Bram was part of a working group hosted by the German Integrative Biology Institute in Leipzig that had the ambition to better understand how communities interact in space by including a much needed temporal dimension. In a first paper lead by Patrick Thompson, we present a novel framework to understand (and study) how ecological communities can interact in space and how this leads to different temporal dynamics in community data. Instead of trying to infer process from community patterns, this framework explicitly varies three underlying processes (density dependent competition, density independent environmental filtering and dispersal) and shows that by doing this a whole range of possible metacommunity dynamics can be obtained including all currently known and described dynamics as well as a range of dynamics that have remained unconsidered and unstudied.
We believe it can be an important first step to achieve a much needed synthesis in the field of metacommunity ecology.
The study was published as an “Idea and perspectives” piece in the journal Ecology Letters
The lab is active in Tanzania in an inter university collaboration with the Nelson Mandela Institute for Science and Technology in Arusha. In one of the first papers of this project, Grite Nelson shows that studies of river quality and integrity should cautiously infer the influence of surrounding land use activities. Water quality and biota responded to land use at differentn scales. What is more, the spatial buffers used to calculate land use had a strong impact on the detected land use effects. The work stresses the need to standardize approaches to investigate effects of land use on different aspects of river quality.
The paper is out in the journal Science of the Total Environment
Two years ago, Beth Turner did a MSc thesis in the lab and performed a field experiment in Nicaragua together with PhD student Mathil Vandromme. The goal was to demonstrate that prey species do not just respond to predators that are present in a certain habitat, but also to predators elsewhere in the landscape. To test this we used landscapes of bromeliads that have a central tank that provides aquatic habitat. As a predator we used a caged predatory larva of the mosquito Toxorynchites, a ferocious predator of mosquito larvae including members of its own species.
We could confirm that effects of predators in a natural ecosystem can extend beyond the patch in which the predator is present and that the presence or absence of remote predator effects on habitat selection depends on the distance to predators. The notion that perceived habitat quality can depend on conditions in neighbouring patches forces habitat selection studies to adopt a landscape perspective and account for the effects of both present and remote predators when explaining community assembly in metacommunities.
The work has been published in Journal of Animal Ecology
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
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
A moss island in the Sonian forest
Mario in the field (albeit not in the Sonian forest)
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.
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…
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.
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.