Tag Archives: worm

Incompetent Invaders Dilute Parasites and Alter Disease Dynamics

Guest post by Paula Tierney

Invasive freshwater fish (Leuciscus leuciscus) acts as a sink for a parasite of native brown trout Salmo trutta (2020) Tierney et al. Biological Invasions. https://doi.org/10.1007/s10530-020-02253-1

The Crux

From house cats to cane toads, invasive species are one of the biggest threats worldwide to native plants and wildlife, second only to habitat destruction. There are a few different definitions of an invasive species, but two consistent tenets are a) that they are a living organism spreading and forming new populations outside of their native range and b) causing some kind of damage to the native ecosystem, economy or human health. As humans move around the globe with increasing ease (these last two months aside), the spreading of invasive species is increasingly common in our globalised world.

The spread of invasive species creates new ecological interactions between native and invasive species that can impact how our native ecosystems function, including disease dynamics. One key set of interactions that can be completely changed by the introduction of the invader are that of parasites and their hosts. If development and transmission of native parasites is different in invasive hosts compared to their usual native hosts, the parasite dynamics of the whole system can be altered.

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Why Defining Biodiversity Matters in an Ecosystem

Forests such as Białowieska in Poland perform a wide range of functions, but if its biodiversity rises, how will this change? (Image Credit: Jacek Karczmarz, CC BY 3.0)

Biotic homogenization can decrease landscape/scale forest multifunctionality (2016) von der Plas et al., Proceedings of the National Academy of Sciences of the United States of America, 113

The Crux

Any ecosystem performs a multitude of functions, benefiting both the species that live in it and the humans who interact with it, from litter decomposition to resistance of drought to timber production. As such, maintaining high levels of ecosystems is a well-studied concept, and it has been posited that high levels of biodiversity increase the levels functions an ecosystem can perform, or its multifunctionality.

But while the word biodiversity is recklessly bandied about these days, scientifically it’s a somewhat vague term. At an ecosystem level, you may have patches of very high local (or alpha) diversity, but the turnover of species between patches (beta diversity) might be quite low. The variation in types of biodiversity may influence your ecosystem multifunctionality. For instance, patches of high alpha diversity might lead to high levels of functionality in some patches, but little functionality elsewhere, whereas high levels of beta diversity may lead to low levels of functionality, but many functions. This paper investigates relationships between different biodiversity levels and ecosystem multifunctionality.

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