorded the highest amount of aggressive behaviour.

Understanding mobbing is important, because this behaviour can drive out other birds and reduce diversity. Smaller birds with a similar diet to noisy miners are particularly vulnerable.

What we did

The noisy miner’s preferred habitat is along the edges of open eucalypt forest, including cleared land and urban fringes. Their numbers have grown in recent decades, presenting a significant conservation problem.

We know from previous research that urban noisy miners tend to be more aggressive compared with rural populations.

But to examine mobbing behaviour more closely, we placed museum taxidermies (stuffed animals) of different species of birds in three different types of habitat around Canberra:

• urban cafes with lots of food leftovers

• urban gardens that had higher-than-usual supplies of nectar

• bush areas more typical of “natural” miner habitat.

For each habitat, we then presented the resident noisy miners with three different types of museum taxidermy models of birds:

• food competitors with a similar diet to miners, both of the same size (musk lorikeets) and a much smaller species (spotted pardalote)

• potential predators, including a dangerous species that preys on miners (brown goshawk) and a species that robs nests but poses less of a risk to adult miners (pied currawong)

• neutral species, meaning a bird that does not prey upon nor compete with miners for food (in our study, we used a model of an eastern rosella).

We wanted to see how miners responded to these “intruders” in various settings. We also set up a speaker nearby to broadcast alarm calls, to see how miners reacted.

What we found

We found interesting differences in how miners responded to our taxidermy models and the broadcasted alarm calls.

Noisy miners exhibited aggressive behaviours for a much longer time in gardens and cafés in comparison to natural bush areas.

Surprisingly, however, access to sugar-rich food from cafes didn’t yield the most aggressive behaviour. Rather, we recorded the highest levels of aggressive behaviour near garden sites.

Nectar-rich plants (such as grevilleas and bottlebrushes) are attractive to birds with a sweet tooth, and miners are no exception. Newer cultivars flower for longer, meaning miners living in our gardens may have access to an almost year-round source of food.

Ready access to these flowering shrubs may affect aggression by providing more time, energy or reward to noisy miners defending these uber-rich resources.

The type of model presented also impacted miner response.

More miners were attracted to an area and mobbed the subject for longer when the model was of a predator.

Miners showed even greater aggression to food competitor models, however. They were more likely to physically strike food competitor models with a peck or swoop compared to predator models.

What can gardeners do with these findings?

Our research shows the importance of considering how gardens – whether in back yards, in parks or new housing estates – can affect local ecosystems, including bird behaviour. Previous studies have drawn a link between the types of plants humans choose to plant and the local mix of bird species.

To reduce the risk of creating a perfect habitat for despotic miners in your garden, aim to:

• plant multi-layered levels in your garden – that means including ground cover, small shrubs, medium shrubs and trees to provide shelter at different heights for various birds and animals

• consider planting plenty of dense shrubs with small flowers to attract insects and provide shelter for small birds

• use a mix of nectar-rich and non-flowering shrubs and grasses (instead of focusing too heavily on flowering plants)

• try to avoid planting too many exotic species; opt instead for native plants local to your area and suited to the climate, as these benefit native plants and animals whilst minimising benefits to aggressive noisy miners.

Jade Fountain, PhD Student, University of Adelaide and Paul McDonald, Professor of Animal Behaviour, University of New England

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