Tag Archives: australia

The Case of the Cool Invader: How Animals Cope With New Temperatures

This is a guest post by Dr. Monica Mowery.

Title Image Credit: John Tann, CC BY 2.0, image Cropped

Invasive Widow Spiders Perform Differently at Low Temperatures than Conspecifics from the Native Range (2022) Mowery, Anthony, Dorison, Mason & AndradeIntegrative and Comparative Biology. https://doi.org/10.1093/icb/icac073

The Crux

With increasingly clear effects of global climate change, everyone’s thinking about how we will handle extreme temperatures and weather events as they become more common. Less obvious is the fact that the changing climate is also rearranging global food webs, with many species readjusting in the fact of a new range of temperatures. This might not sound fantastic (and let’s face it, it’s not), but this changing climate may be able to teach us something about how species adapt to higher or lower temperatures.

Temperature plays a key role in determining whether an invasive species can take up residence in a new region. We know that low temperatures can be particularly limiting to newly-invasive species, especially insects and spiders. Yet few studies look at how lower temperature in a new environment can affect the survival, development, and behavior of new invaders.

We tested whether invasive widow spiders from a warm climate (Australia) adapted over generations to the lower temperatures of their invaded habitat in Japan. The move to Japan should require adapting to lower temperatures, but it might not, for a few reasons. Spiders from both locations may be equally good at coping with cooler or warmer temperatures, or, since urban areas are typically warmer than natural habitats, organisms that move between urban habitats might avoid facing the low temperature constraints.

Did You Know: Cities as Heat Islands

It’s hot in cities! One reason for this is the urban heat island effect, where urban areas are several degrees hotter than surrounding natural areas because of all of the heat-absorbing surfaces like roads and buildings. More than half of the human population lives in cities, and as they heat up, it is especially important to understand how some species adapt and even do better in urban environments. Urbanization and climate change can also increase the spread of invasive species. For example, some urban-adapted invasive species thrive in urban habitats that would otherwise be too cold for them to survive and reproduce in. Understanding how urbanization, climate change, and invasions interact can help us predict changes in biodiversity and species distributions in the future.

What We Did

The Australian redback spider, Latrodectus hasselti, is an invasive species of widow spider, native to Australia. Redback spiders are well-known in Australia for their bite and neurotoxic venom. Redbacks have been transported (likely accidentally along with used cars or produce) to Japan, New Zealand, the Philippines, Papua New Guinea, and India. We compared traits across native and invasive-habitat temperatures in a native population of spiders. The native spiders were collected from Sydney, Australia and the invasive population from Osaka, Japan, where redbacks became established in 1995.

Adult female Australian redback spider, Latrodectus hasselti (Image Credit: Sean McCann, CC BY 2.0)

We reared the spiders in the lab for three generations. We first checked for population differences in how spiders responded to extreme temperatures, measuring the lowest and highest temperatures at which spiders were able to maintain normal activity.

Next, we investigated how spiders respond to more moderate temperature differences, such as those in autumn, right before overwintering. When female spiders from each population produced egg sacs, we put the egg sacs for two weeks in either Japan-typical (15 degrees Celsius) or Australia-typical (25 degrees) autumn temperatures, then put all egg sacs at 25 degrees until spiderlings emerged. We predicted that the invasive spiders from Japan would be better adapted to low temperatures than the native Australian population, as they’re used to colder temperatures. We also measured hatching success, development time, and body size.

Once the spiderlings were juveniles, we measured behavioural traits that may be important for survival in nature: boldness – how quickly a spider resumed movement after a simulated predator threat (a puff of air), and exploration – building a web in a new environment.

What We Found

At extreme high temperatures, spiders from each population were similarly tolerant, with females able to move at temperatures of up to 55 degrees Celsius! Surprisingly, males from the invasive population from Japan were less tolerant of extreme low temperatures, suggesting that they may not overwinter successfully in colder regions. Egg sacs from the Japanese population hatched equally well at low and high temperatures, but egg sacs from the Australian population failed to hatch more often at low temperatures. Native spiders also took longer to emerge from the egg sacs than invasive spiders at low temperatures, which could expose egg sacs to more predation risk.

The Japanese population was bolder and more exploratory at low temperatures, but less bold and less exploratory at high temperatures, whereas the native population was similarly bold and exploratory at both temperatures.

Problems?

Spiders from Japan, which live in cooler habitats, developed at both low and high temperatures, compared to a native population, which hatched less and developed more slowly when exposed to low temperatures. This study only tested one invasive and one native population, and it would be worthwhile to compare multiple invasive populations from both cooler and warmer habitats, as well as multiple native populations across Australia.

Although the invasive habitat in Japan is more extreme in temperature, spiders also live in more urbanized habitats compared to the native population. Urban habitats are hotter, and we would like to measure what conditions the animals are directly experiencing in the urban and natural habitats, to find out if spiders are able to colonize cooler climates because they thrive in urban heat islands habitats.

So What?

Some organisms may be better equipped to deal with changes we are facing with urbanization, habitat fragmentation, and climate change. In the case of Australian redback spiders, within twenty years, we found that an invasive population changed significantly in traits related to thermal performance, which may give them an advantage as temperatures change worldwide.

Behavioral traits are studied less frequently; finding increased variability in an invasive population may provide a clue to how the species can thrive in different environments. Understanding how organisms can establish and spread in environments different from their native ranges can help us predict which species will survive in our increasingly urbanized, changing world.


Dr. Monica Mowery is a Zuckerman STEM postdoctoral fellow in the labs of Yael Lubin and Michal Segoli at Ben-Gurion University of the Negev. She received a B.S. in biology and community health at Tufts University, working on butterfly visual signals and behaviour in Sara Lewis’ lab. Her PhD was conducted in the labs of Maydianne Andrade and Andrew Mason at the University of Toronto Scarborough, where she studied invasion success in widow spiders. You can read more about Monica’s work at her website.

Light My Fire: How Birds Respond to Extreme Climate in the Wake of Bushfire

Fire, drought and flooding rains: The effect of climatic extremes on bird species’ responses to time since fire (2021) Connell et al., Diversity and Distributions, https://doi.org/10.1111/ddi.13287

The Crux

Both bushfires and extreme climate events are capable of shaping not only habitats, but also the number of different species that inhabit them. Yet the interaction between these phenomena can be equally important. For instance, an extreme flood or drought could have a very different impacts on a forest depending on how recently that forest was burned by fire. If a fire tore through recently, an extended period of drought may finish off species already under stress, yet if there has been a longer period of time since the last fire, the ecosystem may be able to tolerate a drought.

Given that climate change is increasing the occurrence of both extreme climate events and bushfires, it’s better to start investigating the effects of these interactions sooner rather than later. This week’s authors looked at the interaction between the two phenomena in south-eastern Australia, an area whose wildlife has come under a lot of pressure recently.

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The Unseen Effects of Habitat Loss

Whilst climate change continues to hog the limelight, habitat loss remains the key threat to biodiversity worldwide. And whilst events like the Australian bushfires obviously contribute to habitat loss, its main cause is land clearing, whether for agriculture, cattle grazing, mining or urbanization. No matter how many politicians deny or try to deviate attention from it, scientists have shown time and time again just how threatening habitat loss is to our planet’s biodiversity.

On the surface, the process seems quite simple. Habitat goes away, animals lose shelter and food. Yet this is just the tip of the iceberg. Many processes take place below the surface, cascading through an ecosystem. So let’s have a look at the manifold effects of habitat loss, and why it’s the greatest threat to biodiversity today.

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5 Stages of Grief and the Australian Wildfires

Image Credit: Bert Knottenbeld, CC BY-SA 2.0, Image Cropped

In case you’ve been living under a rock (in which case, stay there, there’s probably less smoke), you’ll know by now that Australia has experienced wildfires over the last couple of months that dwarf what California and the Amazon went through last year.

The Australian bush fires have been widely covered in the media, but let’s do a quick summary of the stats^. Earlier this week, approximately 73,000 square kilometres – around the size of Belgium and the Netherlands combined – have been burnt and over a billion mammals, birds and reptiles have likely been killed. Tragically, 24 people have died as of Monday, three of whom were volunteer firefighters.

So how has the nation – and the world – reacted? The spectrum has been vast, making analysing the reaction no easy task. So today I wanted to have a look at Australia’s (and in a sense the world’s) ongoing reaction to the Australian bushfires as per the Kubler-Ross Five Stages of Grief.

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Science in Practice: Highlights from the Ecological Society of Australia’s 2019 Annual Meeting

The Cataract Gorge in Launceston, Tasmania, where the 2019 Ecological Society of Australia Annual Meeting was held (Image Credit: Marina Schmoeller, CC BY 2.0)

I just got back from 10 days in Tasmania, Australia. As a temporary visitor in the country, I extended my trip to attend the Ecological Society of Australia’s annual conference (ESAus) as much as I could, so I could explore the surroundings and get to know a little of the place, its people and its unique biodiversity.

The conference was held in Launceston, the second largest city in Tasmania. With about ninety thousand inhabitants, a rich history with deep roots in its eye-catching landscapes, the Tamar River Valley and the Cataract Gorge, Launceston is a charming place with a lot to offer all visitors. But let’s talk about the conference.

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What Being Functionally Extinct Means, Why Koalas Aren’t, and Why Things Are Still Pretty Dire

Image Credit: Swallowtail Grass Seeds, Public Domain Mark 1.0, Image Cropped

There has been a lot of recent (and well deserved) press surrounding the bush fires in Australia. Because of these fires countless animal and plant life has been lost, and the most visible example of that are the koalas. You probably saw the video of a woman running into a burning area to save a koala from the fire*. Unfortunately, most of the koalas didn’t have people around to save them and over 1,000 are estimated to have died. Because of this a group has claimed that koalas are now “functionally extinct”, and the press has run with this claim. While it is unfortunate that this misinformation spread so quickly and so widely, the good news is that koalas are in fact NOT functionally extinct. Great! But what does being “functionally extinct” mean? 

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The Perfect as the Enemy of the Good in Sustainable Living

Eating beef isn't great for the environment. But ca someone who occasionally snacks on cows still be in favour of conservation and other ecological causes?

Eating beef isn’t great for the environment. But can someone who occasionally snacks on cows still be in favour of conservation and other ecological causes? (Image Credit: Gellinger, Pixabay licence, Image Cropped)

Today I want to talk about a tweet. Or more accurately, the attitude to sustainability that this tweet represents. It occurred during the recent Ecological Society of Australia conference, and went roughly thus*.

Good to see only vegetarian food at ESA2018. We know that it’s not possible to be truly in support of conservation unless you cut meat out of your diet.

Now for starters, I want to make it clear that I am 100% in support of eating vegetarian. For those of us fortunate enough to be living in relative affluence, vegetarian diets are easy to maintain, generally cheaper (based on personal experience), and have a proven positive impact on the climate. I’m not completely vegetarian, but I take a lot of steps to minimise my diet’s climate footprint. It doesn’t take much.

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Lessons From a Long History of Fish Invasions

The European Perch, brought for angling by earlier settlers, has had severe effects on a number of native Australian fish (Image Credit: Karelj)

Transport pathways shape the biogeography of alien freshwater fishes in Australia (2018) Garcia-Diaz et al., Biodiversity Research, DOI: 10.1111/ddi.12777

The Crux

Invasive species are a problem in every type of ecosystem, be it by reduction of local diversity, or negative effects on a region’s economy or human health. Freshwater rivers and lakes are no exceptions to this. Invasive fish have impacts on local habitats which include outcompeting or just flat out eating local species, changing a habitat’s entire structure (say by clearing away aquatic vegetation or increasing pH levels) and the reorganisation of the entire population of a lake or river, from the birds that nest on the shoreline to the tiny planktonic species that are the base food source of the entire ecosystem. Once an invasive species is established, it can be impossible to remove.

So naturally, understanding where and how invasive species are likely to strike is of huge benefit. This paper tries to map that out, using Australia as a case study. It’s a great example; Australia has a long history with invasive species, and this study alone looks at 33 different types of invasive fish.

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