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Mosquitoes make compromises – new paper in Ecology Letters

Tough decision making is not restricted to human societies. While male mosquitoes happily feed on the nectar in our gardens, female mosquitoes invade our bedrooms at night attracted by the proteins in our blood. They need this resource to produce eggs that are subsequently deposited in freshwater habitats where the larvae grow. However, not every pond or ditch is a good breeding ground and therefore gravid mosquitoes tend to be very picky. This is because mosquito larvae feature prominently on the menu of a whole range of predators such as fish and voracious larvae of water beetles and dragonflies. To ensure survival of their offspring, mosquito mums must therefore deposit their eggs in habitats where these killers are absent. It was already known that mosquitoes avoid the smell of fish when they are looking for a place to lay their eggs. However, in a new study in the journal Ecology Letters, we show that mosquitoes do not only avoid reproduction in local ponds that smell fishy, but also in neighboring fishless ponds in the surrounding landscape. Although several researchers have suggested that the smell of predators can be used as a chemical repellent to prevent mosquitoes from reproducing , we show that this may not work very well. If the smell of fish is everywhere, mosquitoes seem to be smart enough to realize that there are no better alternatives and happily lay their eggs, even if the environment smells fishy.  Just like politicians, mosquitoes seem to be able to make compromises and, in the absence of better options, will settle for a bad deal.

It was the first time that this process, which in the specialized literature is known as habitat compromise, could be demonstrated in nature. Releasing fish is a classical strategy to control mosquitoes. However, this approach is controversial as many biting mosquitoes reproduce in habitats where fish cannot survive such as ephemeral pools, gutters, buckets and other containers where rainwater accumulates. Additionally, releasing fish in ponds has negative effects on the diversity of other organisms. For instance, in Western Europe, a number of rare dragonfly species and amphibians such as the tree frog and the crested newt, can only successfully reproduce when their larvae are not consumed by fish. Yet, even when fish cannot be released, there are perspectives for the application of predator smell for mosquito control. Artificial fish smell chemicals might help to concentrate mosquitoes in a few selected water bodies in a landscape where the eggs and larvae can be eradicated locally. From an environmental perspective it will certainly be preferable to spray large areas with fish chemicals rather than insecticides. However, further research will be needed to confirm whether such an approach is practically feasible. The exact volatile fish chemicals to which mosquitoes respond are also still unknown.

The paper is out now in Ecology Letters

Mossing around

Mosses are more than just plants, for a wild variety of tiny animals, moss patches are veritable jungles. Yet, few animal ecologists have ventured into this world (but see and see). We did a first field survey to study spatial variation in biodiversity on moss islands that form on tree trunks. It was a small project that formed the BSc thesis of Mario Driesen and under supervision of Hendrik Trekels. In this pilot study we wanted to test whether typical island biogeography principles apply to moss islands. Despite the insular structure, small scale variation in isolation and island size don’t seem to matter for biodiversity. Canopy cover was the most important environmental variable. However, overall, we conclude that invertebrate composition in moss patches may not only depend on local patch conditions, in a particular moss species. It also depended on the presence of other moss species in the direct vicinity which can be dispersal sources of other species.

The work has been published in Acta Oecologica

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A moss island in the Sonian forest

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Mario in the field (albeit not in the Sonian forest)

Welcome Joren!

Joren Snoeks finished his MSc thesis at KULeuven and joins us to study the ecological and evolutionary role of ancient granite inselbergs in landscapes. Besides from his PhD, Joren will also teach a number of practicals in our BSc program.

Modeling the sensitivity to climate change

In a new paper out in Scientific Reports, we use a matrix population model to test how sensitive populations of fairy shrimps are to changes in climate. The stepwise modeling procedure allows to calculate the long term population growth as a measure of fitness. If it is positive, the population will survive, if it is negative it will not. It does this by calculating, for each generation, how many eggs would be produced based on known life history traits of the species and a measure of environmental quality of the inundation (in this case represented by inundation length).

For most species it is very difficult to know how they would respond to changes in climate. However, for our fairy shrimp we have a lot of background information that allows us to make educated guesses about which life history traits could be important. We know for this species that it requires a specific amount of time to reproduce which is related to how long a pool can hold water and on the conditions they need to hatch. We also know how much eggs they can produce per day, how many eggs hatch during each inundation etc…

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Population of the fairy shrimp Branchipodopsis wolfi in a temporary rock pool on a mountaintop in South Africa

The length of these inundations is one environmental parameter (of many) that will change under changing climates. But it is an important one that is directly linked to fitness. Shorter inundations means less inundations that are long enough for reproduction.

We were – and are – still ignorant about how these species will respond to these changes. However, the model does allow us to test which life history traits could be important to maintain long term survival of the populations. As such it shows which traits could help populations to survive.

One of the conclusions of the study is that, when inundations are short, it would be beneficial to make sure that a lower fraction of eggs would hatch during a given inundation. Such a mechanism could be an example of a risk spreading theory that is consistent with predictions of evolutionary bet hedging theory.

It is still a simplistic model, so it does not tell us how things will go in the future. It does not capture tradeoffs among life history traits nor the evolutionary potential of the populations.  Yet, it still narrows down the range of possible future scenarios of these populations by showing what the consequences for population survival would be if populations could respond adaptively or plastically and change there life history traits.

 

 

 

The scalability of macroecology

 

Falko wrote a great summary for his recent idea paper in Frontiers of Biogeography!

https://escholarship.org/uc/item/0bp2c1d0

russian-dolls

The Solitary Ecologist

Russian Dolls

No matter at which scale you look at it, nature is remarkable.

Like many others, I was taught ecology in a very hierarchical way: individual organisms are part of a wider populations of species, collections of species form communities and communities come together to make up ecosystems. Similarly, single trees are nested within forests, which aggregate to form biomes. I’m sure you can come up with many comparable examples.

The trouble with such neat spatial hierarchies is that they lure us into believing that if patterns appear similar at several different spatial scales, then the processes leading to these patterns should also be similar. It’s so easy to assume that nature is like a set of Russian Dolls: each daughter exactly the same as its mother, only slightly smaller. But this is not necessarily the case.

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New project in Tanzania

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A joint inter university collaboration was set up between the Flemish universities and the Nelson Mandela institute of Science and Technology in Arusha, Tanzania. The project was officially launched in September 2013. Within the project, which will run for at least six years, I will be supervising a PhD student working on the ecology of wetlands in the Pangani floodplain. The aim is investigate the impact of variation in hydrology and anthropogenic disturbance on wetland functioning and biodiversity, quantify ecosystem services and formulate more effective management strategies.

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Expedition to the Australian outback 2013

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Sunset at our campsite at Walga Rock

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Where we are going we don’t need roads

During the 2013 expedition we sampled a total of 600 rock pools from 50 inselbergs in Western Australia. The dataset wil be used to get more insight in the drivers of diversity patterns across spatial scales.

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Sampling a rock pool community on Baladgie Rock overlooking a salt lake

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A typical example of a West Australian inselberg in the Cue area in Western Australia

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