Tag Archives: Invasive Species

Dispersal In A Globally-Invasive Widow Spider

This is a guest post by Dr. Monica Mowery.

Title Image Credit: Sean McCann, CC BY 2.0, Image Cropped

Dispersal and life history of brown widow spiders in dated invasive populations on two continents (2022) Mowery et al., Animal Behaviour, https://doi.org/10.1016/j.anbehav.2022.02.006

The Crux

As I write this, I can hear invasive myna birds chirping in the trees outside, and see yellow pollen from the invasive Acacia trees floating through the air. What makes these species able to thrive far away from their native habitat? Despite the knowledge of how harmful invasive species can be, humans continue to transport species to new environments, both intentionally and unintentionally. Yet even with the explosive growth of both invasive species and invasion ecologists, we still don’t know a lot about which traits make the most successful invaders that can thrive and spread to new places.

One way to investigate this is to compare invasive populations that have just arrived at a new place, with populations that have been in an area for a long time. To better understand invasive species, we need to figure out how traits shift in invasive populations, as some individuals survive transport, establish, and spread to new habitats, expanding their range. When this happens, traits can change, or shift, as the species adapt to the new environment. Such traits, such as body size, number of offspring, and dispersal ability, may be particularly important during range expansion. This study is an investigation into how traits of invasive spiders shift on a broad geographic scale on two continents.

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How Invasives Get In Your Head (And Your Poop)

Image Credit: Hedera Baltica, CC BY-SA 2.0, Image Cropped

Invasive alien species as an environmental stressor and its effects on coping style in a native competitor, the Eurasian red squirrel (2022) Santicchia et al., Hormons and Behaviour, https://doi.org/10.1016/j.yhbeh.2022.105127

The Crux

We know that human activities can cause enormous stress for local species, and the introduction of invasive species is one of the most harmful stressors on a global basis. We know that new, harmful species can cause local extinctions, but how does their introduction affect the locals on a behavioural level?

Grey squirrels were introduced to Europe last century and have been spreading since, displacing the native red squirrels and wiping them out in many areas. This week’s authors wanted to know exactly how red squirrels’ behaviour changed when the grey squirrels were introduced, by looking in detail at the behaviour of red squirrles in both invaded and non-invaded areas, and seeing if they could see evidence of these changes in the expression of hormones (more on this in Did You Know).

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Of Course Climate Change Is A Threat To Global Ecosystems

Last week, prominent Australian conservation scientist Professor Hugh Possingham caused quite a stir when he stated that “personally [he is] not convinced that climate change is a huge threat to many species”. This naturally sparked heated debates among ecologists the world over, with varying levels of vitriol. As Dr. Charlie Gardner put it, it “is an extraordinary thing to hear from a leading conservation scientist”.

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Forecasting Foreign Fishy Futures

Forecasting the future establishment of invasive alien freshwater fish species (2021) Perrin et al., Journal of Applied Ecology, https://doi.org/10.1111/1365-2664.13993

The Crux

I know I write a lot about whether or not we should jump to conclusions about non-native species, but the fact is that there are lots of situations in which invasive species need to GO. Giving them the boot, however, can be a right pain, and more often than not it’s impossible.

But an ounce of prevention is worth a pound of cure (I don’t know the imperial system well so I assume that makes sense), and figuring out where an invader is likely to turn up means you can take measures to stop it happening in the first place. This saves a lot of hassle (and money) down the road.

So how do we figure out where invasives are likely to show up? That’s what this paper, which made up the first chapter of my thesis, aimed to find out, by looking at where invasive freshwater fish species have been popping up in Norway over the last 100 years.

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Charting The Spread Of Invasive Crayfish

Image Credit: Nature.Catcher, CC BY-SA 2.0, Image Cropped

Distribution and establishment of the alien Australian redclaw crayfish, Cherax quadricarinatus, in the Zambezi Basin (2021) Madzivanzira, South et al., Aquatic Conservation, https://doi.org/10.1002/aqc.3703

The Crux

While some of us may love certain seafood, and are willing to carry that seafood all over the globe, often the local species are none to happy about it. Such is the case with the Australian redclaw crayfish, a rare example of Australia finally delivering back to the world that which it has received so many of – an invasive species. The redclaw is actually one of nine crayfish that has been introduced to mainland Africa, and if their record (and the records of other crayfish species) is anything to go by, it could mean everything from the spread of parasites and complete ecosystem upheaval to severe damage to the local fishing industry.

It’s crucial to figure out exactly where invasives have spread to, and how quickly they’ve done it. It allows managers and conservation experts in other areas to prepare, and to keep an eye out. This week’s team tried to determine how quickly the crayfish are spreading from their introduction point in the Zembezi River Basin.

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The Summer of the Russian (Fish) invasion

Title Image Credit: Earl Steele, CC BY-NC-ND 2.0, Image Cropped

Every time fighter jets fly overhead here in Central Norway, either my wife or I nearly always make a dry remark about the Russians finally invading. It’s a slightly dark reference to former Norwegian occupations, but not something that’s likely to occur anytime soon.

Yet this summer, the papers were filled with constant sensational references to very real and ongoing Russian invasions. Luckily, they’re referring to the pink (or humpback) salmon, and not to any human army marching across the borders.

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Wild Horses Couldn’t Drag Me Away (From The Fact That They’re Invasive)

A mob of feral horses at Yarangobilly, Australia (Image Credit: Ian Sanderson, CC BY-NC 2.0, Image Cropped)

Horses are, without a doubt, a hugely significant part of human culture and history. Worldwide, they’ve played the role of food source, beast of burden, war steed, postal service, transport, and in modern times pet and sports star. Horses were and in many places still are are an omnipresent part of life. People have a lot of feelings about them.

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Introducing New Dung Beetles to Australia: Battling the Cane Toad’s Legacy

Image Credit: Dr Mary Gillham Archive Project, CC BY 2.0, Image Cropped

Last week, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) announced that they were going to import Moroccan dung beetles into Australia. The purpose being ostensibly to combat the fact that local Australian dung beetles have not evolved in step with marsupials instead of cattle, and are therefore pretty ineffective when it comes to breaking down the dung of sheep and cows. The introduction of the new beetles (specifically the Moroccan dung beetle, Gymnopleurus sturmi) is therefore intended to aid in the breakdown of cattle dung, returning nutrients to the soil, reducing the populations of the flies which follow cattle around and just generally cleaning the joint up. Sounds great. We’ve never had problems with species introduced to clean up our own mess before.

Read More: Dung Beetles with Benefits

Ok but didn’t you introduce the cane toads to sort out your problems and now they’re everywhere?

YES YOU’RE DAMN RIGHT WE DID. For those less familiar with the poster child for biological controls gone wrong, the cane toad (Bufo marinus) was introduced to Australia mid last century to deal with the cane beetle, which was destroying sugar crops. Australian species, having no experience which a poisonous frog of this type, have been heavily affected ever since, and the toads spread like lightning.

So this is a bad idea?

Well not exactly. While many people are comparing this directly to Australia’s previous mistakes, there are some marked differences. Exotic dung beetles have actually already been in Australia for decades. We do have 500 native species of dung beetle (accounting for about 10% of discovered species worldwide), yet scientists from the CSIRO introduced new species in the mid 60s to combat the same problem they’re trying to combat now.

This initial project is not exactly a great look for the CSIRO. In a paper from 2018, Bernard Doube of Dung Beetle Solutions International and formerly of CSIRO pointed out that of the 53 species that scientists attempted to introduce, ten were never introduced and 20 never successfully established. Doube attributed some of this to poor understanding of dung beetle breeding biology, which is worrying, given that we should really know as much as possible about a species before we go dropping it into a new ecosystem. The remaining 23 have spread to varying degrees throughout what was thought would be their natural range in a country like Australia. So far, they don’t appear to have posed a problem for native species, and have done their job in some areas.

So why will these new ones make a difference?

According to the CSIRO, the dung beetles that they have introduced don’t seem to get much work done during the spring. That’s why they’re introducing the new species. They’re not hyperfunctional crazy shitrolling juiced up beetle monsters, they just work a different shift.

This seems… fine?

Yeah ok, BUT IT’S NOT. I don’t actually have a problem with the science, it SEEMS pretty solid and anything that sequesters carbon needs to be given a look-in these days. But the way the CSIRO seems to have ignored the obvious questions that come with this irritates me. Even without reading into this too much, it is perfectly natural for anyone with a passing knowledge of the cane toad debacle to question it. The CSIRO needs to, right off the bat, acknowledge that this might sound like a bad decision, and then be abundantly clear about why it’s not.

This whole thing brings to mind the recent decision to introduce genetically modified mosquitoes into Florida to deal with the Zika virus. The science appears sound, but goddamn the concept of human-made super mosquitoes suddenly being released sounds like the start of a horror film we don’t want right now. As an example of how this sort of communication SHOULD be handled, mosquito ecologist Kara Fikrig posted a fantastic explanation of why the mosquito introduction should work, linked below.

I genuinely believe that science communication is getting better all the time. And I think this project sounds promising. I just wish that in articles like this one, and the one linked below (both of which do a pretty good job of communicating the science behind the project), both the media and the scientists would do a better job of addressing people’s valid concerns about the use of exotic species as biological invaders.

Read More: New dung beetle species set to help farmers reap benefits of turning poo into free fertiliser all year round


Sam Perrin is a freshwater ecologist who completed his PhD at the Norwegian University of Science and Technology who didn’t make a single poo joke for this entire article and deserves your respect because of it. You can read more about his research and the rest of the Ecology for the Masses writers here, see more of his work at Ecology for the Masses here, or follow him on Twitter here.

Ass-ets

Non-native species are often portrayed as villains – although not without reason as they can often cause more harm than good. The wild horses and donkeys in America’s west are no exception – both having a bad rep amongst landowners for trampling vegetation and competing with livestock and native species. But they do do some good as well – and I say this after putting my love for ponies aside.

Research has shown that these equids are actually very good diggers – specifically digging wells to tap into underground water sources. These wells create artificial oases across the arid landscape – meaning that other (native) species don’t have to travel as far to water sources, competition at water points is rdduced (no Lion King-esque waterhole dance numbers ’round here) as well as providing water to plant species.

While the fact that equids are providing water sources doesn’t erase the more detrimental effects that invasive species can have on the environment, it does show that they can help promote biodiversity in some cases. Maybe its a case of giving credit to the good that comes with the bad.

The original article can be found here:  https://doi.org/10.1126/science.abd6775

Do Disturbances Promote Biodiversity in the Presence of an Invasive Species?

Image Credit: Paresh Poriya, CC BY 4.0, Image Cropped (also not featuring tunicates)

Testing ecological theories in the Anthropocene: alteration of succession by an invasive marine species (2021) Christianson et al., Ecosphere, https://doi.org/10.1002/ecs2.3471

The Crux

Ecological disturbances, such as fire, floods, or storms, might seem like a catastrophe at first glance, but often they open up space for new species to take the place of dominant ones, creating a more diverse ecosystem. When a disturbance occurs matters as well – if a storm hits right before a particular species starts to reproduce, that species could take advantage of the extra space and become dominant in a short time.

In the 1970s, John Sutherland and Ronald Karlson tested this theory, looking at the invertebrate community of a coastal dock in North Carolina, USA. They found that which species dominated depended on when the community began to grow (a proxy for when disturbance opened up new space).

The area has since seen the introduction of an invasive species of tunicate, Clavelina oblonga. This week’s authors wanted to test whether the original patterns seen in the 1970s still showed up in the presence of the invader.

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