Can a simple game of rock, paper, scissors explain competitive interactions in grasslands?
Highlighted by Jennifer Firn
Hautier Y, Vojtech E, Hector A. The importance of competition for light depends of productivity and disturbance. Ecol Evol. 2018;8:10655-10661. https://doi.org/10.1002/ece3.4403
When I first read Hautier et al’s paper in Science in 2009 I had just finished my PhD which included a large competition glasshouse trial that took me three failures, several small grants pieced together to afford to keep going and my findings were nowhere even close to the ground breaking research they published. Glasshouse experiments are tough! I remember reading their paper and thinking …wow their results are exciting, but the experimental approach could only be described as ingenious— why did I not think of this! Why had no one else thought of this idea before?
In a 2018 study published in Ecology and Evolution, Hautier, Vojtech and Hector examine again under controlled glasshouse conditions how competition for light changes depending on soil fertility but build on this by considering what happens when disturbance is thrown into the mix.
To do this, they use a model system of five perennial grass species:
- Alopecurus pratensis,
- Anthoxanthum odoratum,
- Arrhenatherum elatius,
- Festuca rubra, and
- Holcus lanatus.
They established five monocultures, all 10 pairwise mixtures and single full five-species mixtures in a fully randomized design. Each species combination was replicated five times, totalling 80 plots. Treatments included productive, unproductive (created by adding sucrose to the soil) and disturbed (frequent cutting).
This study confirms their previous findings that as productivity (rock) increases competition shifts from nutrients to light (paper)—asymmetric competition—but then furthers our understanding of these mechanisms by showing that disturbances (scissors) that prevent prevents canopy closure elevate this shift and competition remains belowground for nutrients. Another clever contribution to understanding plant community assembly.
Gulls can count on drones
Highlighted by Chris Foote
Rush GP, Clarke LE, Stone M, Wood MJ. Can drones count gulls? Minimal disturbance and semiautomated image processing with an unmanned aerial vehicle for colony-nesting seabirds.
Ecol Evol. 2018;8:12322–12334. https://doi.org/10.1002/ece3.4495
The recent closure of Britain’s Gatwick airport due to a rogue drone was a reminder of the potential negative effects of this new technology. For ecologists however, the increasing affordability of remote-piloted drones provides opportunities to improve monitoring of wildlife populations.
Drones could particularly help with monitoring seabirds. With many populations in severe decline, obtaining accurate counts of breeding colonies is crucial for seabird conservation. However, ‘traditional’ counts by human observers suffer from lack of accuracy, observer bias, and the logistical difficulties caused by seabirds often breeding in remote and hard-to-access locations. There is also a risk that the presence of human observers disturbs colonies; there is evidence that such disturbances can cause increased nest abandonment and chick predation.
Drones would appear to provide an obvious solution to these issues, able to easily and (relatively) cheaply survey an entire colony with minimal disturbance. However, there are issues around ensuring data quality and in managing and analysing the substantial amount of data drones produce. Beyond this there is the possibility that the drones themselves disturb the gulls; especially important as the lower drones fly over a colony, the better the quality of the resulting images. How low can a drone fly without disturbing gulls?
Graham Rush, Lucy Clarke, Meg Stone, and Matt Wood from the University of Gloucestershire looked to fill in these gaps with their study on a lesser black-backed gull colony located on Stokholm Island off the coast of Wales.
They flew drones over the colony at varying altitudes to test differences in image quality and gull disturbance behaviour. Flying below 15 metres above ground level made no qualitative difference to image quality, while flights below 10 metres caused undue disturbance to the gulls. The study thus provides a clear sweet-spot for drone flights that provides good quality data without disturbing the gulls.
Comparisons showed that drones surveyed the gull colonies with comparable accuracy to human observers. The drones were even capable of distinguishing lesser black-backed gulls from their close relatives herring gulls and greater black-backed gulls.
The use of drones to monitor wildlife is far from novel anymore; a Google Scholar search for “drones and counting and wildlife” brings up over 7000 hits. However, increasing ubiquity of drone use makes papers like this all the more important. To avoid every research group having to reinvent the wheel – and to avoid inadvertent harm to the populations we seek to conserve – it is vital that work like this continues to be published.
Conserving the giant salamander
Highlighted by Gareth Jenkins
Chen S, Cunningham AA, Wei G, et al. Determining threatened species distributions in the face of limited data: Spatial conservation prioritization for the Chinese giant salamander (Andrias davidianus). Ecol Evol. 2018;8:3098–3108. https://doi.org/10.1002/ece3.3862
How to best conserve rare species is a challenge that we will increasingly face in the 21st century. Such species are often cryptic and already endangered, so by their very nature are hard to observe. One of the key questions that needs answering is how to approach this paucity of available data, which is usually absent at worst and often poor-quality at best.
A potential answer to this can be found in Chen et al. (2018), a recent publication in our journal that sought to address the lack of substantial data gathered on a critically endangered amphibian – the Chinese giant salamander. Populations of this charismatic creature have been decimated in fresh waters over the last half century, due to all-too-familiar factors such as habitat destruction and pollution. In addition, they are highly overexploited as a food source, with farmed salamanders commanding a premium and increasing poaching pressure on the wild populations.
As a result, available ecological observations are patchy and low resolution, with salamander range now highly fragmented. However, Chen and colleagues made the best of a bad situation – using existing environmental data to create habitat suitability models, which mapped with historical population records. They then tested their models on wide-ranging community surveys of historical salamander presence. Intriguingly, their approach predicted salamander populations at similar geographical localities to confirmed sightings. Indeed, the model suggests that suitable habitat still exists across vast swathes of China.
Approaches such as this have the potential to be applied to a wide range of endangered species, and show a pragmatic attitude to limited data sources. The authors freely admit they have data lacking, the presence reports were mostly decades old, and they relied at times on non-expert diagnosis. However, utilising whatever resources are available, in creative ways such as this, could well be crucial in informing how best to deploy conservation funds in ever more challenging financial conditions.
Single species studies often don’t find a home at international journals, but are certainly welcome at Ecology & Evolution for reasons just like this.