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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.

 

 

 

A big year

It has been a hectic year for most of us, not just for me. Roughly two years ago we started from scratch. No money, no projects, no equipment. Now a lab has emerged.  Last year field work was performed and animals were studied on and from five continents (Europe, Central America, Africa, Australia and SE Asia). I have seen more invertebrate orders and families last year than in any of the previous years. Elaborate field experiments were set up (Celina, Beth, Hendrik) sometimes with so many treatments that it was difficult not to get lost. We abandoned plankton as a core group and embraced more invertebrate and vertebrate groups than ever before. Our taxonomical expertise has increased tremendously and so has the literature we have on groups we never tackled before. Yannick and Hendrik made their own field guide for rock pool invertebrates from Western Australia, Mario personally made a key for invertebrates from moss islands in Belgium and nobody is more skilled in finding cryptic species than Gisela. I cannot tell you how much I appreciate this because this quality control and extra taxonomical resolution makes all the difference and allowed us to detect a lot of patterns that would have remained obscured otherwise.

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Many of you also did exceptional things to gather data. Some people crawled through dark holes full of feces (Barbara) to get data, others will face or have faced the treacherous mud of wetlands (Evelien, Lise). Some of you have used slave labor to collect samples and aid with lab work (Celina) or seduced Greek fishermen to get free transport (Sofie). Several of you have struggled with terrible bureaucracy, permits, tropical parasites or a combination of all four.  Some people said I was foolish to take on so many MSc students by the start of the year and they were right. But I was convinced by all of your plans and have not regretted it.

I’m also happy that overall we are doing well. Despite the fact that I never had less time to write papers than last year, we scored important  papers in Global Ecology and Biogeography and Scientific Reports… and strangely enough in Alzheimer’s & Dementia (don’t ask me how, I forgot). Our website got more than 10 000 unique visitors.

Valerio discovered something amazing in reptiles (I cannot write what, not published yet). Mathil got a PhD fellowship and lead a successful expedition into unknown territories. Evelien’s connectivity analyses are being explored in other systems and datasets from moss mites and coral reefs to pelicans. Karen found that predator avoidance strategies in the African savannah affect the shape of drinking holes and the vegetation around it… because antelope tend to approach water upwind to avoid being detected. With Melissa, we used a supercomputer to reconstruct interaction strengths in food webs. We build a matrix population model that showed that evolutionary bet hedging could help populations to cope with climate change. We joined the Bromeliad Working Group and are planning more exchange with Canada and Brazil. We used X rays to peer into the darkness inside the time capsules of dormant plankton and are only beginning to understand how they manage to use time travel to cope with environmental stochasticity. We are collaborating with Bio Engineers (the ecology of intracellular interactions), Physicists (optics), Archeologists (distribution models of ancient settlements) and Geographers (dispersal, urban ecology) on interdisciplinary research themes. These are just few of many highlights of my year.

Thanks to all my students and collaborators for helping us with starting up this lab!

Meeting of the Bromeliad Working group

In September, Mathil and I attended the meeting of the Bromeliad Working Group (BWG) in Paraty, Brazil. It was a great week with a lot of interesting talks, discussions and emerging collaborations.

This means we plan to do more work on bromeliads in the near future in Mathil’s and – hopefully – also Daniel’s PhDs and in collaboration with partners overseas.This will include work on spatial community dynamics as well as more applied work looking at ecosystem services provided by bromeliads. Within these research lines there will be opportunities to do MSc thesises. We will also try to get more funding for bilateral mobility between Brussels and partner institutions in Latin America such as Brazil.

Euraxes links: Brazil-Europe

We will add our community data from Bolivia and Costa Rica to the large database that is currently assembled by the BWG to support meta analyses across the continent. More info on the working group can be found on:

Bromeliad Working Group

Infinite thanks to Gustavo Romero, Vinicius Farjalla and Diane Srivastava for organizing a great symposium and for bringing all these people together!

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Enjoying the views in Rio

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Collective thinking

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Entering data into the database

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Washing up on the beach after the meeting

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Wrapping up results with Vinicius

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The streets of Paraty

Habitat selection in a bomb crater pond network

Foto copyright Tom De Bie

Bomb crater network in Hasselt (photo copyright Tom De Bie)

This summer, Hendrik is running a large scale mesocosm experiment to study habitat selection in aquatic insects. He put his cattle tanks in a unique location: a nature reserve that houses more than 100 bomb craters. These craters result from an attempt of the Americans to bomb the railwaylines in Hasselt during World War II. Now it is a remarkably diverse set of aquatic habitats.

Specifically for the experiment it is convenient that the system houses a substantial diversity of aquatic insects and that many pools are subject to drying which stimulates dispersal.

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Welcome Mathil!

As from October, Mathil Vandromme will join the research group after having succefully obtained a VLADOC PhD grant awarded by the Flemish Interuniversity Council for Developmental Aid. Mathil will start to work on the potential ecosystem services provided by bromeliad plants that grow in plantations of coffee and cocoa in Nicaragua. After completing her BSc at VUB, she enrolled in the Erasmus Mundus MSc programme in tropical ecology (TROPIMUNDO). During her MSc degree she worked on an elevational gradient in the Monteverde Cloud Forest in Costa Rica.

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Congratulations Dr. Jane Reniers

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After four years of frog hunting and intense experimenting, Jane Reniers defended her doctorate on amphibian life history strategies. The title of her doctorate was Managing Reproductive Challenges in Time Constrained Environments. Amphibian life history variation from clutch to landscape. I believe PhDs are all about managing challenges in a time constrained environment. And just like the amphibians she studied, Jane managed to overcome a lot of challenges and bad luck but still defended succesfully after just more than four years. A great job with a nice booklet to show for it… and a lot of great manuscripts still waiting to be published!

While she is moving on to new challenges, we will miss Jane’s spirit and laughter in the lab. But no doubt we will continue to collaborate to publish the remaining chapters of her PhD. We wish you all the very best Jane!

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The scalability of macroecology

 

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

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

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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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Congratulations dr Falko Buschke & dr Tom Pinceel

After just three years, Falko Buschke‘s Erasmus Mundus PhD fellowship came to an end. Just months later he succesfully defended his PhD thesis. Initially drawn to Belgium with the prospect of doing a thesis on community dynamics with a lot of empirical work, Falko soon settled into a different niche. Making use of the IUCN database he set out to explain the distribution patterns of terrestrial vertebrates in Africa. For this he used a very diverse set of statistical tools. He reconstructed biogeographical patterns in Africa based on how species present in different locations respond to spatial and environmental gradients. He experimented with novel ways to define regional species pools and investigated the drivers of patterns of alpha and beta diversity. Finally, he also experimented with spreading dye models and built a neutral metacommunity model to explain different biogeographical patterns in this  realm. Overall, it was an exciting journey exploring the interface between community ecology and macro ecology.  Falko, it was great having you here.  We will miss your wit and humour now you have returned to South Africa… and will continue to follow your adventures on  http://solitaryecology.com/

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Just two weeks later, Tom Pinceel joined Falko in the league of doctors. After doing a MSc working on genetic patterns in rock pool fairy shrimp, Tom continued along this path and started to explore the hatching strategies of these enigmatic inhabitants of temporary pools worldwide. Tom showed adaptive variation in hatching strategies of pool invertebrates along a gradient of habitat stability. He also revealed that the ancient diversification of fairy shrimp on the Australian continent coincided with a period of intense aridification. When Australia lost most of its rainforests, desert adapted fauna like fairy shrimps seem to have benefited and responded with a spectacular adaptive radiation. This resulted in a nice little booklet with most of his chapters already published. Tom is now continuing his research into delayed hatching as a survival strategy in extreme environments as a prospective post doc. We can only hope he will be able to continue his work in the near future.

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NEW PAPER: Exploring the link between ecology and biogeography in African vertebrates

In a new paper out in the journal Ecography, Falko Buschke tried to explain the distribution patterns of all terrestrial vertebrates that occur in sub Sahara Africa using environmental variables and spatial dispersal related variables.

He found that when you map Africa based on how much variation is explained by dispersal based processes vs. environmental niche based filtering, you can see the contours of the biogeographic regions. This suggests that community structuring processes differ among regions within biogeographic realms.

He also showed that corrections for range size are necessary to extract ecologically meaningful patterns from variation partitioning results.

Finally, he found that unexplained variation was highest in species with small distributions… which is worrying from a conservation perspective as these are often threatened. While we can quite accurately predict distributions of widespread animals, we don’t know very well why certain rarer species are range restricted.

http://onlinelibrary.wiley.com/doi/10.1111/ecog.00860/abstract

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An African Black Rhino. One of the species in Falko’s database.

NEW PAPER: Simulating the effects of climate change on habitat suitability and connectivity in a pond metacommunity

In a new paper published in Freshwater Biology, PhD student Karen Tuytens builds further on a hydrological model for temporary pools I developed in my PhD. Temporary pools are expected to be strongly impacted by the effects of global environmental change. Being directly dependent on precipitation (and occasionally ground water) for filling, changes in precipitation and/or evaporation will have an impact on the length (hydroperiod) and the frequency of inundations.

http://onlinelibrary.wiley.com/doi/10.1111/fwb.12319/abstract

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The model that was developed is a realistic simulation model which can be parametrized for individual pools and which can predict the water levels on a day to day basis based on nothing but pool morphometry and precipitation and evaporation data. By making use of historic climate it is possible to reconstruct the inundation history of a pool and, hence, reconstruct the long term disturbance regime which is relevant to explain both patterns of diversity as well as adaptive trait variation among populations.

However, the main advantage explored in this paper is the ability to simulate the effects of different IPCC climate change scenarios on inundation patterns. Karen did not only show that inundations are likely to be become shorter resulting in shorter growing seasons for aquatic fauna, she also modeled connections that are formed between pools during heavy rains. Under future scenarios that include less precipitation and higher evaporation, these connections formed less frequently. Overall, this shows that climate change can not only affect habitat suitability but also connectivity in clusters of aquatic habitats. This is relevant since different levels of connectivity can have pronounced effects, not only on the persistence of populations but also on diversity and the functioning of metacommunities.

The code of the model is optimized for the R programming environment and is readily available in the appendix of the paper. At the moment, the model is optimized to work in very simple aquatic habitats such as rock pools which have no groundwater influence and don’t leak water. However, Karen is currently extending the model to make it applicable for more complex temporary aquatic habitats such as temporary wetlands.

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