Ecosystem restoration strengthens pollination network resilience and function

Kaiser-Bunbury et al. 2017. Ecosystem restoration strengthens pollination network resilience and function. Nature 542,223–227

Figure 1 from the paper. The island of Mahé with study sites and pollination networks (for more details see the paper itself).


Kat Raines

I chose this article as it merges my past and present research areas. I currently work in radioecology, focussing specifically on pollinators in Chernobyl but previously I worked for three years in the Seychelles archipelago on invasive species projects focussing on everything from plants to mammals. I thought this paper looked interesting (although slightly out of my research field) and attempted to answer some of the big questions relating to ecosystem restoration in response to the removal of invasive species.

The aim of this paper by Kaiser-Bunbury et al. is to examine whether ecosystem restoration through the clearing of invasive plant species affects pollination networks. This study was undertaken as a community field experiment on the island of Mahé, Seychelles. The Seychelles archipelago is ideal to conduct invasive species projects as it is relatively isolated from other islands and main land Africa and Mahé offers mid altitude inselbergs as discrete sites from which 8 were selected for this study. Half the inselberg sites were cleared of invasive species and therefore referred to as restored and compared to sites that had not been restored. They found that restoration markedly changed pollinator numbers, behaviour, performance and network structure.

The authors noted that the removal of dense thickets from the restored sites could have had an effect and we wondered exactly how much this would affect pollinator’s ability to even see flowers and whether it was then appropriate comparing sites with dense vegetation to sites with a greater number of clear areas therefore increasing the visibility of flowers.

This study found that interactions in restored networks were more generalised and therefore indicate higher functional redundancy therefore making these networks more robust. This concept was a main point in the discussion for the group as we debated whether it was better to have a high number of specialised pollinators or whether it was better to be more generalised and to what extent this matters on an isolated island with a high number of endemic species. It has been shown that specialist species suffer from habitat loss the most and tend to go extinct first whereas more generalised species are more robust therefore increasing the ecosystem’s resilience. We also wondered if these findings could be extrapolated and applied to other regions and habitats as increased pollinator interaction is obviously a very important outcome for ecosystem restoration.

In conclusion we enjoyed the paper and were impressed with the amount of effort that went into data collection for the plant-pollinator networks. Ecosystem restoration is a powerful tool in conservation but it is relatively unknown what the effects of restoration are on ecosystem functions so this paper is a notable addition to that knowledge base.

Field work ethics in biological research

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Costello et al. 2016. Field work ethics in biological research. Biological Conservation. 203:268-271.


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Eilidh McNab

This week’s journal club, whilst focussed on a single article, was also a chance for the group to have a wider discussion around the ethics of field work.

Historically much natural history research has been undertaken through ‘collecting’ specimens – i.e. killing and preserving individuals. The scientific descriptions of most species on the planet come from ‘type’ specimens held in museums; the individual(s) from which the species is defined and named. Early ornithologists went out birding with shotguns, not binoculars. However, in recent decades this view of biological science has been gradually replaced by non-lethal methods (such as camera-trapping, DNA analysis, radio-tracking, etc.) and the use of fatal collecting methods (certainly amongst vertebrates) is growing increasingly rare (aside from e.g. medical research, which I will not discuss here).

In this week’s paper, Costello et al. (all editors of the journal Biological Conservation, in which the paper is published) confront the ongoing issue of articles submitted to the journal that have, in their view, involved the unnecessary lethal collection of vertebrates, and have therefore been rejected for publication. The three recent examples that the authors discuss involved fish; in two instances researchers employed the use of gill-nets (which often lead to mortality of other non-target species as well), and in another there were very high rates of mortality due to tagging in a capture-release study. Importantly, in all instances the papers were not investigating a novel idea; instead they were simply showing well-understood phenomena in a different location. A table presenting a checklist of considerations for respectful conduct during field sampling highlights this as an important point; any negative impacts must be justifiable in terms of the advancement of scientific knowledge. However, as was pointed out in our debate on this paper, often it is not known what the results may be in advance of a study! Even fairly closely-related species can react very differently, and without first carrying out the field research this can’t necessarily be predicted.

Whilst lethal collecting or increased mortality due to methodology are the main topics, the paper discusses a number of other important issues surrounding field research. One of the first sections highlights the “uneven treatment of species”; and whether the relevant authorities (be they university ethics committees, or government officials) are more likely to allow lethal collection of one taxa over another. They ponder whether the case studies discussed involving fish would have been given permission had it been birds, mammals or reptiles involved – most likely not. This led to some discussion in the group about how much we understand about the way fish react to stimuli; a recent study looked at the use of compounds commonly used to euthanise laboratory zebrafish specimens, which was assumed to slowly send them to sleep. This compound was actually shown to drastically alter their behaviour prior to death, forcing the normally shade-seeking fish out into brightly lit areas of the tank. If this is the behavioural response, can we truly understand how the fish are reacting internally? And is it really as humane as was formerly thought?

Another important topic discussed within the paper was the impacts to non-target species that may result from any programme of fieldwork. This could include trampling (of vegetation or of e.g. invertebrates), or the transfer of invasive plant species or diseases (such as the fungus that causes white-nosed syndrome in North American bats, which has wiped out millions of individuals; the disease may have been inadvertently introduced by European-based cavers or bat ecologists).

The paper finished with a number of different solutions to the issues discussed. This included the use of low-impact methods where at all practicable, such as camera-traps, hair and faeces collection, drones, and observations. They also highlighted the importance of applying the ‘precautionary principle’ to research work, and to consider the possible impacts to the whole ecosystem being studied, not necessarily just the target species.

What is not really discussed in the paper is the perspective of different ‘types’ of researcher; for example a virologist may have a different view of lethal collecting to a conservation biologist. Another point that was brought up during our discussions, but is again not mentioned in the paper, is the cultural significance of certain organisms. Whilst a university ethics board may approve the lethal collection of a species, if it is viewed as particularly important, maybe even sacred, to native peoples in the study area, this should certainly be an important consideration for any researcher.

Whilst the paper is only three pages long, it succinctly covers a range of key considerations when planning any programme of field work. We concluded that this is an important paper to remind scientific researchers not just to fully explore all potential sampling methods before resorting to lethal collecting, but also to consider other potentially negative impacts that could be caused by the study. For example disturbance to other non-target organisms and the spreading of invasive species due to researcher movements should be considered prior to any research work. Whilst there were some comments that the paper may be viewed as a little ‘preaching to the converted’, the fact that multiple papers have been submitted to Biological Conservation that do not meet the ethical standards set by the journal highlights that it is still an important topic to discuss. This importance is highlighted by the fact that this article is one of the most downloaded from the journal in the last 90 days.

Join us this Friday when Matt Guy will lead a discussion on a recent paper in PloS ONE by Angell et al. entitled Sexual Segregation and Flexible Mating Patterns in Temperate Bats.

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0054194

External morphology explains the success of biological invasions

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Azzurro et al. 2014 External morphology explains the success of biological invasions. Ecology Letters 17: 1455-1463.


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Zarah Pattison

There is rarely a shortage of papers attempting to explain why particular species are more or less invasive than others. Since Charles Elton’s seminar work in 1958 (The Ecology of Invasions by Animals and Plants) there has been a rapid increase, particularly in the last 20 years, in publications surrounding the topic of invasion ecology. The silver bullet to help prevent invasions would be to determine which characteristics contribute most to invasion success and therefore enable us to predict the seriousness of an invasion for prevention and management. Azzuro et al. (2014) offered something a bit unique in their attempt to explain invasiveness by using the external morphology of species, fish species in this instance.

The aim of this study was to explore whether morphological traits could explain the abundance of introduced fish species entering the Mediterranean Sea via the Suez Canal. The Mediterranean Basin is suggested to have a monopoly of vacant niches, which may be contributing to the successful establishment of invasive species therein. Therefore the use of species morphology as a proxy for its ecological status in a community, could explain niche availability and the potential population increase post establishment.

Our initial thoughts were positive. The paper was written well, succinct and enjoyable. A large data set was used in an analysis which none of us had expertise in, but it was still clear what the authors were trying to achieve. (Very) basically a polygon encompassing the morphological space of the native fish community was used and the traits of non-native fish species were plotted across the native morphospace. The results showed that invasive non-native fish species were more abundant either outside or on the outer perimeter of the native morphospace where niche occupancy was low. Non-native species morphologically similar to native species, were less abundant and less likely to establish.

The paper definitely added to the breadth of our invasion ecology knowledge. However, like most studies in invasion ecology, the results are difficult to generalise. Negative caveats of many invasion ecology papers focused on specific species are just that: species specific and not amenable to generalisation. This can be frustrating from a conservation point of view. The authors themselves discussed the limitations of this study particularly in the case of invasive non-native lionfish (Pterois spp.) which has a rather unique morphology. Another point raised was that environmental conditions were not taken into account in this study, particularly fishing quotas which could lead to fluctuating populations regardless of native status. Additionally, life history/functional traits, which are used in many plant invasion studies, were not considered.

Overall the paper delivered its aim, but the title is very confident. Perhaps “External morphology can additionally explain the success of species specific biological invasions” would be more appropriate. However, we can’t test for everything in a study (we all know this!) and we all agreed this was a good piece of interesting science.

Join us next week where Eilidh McNab will lead a discussion of a paper recently published in Biological Conservation entitled: Field work ethics in biological research.

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