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
In joint work with the University of the Free State, we study how isolated mountains and rocky outcrops can help to preserve biodiversity. As study region we work in the grassland biome of the Eastern Free State Province in South Africa. In a first paper, now out in Biological Conservation, we present data on the butterflies present in this region.
We found that butterflies in the landscape matrix between the mountains were a nested subset of species from the mountains and outcrops, and there was little evidence that species with certain traits were limited to either habitat. This suggests that species can retreat to mountain refuges during harsh conditions and recolonise the surrounding matrix once conditions improve.
Ecological refuges such as these mountains and rocky outcrops can unify land-sharing and land-sparing because their targeted protection would support the persistence of species throughout wider landscapes.
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
Annual fishes of the genus Nothobranchius are endemic to temporary ponds. When exposed nonlethally to a predation risk, their reproductive efforts are increased, likely to reproduce as much as possible before being predated upon.
This experiment was done by Arnout Grégoir, who recently defended his PhD. We are learning more about the interesting life histories of these remarkable vertebrates, that, in terms of certain life history aspects, have more in common with aquatic invertebrates than fish.
The paper is out now in Ecology & Evolution.
In a new paper Tom Pinceel shows that crustaceans from ephemeral water bodies have different egg hatching frequencies depending on local climatic conditions. If the climate is harsher and less predictable, a lower percentage of eggs hatches after rains. This ensures that more long lived eggs are left that may grow during future conditions!
The work has been published in Oecologia
In a new paper, Falko Buschke tried to test whether vertebrates that differ in conservation status differ in to what extent their ranges can be predicted by spatial and environmental gradients. It turns out there are no strong differences. Instead, models to predict the ranges of the most threatened species perform much worse than models for least concern species. Also, response to broad environmental gradients could not distinguish endangered, threatened or least concern species. This suggests that we may underestimate extinction risk of species if we would try to assess this based on reliance on specific environmental conditions.
The paper is out in Biodiversity & Conservation