Oikos is a journal issued by the Nordic Ecological Society and is one of the leading peer-reviewed journals in ecology. Oikos publishes original and innovative research on all aspects of ecology, defined as organism-environment interactions.
Our cover for the June issue is a drawing made by Abby McBride. It summarizes the Forum paper "Inclusive fitness, asymmetric competition and kin selection in plants" by Bodil K. Ehlers and trine Bilde.
The drawing is one of five that Abby has made to illustrate our Forum section.
We are very happy to welcome Gregor Kalinkat to our editorial board! Read more about him in this interview!
What's you main research focus at the moment?
I just started a new position as a senior researcher in Franz Hölker's lab at the Leibniz-Institute for Freshwater Ecology and Inland Fisheries (IGB) Berlin. In this long-running (6 years!) interdisciplinary project funded by the German Federal Agency for Environment Protection (BfN) we are going to investigate ways to reduce negative effects of street lighting on insect communities. At this point I'm new to light pollution research but as it adds one more anthropogenic factor affecting food webs and ecosystems it integrates well with research I've been doing over the past years on climate warming and biological invasions. Notably, my new colleagues have published a very cool paper on how light pollution affects invertebrate food webs last year in Oikos https://onlinelibrary.wiley.com/doi/full/10.1111/oik.04696.
Can you describe your research career?
I started as a PhD student in the lab of Prof. Ulrich Brose in 2008, back then at the Technical University Darmstadt, Germany. We combined extensive laboratory experiments looking at feeding rates (i.e. functional responses) of cursorial invertebrate predators. We combined insights from these experiments with food web modelling to investigate the effects of body size on the structure and stability of terrestrial communities. One key paper of my PhD thesis was published in Oikos in 2011https://onlinelibrary.wiley.com/doi/10.1111/j.1600-0706.2010.18860.x. After I finished my PhD in 2012 I applied at my current institution in 2013 to bring my expertise in functional response experiments and methods to a project examining within-species variation in behavioral traits in fishes led by Dr. Max Wolf. After I spent a first short term postdoc at IGB and simultaneously tried to secure longer term funding for this research I then spent one year as a postdoc in the lab of Dr. Carlos Melián at the Swiss Federal Institute of Aquatic Science and Technology (eawag) where I started an investigation into temporal resolution and variability in a Baltic Sea food web based on a historical data set. In fall 2015 I returned to IGB with my own research project funded through the German Research Foundation (DFG) where since then I have been active in two broad research topics: (1) within-species variation in behavioral traits and its effects on predator-prey interactions and food webs as well as (2) the dire state of global freshwater biodiversity and what climate warming and biological invasions mean for it.
How come that you became a scientist in ecology?
When I started my undergraduate studies in biology my actual goal was to become a science journalist. But somehow I was so fascinated by lectures and practical courses on organismal biology and food web ecology that I decided to enroll as a PhD student in Uli Brose's group. I also guess some of the blame for me taking this route goes to the spectacular field trips organised back then by Prof. Stefan Scheu and Dr. Mark Maraun (the picture showing me with the sea star at night is from one of those field trips to the Mediterranean island of Giglio many years ago).
What do you do when you're not working?
Whenever possible I try to spend time with my family, I have two boys aged six and nine. I also love cycling, it's such a great way to get around, do your little workout and at the same time feel connected to nature.
Photo credit: The starfish photo is by Dorothee Sandmann and the soil sampling photo by Roswitha Ehnes.
We are very happy to welcome Ignacio Manuel Pérez-Ramos, Institute of Natural Resources and Agrobiology (IRNAS); Superior Council of Scientific Research (CSIC), Seville, Spain, to our editorial board. Get to know him a bit better in the interview below, and do visit his webpage: https://ignaciomperezramos.wixsite.com/perez-ramos
What's your main research focus at the moment?
My main research interests are focused in understanding and forecasting the responses of plant communities to projected changes of environmental conditions. To address this issue, I basically combine observational and experimental studies from a demographic and functional perspective. On the one hand, I have specialized in recruitment dynamics and characterization of regeneration niches in Mediterranean woody plant species, with special emphasis in the processes of seed production (“masting” phenomenon) and seed dispersal. On the other hand, I have acquired a solid background in functional ecology of Mediterranean plants with the aim of: (i) understanding the functional mechanisms exhibited by co-occurring species to persist under certain environmental conditions; and (ii) inferring several key ecosystem properties (such as net primary productivity, litter decomposition, nutrient mineralization rates, etc) under different scenarios of climate change. My main focus is on plant-plant and plant-animal interactions but I have recently moved towards understanding the role of soil microorganisms (bacteria, fungi, pathogens) in plant community assemblages and ecosystem functioning using a trait-based approach.
Can you describe your research career?
My research experience in the field of plant ecology started as an undergraduate student in the department of Plant Biology and Ecology (University of Seville). After finishing the degree in Biology, I obtained a FPU-fellowship for carrying out a doctoral thesis in the Superior Council of Scientific Research (IRNAS-CSIC), under the supervision of T. Marañón. As a PhD student, I specialized in recruitment dynamics and characterization of regeneration niches in Mediterranean woody plant species. After completing my PhD, I continued my research training at the “Centre d´Ecologie Fonctionnelle et Evolutive” (CEFE, CNRS) in Montpellier (France), working into the research group led by Eric Garnier and Catherine Roumet. During my postdoctoral period, I focused my research on plant functional adaptations to soil resource limitations and aboveground-belowground relationships. In addition, I could actively collaborate with other plant ecologists both at CEFE and at different centers of the “Institute National de la Recherche Agronomique” (INRA) in Montpellier and Toulouse. For example, with Florence Volaire (INRA-Montpellier), I conducted a glasshouse experiment on characterization of functional strategies of drought survival and root dynamics in Mediterranean plant species. Finally, I conducted a parallel project within the research group of Serge Rambal, focused on effects of climate change on recruitment dynamics of Quercus ilex, using the installations of a previous rainfall-exclusion experiment that was established in 2003 as a part of an European project.
Alter finishing my postdoctoral position in France, I returned to Spain thanks to different contracts. At present, I am enjoying a five-year contract within the prestigious and competitive "Ramón & Cajal" call at the IRNAS-CSIC. During these last years, I have led some projects focused in understanding and forecasting the responses of plants and soil microorganisms to different global-change drivers (e.g. climate change, changes in soil uses, invasion of exotic pathogens) using a multi-functional approach.
How come that you became a scientist in ecology?
I was always passionate about natural history. When I was a child, I remember myself spending a lot of time observing insects outdoors or transplanting plants from one pot to another in the terrace of my grandparents, whereas my friends were playing football or making mischiefs. So, it was always clear to me that I have to study Biology. After finishing the degree in Biology, I contacted different researchers in my homeland (Seville, Spain) and finally I had the opportunity to develop a PhD in the Superior Council of Scientific Research (IRNAS-CSIC).
What do you do when you’re not working?
When I am not working, most of the time I am looking after my kids and playing with them. I also enjoy travelling and trekking. My special interests also include photography, fishkeeping, bird breeding and bonsai collection. Since I consider myself a sociable animal, I love to spend my free time with my family and friends.
Anyone who has had an aquarium or a garden pond is likely to be familiar with the concept of water plants (macrophytes) helping to keep the water clean. In freshwater lakes, macrophytes are doing exactly that. Recall the lakes that you may have visited—you might notice that some have clear waters and lots of macrophytes, while others are turbid and with few or no plants. These may be examples of alternative stable states of shallow lakes, and macrophytes are known to stabilize the clear-water state (1).
This concept, however, has mainly been developed from observations in temperate areas, particularly Europe and North America. What about tropical and subtropical areas? Researchers previously thought that the effects of macrophytes in improving lake-water quality might be weaker in the tropics because of the vastly different community structures (2). Recent studies in low-latitude areas provide an opportunity to reassess and compare the effect of macrophytes on lake-water quality globally (Fig. 1).
Global distribution of the studies included in the meta-analysis. The study design is indicated by the shape and color of the symbols. The number of pairwise comparisons (n) in each study is indicated by the opacity of the symbols.
The effects have been measured in various ways, including comparing water samples from within and outside macrophyte stands; enclosing parts of lakes and manipulating the density of macrophytes; and comparing samples from the in-flow and out-flow of macrophyte wetlands. We synthesized the findings of 47 such studies by calculating and summarizing the Hedges’ g effect size, a quantitative measure of the magnitude of an effect.
We found, in general, that the positive effects of macrophytes on lake-water quality such as reducing the biomass of phytoplankton and lowering nutrient levels, hold true even when tropical and subtropical studies are included—despite not necessarily directly enhancing the clarity (measured by Secchi depth) (Fig. 2). Interestingly, when comparing the effects along a latitudinal gradient, we found that the macrophytes may be similarly effective or even more so towards lower latitudes (Fig. 3). We also found that the effects depend on the macrophyte growth form and the study design.
Mean Hedges’ g effect sizes and 95% confidence interval of the analyses of five metrics describing the effects of macrophytes on water quality. Chl: chlorophyll a concentration; TN: total nitrogen concentration; TP: total phosphorus concentration; SD: Secchi depth; TSI: trophic state index. Total numbers of pairwise comparisons (n) are denoted in parentheses. Each dot represents a pairwise comparison, and larger dots represent lower intra-study variance, which were used as a weighting factor in the analyses.
Effects of macrophytes on total phosphorus concentration across latitudinal gradients. Each dot represents a pairwise comparison, and larger dots represent lower intra-study variance, which were used as a weighting factor in the analysis. The regression line represents the fitted values from the meta-regression, and the grey ribbon represents the 95% confidence interval.
Why do these matter? The role of macrophytes in promoting the clear-water state is not only of theoretical interest, but highly useful in real life situations, namely the restoration of turbid lakes. While there have been several examples of using submerged macrophytes in temperate (3) and subtropical (4) lake restoration, our finding now encourages more investigation and experimentation in tropical and subtropical lakes.
Our mesocosm experiments in Singapore represent some of the most recent efforts to apply these findings, assessing the potential of macrophyte species in clearing water bodies dominated by cyanobacteria (5) (Fig. 4). The findings add to the growing line of evidence that macrophytes could be of great use in the restoration of (sub)tropical lakes.
I always am fascinated by the possibility of tweaking certain parameters and seeing their effects on a given process or a pattern. Experiments are usually my way of doing it. During my post-doc at iDiv, my office was next to a fungal ecologist-Ainhoa Martinez. We often talked about her work on the interaction between the two soil fungal species-both well known (arbuscular mycorrhizal fungi and Trichoderma), and both associated with benefitting plants. At the same institute, I met Christiane Roscher, who is well-known for her knowledge about the German flora. Imagine the luxury of having these experts next door. Forced by my “parameter tweaking” habit, I asked them if we could link the interaction of the two fungal species with the interaction among plants. The result was an experimental idea to test whether these two plant-friendly fungal species affect the interaction between several pairs of closely related (grassland) plants.
Picture 1: First week of experiment
Question driven experiments are full of thrills. We work hard to make sure experiments run well, harvest the experiment with colleagues, spend hours to collect the data and draw those first figures hoping for some cool results. There is another pleasure in experimenting with plants: Plants! Seeing them grow from seedling to flowering stage is just a phenomenal experience (Picture 1 and Picture 2).
Picture 2: Final week of experiment
One of our main results is that one of the fungal species (arbuscular mycorrhizal fungi) almost always outperformed the other fungi (Trichoderma) whether we grew them in plant monocultures or in plant pairs. The past work of Ainhoa also had indicated this, but in agricultural plants and only in their monocultures. This competitive interaction between the two fungi only relaxed competition in one plant pair among the several pair-wise plant competitions. We concluded that plant-plant interactions (the process) are inconsistently affected by the consistent competition between the two plant-friendly fungal species (the parameter tweak).
There is much to learn about how interactions at one level associate to the other. I believe that experiments will help us know about the right set of parameters and the tweaks. I would have never even thought of this question if I would not have Ainhoa and Christiane as office neighbors. Funnily, this experiment turned out also to be about plant and fungal neighbors.
Simple observations can sometimes lead to unexpected scientific discoveries. In 1996, wildlife biologist and educator Dick Thiel was musing about the abundance of North American porcupines (Erethizon dorsatum) near his home in central Wisconsin. That winter he started a mark-recapture study in nearby Sandhill Wildlife Area with help from secondary school students. In 2001, one of those students, Matt Schuler observed an unusual animal track while surveying part of the wildlife area. Matt and Dick confirmed that the track belonged to a fisher (Pekania pennanti), a predator that was extirpated from the region nearly 100 years ago, and began tracking both porcupines and fishers. Twenty years of data collected by hundreds of students revealed more than we expected about porcupine behaviour, nutrition, predation risk effects, demography, and evolutionary responses.
Porcupines are found across much of North America; from as far north as Alaska and as far south as Mexico. They are generally solitary animals that forage in tree canopies, and maintain dens in hollow trees or rock crevasses. Porcupines use quills to defend themselves from predators, but that does not mean they are immune to predation risk effects. The presence of fishers alters individuals’ foraging behaviours and can heighten physiological stress. Using data from Sandhill Wildlife Area, we learned that the combination of food, climatic conditions, non-consumptive effects of predation, and lethal predation all influence the nutritional state and recruitment of porcupines. Following these discoveries, we wondered: could these effects have lifetime fitness consequences?
We measured female growth and reproductive success before and after fishers recolonized the region, facilitating analyses of natural variation arising from both predation risk and environmental conditions. Our results indicate that individual females experiencing predation risk from fishers grew slower and gave birth to fewer offspring. Additionally, simulations show that predation risk alone can lead to population declines, and that populations can only grow when females invest more energy into reproduction or adult survival. If females only invest energy in juvenile survival, the population will continue to decline. Overall, we found that the accumulation of predation risk can reduce lifetime reproductive success in wild mammals. These results have wide reaching implications for the management and conservation of wild mammals, especially naïve populations experiencing increased predation risk from colonizing or invasive predators.
Dick answered his first question over a decade ago. However, more questions arose as students marked and recaptured porcupines each winter. Having seen how risk effects can affect porcupines, we wonder: how do individual risk effects contribute to the evolution and structure of other wild predator-prey systems?
Our study reports the results of the first broad-scale field study investigating the ecological role of Australia’s largest terrestrial predator, the dingo, in tropical savannah ecosystems. We did this by comparing the abundances of herbivores, an introduced mesopredator, small mammals and understorey vegetation structure at 7 sites spanning a 900 km transect. Each site consisted of a sub-site where dingoes were subject to lethal control and a sub-site where dingoes were not controlled.
Our findings provide evidence that apex predators shape ecosystems due to their suppressive effects on both herbivores and mesopredators. While these results are consistent with international research on trophic cascades they contrast with previous studies of apex predators effects in terrestrial ecosystems which have typically investigated the effects arising from their suppressive effects on herbivores and mesopredators in isolation. Our study provides evidence that apex predators’ suppressive effects on herbivores and mesopredators occur simultaneously and become manifest in the architecture and composition of ecosystems at large spatial scales
Water has a control over vegetation. Whether there is too much or too little of it, it has an impact on the spatial patterns of plants, mosses and lichens. This is evident in arid ecosystems – about but what about cold ecosystems which are considered as temperature limited systems?
Booming tundra heath, where there is plenty of plant-available water, but not too much. What a delicate balance! Photo: Julia Kemppinen
Fennoscandian mountain tundra is dominated by miniature prostate shrubs. But a closer look may reveal over 40 different vascular plant species in a single one square-meter plot. Here, plants are rather tiny, but nothing to compare to the mosses and lichens of this particular region. Solely in our study setting of 378 plots, we found all together 271 species of these three groups.
Rocky streams, the kingdom of mosses. Mosses prefer high water resources, and do not mind a little fluvial disturbance. Photo: Julia Kemppinen
We set out to investigate, just how important is water in its different aspects for these three ecologically and evolutionary distinct taxonomical groups. For this, we collected data on water as a resource, stress and disturbance, i.e. spatial and temporal variation of soil moisture and fluvial disturbance.
Our study setting on Mount Saana in northern Fennoscandia. Blue indicates high levels of soil moisture, yellow the opposite. Soil moisture is truly a fine-scale environmental variable, and this should be taken into account in vegetation research. Figure: Kemppinen et al. (2019) Oikos
Using a species distribution modelling approach, we found that the different water aspects proved to be crucial environmental drivers of fine-scale vegetation patterns. Water acts as a driver of vegetation not only on individual species level, but it also shapes community characteristics. And in this particular system and for these species, the importance of spatial variability of water exceeds the importance of soil temperature.
Some evidence on the fundamental role of water in fine-scale tundra vegetation patterns. GDD = growing degree day; RAD = radiation; SpH = soil pH; CRY = cryogenic processes; BIO = biota; WRE = water resources; WST = water stress; WDI = water disturbance. Figure: Kemppinen et al. (2019) Oikos.
Now we understand just how significant driver water is, even in this ecosystem of cool and rainy summers, where water resources are not scarce at all. It looks like these fundamental components of Arctic ecosystems – vascular plant, moss and lichen communities – will not only show sensitivity to warming temperatures, but they will also respond to altered water conditions.
The plentiful water resources of the high-latitudes are dependent on snow conditions. What will happen to fine-scale plant-available water in the future? Photo: Julia Kemppinen
The next step would be to understand how these fundamental fine-scale water aspects will be shaped by changing winter conditions and rising temperatures. Will there be ecological surprises ahead? How will these tiny tundra organisms cope? Thus, I declare an urgent need of more research on plant ecology and soil hydrology of tundra habitats under our rapidly changing climate.
Written by Julia Kemppinen on behalf of all co-authors
The first editor’s choice is the forum by Patrick & Yuan: ‘The challenges that spatial context present for synthesizing community ecology across scales’. The rationale for their forum is the common mismatch between community theory and its application within a landscape ecological context. Typically, the measurement of biodiversity patterns is highly dependent on the landscape context, while inference of the ecological and evolutionary processes that underlie those patterns are derived from theoretical perspectives that idealise landscapes. The authors bring this problem not only under attention; they also provide solutions to address this issue by resampling datasets to correct for variation in sampling density, spatial arrangement, and scale. Patrick & Yuan subsequently provide illuminating examples on how this proper resampling processes allows a profound understanding of the processes that shape ecological communities at landscape scales.
The meta-analysis ‘Belowground community responses to fire: meta‐analysis reveals contrasting responses of soil microorganisms and mesofauna’ by Pressler and collaborators is our second editor’s choice. With an increasing awareness of the importance of fires for many soil-ecological processes, the authors synthesised the evidence on soil microorganisms and mesofauna response to short fire disturbances. They compiled in this respect results from 131 empirical studies and demonstrate the overall strong negative effect of fire on soil biota biomass, abundance, richness, evenness, and diversity. Importantly, they also found soil mesofauna not to mirror the responses of soil microorganismsthat were subject to most research to date. In fact, soil mesofauna appear to be more resistant to fire than soil bacteria and fungi. While fire events are usually short, the ecological impacts may last much longer. The meta-analysis showed little resilience of especially the soil microbiota within 10 years after the fire disturbance event. The authors conclude their study with a discussion of the knowledge gaps and research priorities.